Picture of the Week

15 May 2023: The densely packed globular cluster NGC 6325 glistens in this image from the NASA/ESA Hubble Space Telescope. This concentrated group of stars lies around 26 000 light years from Earth in the constellation Ophiuchus. Globular clusters like NGC 6325 are tightly bound collections of stars with anywhere from tens of thousands to millions of members. They can be found in all types of galaxies, and act as natural laboratories for astronomers studying star formation. This is because the constituent stars of globular clusters tend to form at roughly the same time and with similar initial composition, meaning that astronomers can use them to fine-tune their theories of how stars evolve. Astronomers inspected this particular cluster not to understand star formation, but to search for a hidden monster. Though it might look peaceful, astronomers suspect this cluster could contain an intermediate-mass black hole that is subtly affecting the motion of surrounding …

8 May 2023: A vast galaxy cluster lurks in the centre of this image from the NASA/ESA Hubble Space Telescope. Like a submerged sea monster causing waves on the surface, this cosmic leviathan can be identified by the distortions in spacetime around it. The mass of the cluster has caused the images of background galaxies to be gravitationally lensed; the galaxy cluster has caused a sufficient curvature of spacetime to bend the path of light and cause background galaxies to appear distorted into streaks and arcs of light. A host of other galaxies can be seen surrounding the cluster, and a handful of foreground stars with tell-tale diffraction spikes are scattered throughout the image. This particular galaxy cluster is called eMACS J1823.1+7822, and lies almost nine billion light-years away in the constellation Draco. It is one of five exceptionally massive galaxy clusters explored by Hubble in the hopes of measuring the strengths of …

1 May 2023: The jellyfish galaxy JO175 appears to hang suspended in this image from the NASA/ESA Hubble Space Telescope. This galaxy lies over 650 million light-years from Earth in the appropriately-named constellation Telescopium, and was captured in crystal-clear detail by Hubble’s Wide Field Camera 3. A handful of more distant galaxies are lurking throughout the scene, and a bright four-pointed star lies to the lower right side. Jellyfish galaxies get their unusual name from the tendrils of star-forming gas and dust that trail behind them, just like the tentacles of a jellyfish. These bright tendrils contain clumps of star formation and give jellyfish galaxies a particularly striking appearance. Unlike their ocean-dwelling namesakes, jellyfish galaxies make their homes in galaxy clusters, and the pressure of the tenuous superheated plasma that permeates these galaxy clusters is what draws out the jellyfish galaxies’ distinctive tendrils. Hubble recently completed a deep dive into jellyfish clusters, specifically …

24 April 2023: A menagerie of interesting astronomical finds fill this image from the NASA/ESA Hubble Space Telescope. As well as several large elliptical galaxies, a ring-shaped galaxy is lurking on the right of this image. A pair of bright stars are also visible at the left of this image, notable for their colourful criss-crossing diffraction spikes. This collection of astronomical curiosities is the galaxy cluster ACO S520 in the constellation Pictor, which was captured by Hubble’s Advanced Camera for Surveys. This is one of a series of Hubble observations searching for massive, luminous galaxy clusters that had not been captured by earlier surveys. Appropriately, the proposal for observing time was named "They almost got away"! Astronomers took advantage of occasional gaps in Hubble's busy schedule to capture images of these barely-explored galaxy clusters, revealing a wealth of interesting targets for further study with Hubble and the NASA/ESA/CSA James Webb Space Telescope. Galaxy …

17 April 2023: The barred spiral galaxy UGC 678 takes centre stage in this image from the NASA/ESA Hubble Space Telescope. The spectacular galaxy lies around 260 million light-years from Earth in the constellation Pisces and is almost face on, allowing its lazily winding spiral arms to stretch across this image. In the foreground, a smaller edge-on galaxy seems to bisect the upper portion of UGC 678. Just like humans, stars have a natural lifecycle; they are born, grow up, and eventually grow old and die. Studying this stellar life cycle — usually referred to as stellar evolution — is an important topic for astronomers. The ends of star lives can be marked by truly spectacular events, including titanic supernova explosions, the creation of unimaginably dense neutron stars, and even the birth of black holes. UGC 678 was recently found to be host to one of these events; in 2020 a robotic telescope …

10 April 2023: Here we see JO204, a ‘jellyfish galaxy’ so named for the bright tendrils of gas that appear in this image to be drifting lazily below JO204’s bright central bulk. The galaxy lies almost 600 million light-years away in the constellation Sextans. This image was captured by the NASA/ESA Hubble Space Telescope, and it is the third of a series of Pictures of the Week featuring jellyfish galaxies. This series of images is possible thanks to a survey in which observations were made of six of these fascinating galaxies, including JO204. This survey was performed with the intention of better understanding star formation under extreme conditions. Given the dreamy appearance of this image, it would be understandable to wonder why jellyfish galaxies should be such a crucible for star formation. The answer is that — as is often the case with astronomy — first appearances can be deceiving. Whilst the delicate …

3 April 2023: The somewhat amorphous spiral galaxy UGC 2890 appears side-on in this image from the NASA/ESA Hubble Space Telescope, with bright foreground stars studding the image. This galaxy lies around 30 million light-years away in the constellation Camelopardalis. In 2009 astronomers spotted a catastrophically powerful supernova explosion in UGC 2890. While the supernova itself has long since faded from view, Hubble recently took a break from its regular observing schedule to inspect the aftermath of this explosive event. A Type II supernova is a spectacularly energetic explosion that marks the violent death of a massive star. As it runs out of the elements necessary to fuel nuclear fusion, the core of a massive star flickers out and stops producing energy. With nothing to support the crushing force of gravity, the core of the star shrinks and then suddenly implodes, leaving the star’s outer layers to collapse inwards and rebound out into …

27 March 2023: This luminous Picture of the Week shows Z 229-15 — imaged here in beautiful detail by the NASA/ESA Hubble Space Telescope — a celestial object that lies about 390 million light-years from Earth in the constellation Lyra. Z 229-15 is one of those interesting celestial objects that, should you choose to research it, you will find defined as several different things: sometimes as an active galactic nucleus (an AGN); sometimes as a quasar; and sometimes as a Seyfert galaxy. Which of these is Z 229-15 really? The answer is that it is all of these things all at once, because these three definitions have significant overlap. AGNs and quasars are both described in detail in the Hubble Word Bank, but in essence an AGN is a small region at the heart of certain galaxies (called active galaxies) that is far brighter than just the galaxy’s stars would be. The extra …

20 March 2023: The galaxy JW100 features prominently in this image from the NASA/ESA Hubble Space Telescope, with streams of star-forming gas dripping from the disc of the galaxy like streaks of fresh paint. These tendrils of bright gas are formed by a process called ram pressure stripping, and their resemblance to dangling tentacles has led astronomers to refer to JW100 as a ‘jellyfish’ galaxy. It is located in the constellation Pegasus, over 800 million light-years away. Ram pressure stripping occurs when galaxies encounter the diffuse gas that pervades galaxy clusters. As galaxies plough through this tenuous gas it acts like a headwind, stripping gas and dust from the galaxy and creating the trailing streamers that prominently adorn JW100. The bright elliptical patches in the image are other galaxies in the cluster that hosts JW100. As well as JW100’s bright tendrils, this image also contains a remarkably bright area of diffuse light towards …

13 March 2023: UGCA 307 hangs against an irregular backdrop of distant galaxies in this image from the NASA/ESA Hubble Space Telescope. The small galaxy consists of a diffuse band of stars containing red bubbles of gas that mark regions of recent star formation, and lies roughly 26 million light-years from Earth in the constellation Corvus. Appearing as just a small patch of stars, UGCA 307 is a diminutive dwarf galaxy without a defined structure — resembling nothing more than a hazy patch of passing cloud. This image is part of a Hubble project to explore every known nearby galaxy, giving astronomers insights into our galactic neighbourhood. Before this set of observations, almost three quarters of nearby galaxies had been investigated by Hubble in enough detail to spot the brightest stars and build up an understanding of the stars populating each galaxy. This Hubble project set out to explore the remaining quarter of …

6 March 2023: The irregular spiral galaxy NGC 5486 hangs against a background of dim, distant galaxies in this image from the NASA/ESA Hubble Space Telescope. The tenuous disc of the galaxy is threaded through with pink wisps of star formation, which stand out from the diffuse glow of the galaxy’s bright core. While this particular galaxy has indistinct, meandering spiral arms it lies close to the much larger Pinwheel Galaxy, one of the best known examples of ‘grand design’ spiral galaxies with prominent and well-defined spiral arms. In 2006 Hubble captured an image of the Pinwheel Galaxy which was — at the time — the largest and most detailed photo of a spiral galaxy ever taken with Hubble. NGC 5486 lies 110 million light-years from Earth in the constellation Ursa Major. Constellations are not only patterns of bright stars, but also a system that astronomers use to divide the sky into regions. …

27 February 2023: A jellyfish galaxy with trailing tentacles of stars hangs in inky blackness in this image from the NASA/ESA Hubble Space Telescope. As Jellyfish galaxies move through intergalactic space they are slowly stripped of gas, which trails behind the galaxy in tendrils illuminated by clumps of star formation. These blue tendrils are visible drifting below the core of this galaxy, and give it its jellyfish-like appearance. This particular jellyfish galaxy — known as JO201 — lies in the constellation Cetus, which is named after a sea monster from ancient Greek mythology. This sea-monster-themed constellation adds to the nautical theme of this image. The tendrils of jellyfish galaxies extend beyond the bright disc of the galaxy core. This particular observation comes from an investigation into the sizes, masses and ages of the clumps of star formation in the tendrils of jellyfish galaxies. Astronomers hope that this will provide a breakthrough in understanding …

20 February 2023: A massive galaxy cluster in the constellation Cetus dominates the centre of this image from the NASA/ESA Hubble Space Telescope. This image is populated with a serene collection of elliptical and spiral galaxies, but galaxies surrounding the central cluster — which is named SPT-CL J0019-2026 — appear stretched into bright arcs, as if distorted by a gargantuan magnifying glass. This cosmic contortion is called gravitational lensing, and it occurs when a massive object like a galaxy cluster has a sufficiently powerful gravitational field to distort and magnify the light from background objects. Gravitational lenses magnify light from objects that would usually be too distant and faint to observe, and so these lenses can extend Hubble’s view even deeper into the Universe. This observation is part of an ongoing project to fill short gaps in Hubble’s observing schedule by systematically exploring the most massive galaxy clusters in the distant Universe, in …

13 February 2023: A spectacular trio of merging galaxies in the constellation Boötes takes centre stage in this image from the NASA/ESA Hubble Space Telescope. These three galaxies are set on a collision course and will eventually merge into a single larger galaxy, distorting one another’s spiral structure through mutual gravitational interaction in the process. An unrelated foreground galaxy appears to float serenely alongside the collision, and the smudged shapes of much more distant galaxies are visible in the background. This colliding trio — known to astronomers as SDSSCGB 10189 — is a relatively rare combination of three large star-forming galaxies lying within only 50 000 light-years of one another. While that might sound like a safe distance, for galaxies this makes them extremely close neighbours! Our own galactic neighbours are much further away; Andromeda, the nearest large galaxy to the Milky Way, is more than 2.5 million light-years away from Earth. This …

6 February 2023: Right in the middle of this image, nestled amongst a smattering of distant stars and even more distant galaxies, lies the newly discovered dwarf galaxy known as Donatiello II. If you cannot quite distinguish the clump of faint stars that is all we can see of Donatiello II in this image, then you are in good company. Donatiello II is one of three newly discovered galaxies that were so difficult to spot that they were all missed by an algorithm designed to search astronomical data for potential galaxy candidates. Even the best algorithms have their limitations when it comes to distinguishing very faint galaxies from individual stars and background noise. In these most challenging identification cases, discovery has to be done the old-fashioned way — by a dedicated human trawling through the data themselves. The data that enabled these discoveries was collected by the Dark Energy Survey (DES), an intense …

30 January 2023: A snapshot of the Tarantula Nebula (also known as 30 Doradus) is the most recent Picture of the Week from the NASA/ESA Hubble Space Telescope. The Tarantula Nebula is a large star-forming region of ionised hydrogen gas that lies 161 000 light years from Earth in the Large Magellanic Cloud, and its turbulent clouds of gas and dust can be seen swirling between the region’s bright, newly-formed stars. The Tarantula Nebula is a familiar site for Hubble. It is the brightest star-forming region in our galactic neighbourhood and home to the hottest, most massive stars known. This makes it a perfect natural laboratory in which to test out theories of star formation and evolution, and a rich variety of Hubble images of this region have been released to the public in recent years. The NASA/ESA/CSA James Webb Space Telescope also recently delved into this region, revealing thousands of never-before-seen young …

23 January 2023: The bright variable star V 372 Orionis takes centre stage in this image from the NASA/ESA Hubble Space Telescope, which has also captured a smaller companion star in the upper left of this image. Both stars lie in the Orion Nebula, a colossal region of star formation roughly 1450 light years from Earth. V 372 Orionis is a particular type of variable star known as an Orion Variable. These young stars experience some tempestuous moods and growing pains, which are visible to astronomers as irregular variations in luminosity. Orion Variables are often associated with diffuse nebulae, and V 372 Orionis is no exception; the patchy gas and dust of the Orion Nebula pervade this scene. This image overlays data from two of Hubble’s instruments. Data from the Advanced Camera for Surveys and Wide Field Camera 3 at infrared and visible wavelengths were layered to reveal rich details of this corner …

16 January 2023: A host of astronomical objects throng this image from the NASA/ESA Hubble Space Telescope. Background galaxies ranging from stately spirals to fuzzy ellipticals are strewn across the image, and bright foreground stars much closer to home are also present, surrounded by diffraction spikes. In the centre of the image, the vague shape of the small galaxy UGC 7983 appears as a hazy cloud of light. UGC 7983 is around 30 million light-years from Earth in the constellation Virgo, and is a dwarf irregular galaxy — a type thought to be similar to the very earliest galaxies in the Universe. This image also conceals an astronomical interloper. A minor asteroid, only a handful of kilometres across, can be seen streaking across the upper left-hand side of this image. The trail of the asteroid is visible as four streaks of light separated by small gaps. These streaks of light represent the four …

9 January 2023: This image from the NASA/ESA Hubble Space Telescope features the galaxy LEDA 48062 in the constellation Canes Venatici. LEDA 48062 is the faint, sparse, amorphous galaxy on the right side of this image, and it is accompanied by a more sharply defined neighbour on the left, the large, disc-like lenticular galaxy UGC 8603. A smattering of more distant galaxies also litter the background, and a handful of foreground stars are also visible throughout the image. Have you ever wondered why the stars in Hubble images are surrounded by four sharp points? These are called diffraction spikes, and are created when starlight diffracts — or spreads around — the support structures inside reflecting telescopes like Hubble. The four spikes are due to the four thin vanes supporting Hubble’s secondary mirror and are only noticeable for bright objects like stars where a lot of light is concentrated on one spot. Darker, more …

2 January 2023: The scattered stars of the globular cluster NGC 6355 are strewn across this image from the NASA/ESA Hubble Space Telescope. This globular cluster lies less than 50,000 light-years from Earth in the Ophiuchus constellation. NGC 6355 is a galactic globular cluster that resides in our Milky Way galaxy's inner regions. Globular clusters are stable, tightly bound clusters of tens of thousands to millions of stars, and can be found in all types of galaxies. Their dense populations of stars and mutual gravitational attraction give these clusters a roughly spherical shape, with a bright concentration of stars surrounded by an increasingly sparse sprinkling of stars. The dense, bright core of NGC 6355 was picked out in crystal-clear detail by Hubble in this image, and is the crowded area of stars towards the centre of this image. With its vantage point above the distortions of the atmosphere, Hubble has revolutionised the study …

26 December 2022: The peculiar spiral galaxy ESO 415-19, which lies around 450 million light-years away, stretches lazily across this image from the NASA/ESA Hubble Space Telescope. While the centre of this object resembles a regular spiral galaxy, long streams of stars stretch out from the galactic core like bizarrely elongated spiral arms. These are tidal streams caused by some chance interaction in the galaxy’s past, and give ESO 415-19 a distinctly peculiar appearance. ESO 415-19’s peculiarity made it a great target for Hubble. This observation comes from an ongoing campaign to explore the Arp Atlas of Peculiar Galaxies, a menagerie of some of the weirdest and most wonderful galaxies that the Universe has to offer. These galaxies range from bizarre lonesome galaxies to spectacularly interacting galaxy pairs, triplets, and even quintets. These space oddities are spread throughout the night sky, which means that Hubble can spare a moment to observe them as …

19 December 2022: Just in time for the festive season, this new Picture of the Week from the NASA/ESA Hubble Space Telescope features a glistening scene in holiday red. This image shows a small region of the well-known nebula Westerhout 5, which lies about 7000 light-years from Earth. Suffused with bright red light, this luminous image hosts a variety of interesting features, including a free-floating Evaporating Gaseous Globule (frEGG). The frEGG in this image is the small tadpole-shaped dark region in the upper centre-left. This buoyant-looking bubble is lumbered with two rather uninspiring names — [KAG2008] globule 13 and J025838.6+604259. FrEGGs are a particular class of Evaporating Gaseous Globules (EGGs). Both frEGGs and EGGs are regions of gas that are sufficiently dense that they photoevaporate less easily than the less compact gas surrounding them. Photoevaporation occurs when gas is ionised and dispersed away by an intense source of radiation — typically young, hot …

12 December 2022: A portion of the open cluster NGC 6530 appears as a roiling wall of smoke studded with stars in this image from the NASA/ESA Hubble Space Telescope. NGC 6530 is a collection of several thousand stars lying around 4350 light-years from Earth in the constellation Sagittarius. The cluster is set within the larger Lagoon Nebula, a gigantic interstellar cloud of gas and dust. It is the nebula that gives this image its distinctly smokey appearance; clouds of interstellar gas and dust stretch from one side of this image to the other.Astronomers investigated NGC 6530 using Hubble’s Advanced Camera for Surveys and Wide Field Planetary Camera 2. They scoured the region in the hope of finding new examples of proplyds, a particular class of illuminated protoplanetary discs surrounding newborn stars. The vast majority of proplyds have been found in only one region, the nearby Orion Nebula. This makes understanding their origin …

5 December 2022: A small portion of the Small Magellanic Cloud (SMC) is pictured in this image from the NASA/ESA Hubble Space Telescope. The SMC is a dwarf galaxy and one of the Milky Way’s nearest neighbours, lying only about 200 000 light-years from Earth. It makes a pair with the Large Magellanic Cloud, and both objects can be seen from the southern hemisphere, as well as from some northern latitudes. The Small Magellanic Cloud contains hundreds of millions of stars, but this image focuses on just a small fraction of them. These stars comprise the open cluster NGC 376, which has a total mass only about 3400 times that of the Sun. Open clusters, as the name suggests, are loosely bound and sparsely populated. This distinguishes open clusters from globular clusters, which are often so thronged with stars that they have a continuous blur of starlight at their centres. In the case …

28 November 2022: Shreds of the luridly coloured supernova remnant DEM L 190 seem to billow across the screen in this image from the NASA/ESA Hubble Space Telescope. The delicate sheets and intricate filaments are debris from the cataclysmic death of a massive star that once lived in the Large Magellanic Cloud, a small satellite galaxy of the Milky Way. DEM L 190 — also known as LMC N49 — is the brightest supernova remnant in the Large Magellanic Cloud and lies approximately 160 000 light-years away from Earth in the constellation Dorado.This striking image was created with data from two different astronomical investigations, using one of Hubble’s retired instruments, the Wide Field Planetary Camera 2 (WFPC2). This instrument has since been replaced by the more powerful Wide Field Camera 3, but during its operational lifetime it contributed to cutting-edge science and produced a series of stunning public outreach images. The first of …

21 November 2022: The galaxy merger Arp-Madore 417-391 steals the spotlight in this image from the NASA/ESA Hubble Space Telescope. The Arp-Madore catalogue is a collection of particularly peculiar galaxies spread throughout the southern sky, and includes a collection of subtly interacting galaxies as well as more spectacular colliding galaxies. Arp-Madore 417-391, which lies around 670 million light-years away in the constellation Eridanus in the southern celestial hemisphere, is one such galactic collision. The two galaxies have been distorted by gravity and twisted into a colossal ring, leaving the cores of the two galaxies nestled side by side. Hubble used its Advanced Camera for Surveys (ACS) to capture this scene — the instrument is optimised to hunt for galaxies and galaxy clusters in the ancient Universe. Hubble’s ACS has been contributing to scientific discovery for 20 years, and throughout its lifetime it has been involved in everything from mapping the distribution of dark …

14 November 2022: A small, dense cloud of gas and dust called CB 130-3 blots out the centre of this image from the NASA/ESA Hubble Space Telescope. CB 130-3 is an object known as a dense core, a compact agglomeration of gas and dust. This particular dense core is in the constellation Serpens, and seems to billow across a field of background stars. Dense cores like CB 130-3 are the birthplaces of stars, and as such are of particular interest to astronomers. During the collapse of these cores enough mass can accumulate in one place to reach the temperatures and densities required to ignite hydrogen fusion, marking the birth of a new star. While it may not be obvious from this image, a compact object teetering on the brink of becoming a fully fledged star is embedded deep within CB 130-3. Astronomers used Hubble’s Wide Field Camera 3 to better understand the environment …

7 November 2022: The spiral arms of the galaxy NGC 7038 wind languidly across this image from the NASA/ESA Hubble Space Telescope. NGC 7038 lies around 220 million light-years from Earth in the southern constellation Indus. This image portrays an especially rich and detailed view of a spiral galaxy, and exposes a huge number of distant stars and galaxies around it. That’s because it’s made from a combined 15 hours worth of Hubble time focused on NGC 7038 and collecting light. So much data indicates that this is a valuable target, and indeed, NGC 7038 has been particularly helpful to astronomers measuring distances at vast cosmic scales. The distances to astronomical objects are determined using an interconnected chain of measurement techniques called the Cosmic Distance Ladder. Each rung in the ladder is calibrated by earlier steps, based on measurements of objects closer to us. This makes the accuracy of distances at the largest …

31 October 2022: This image from the NASA/ESA Hubble Space Telescope shows two of the galaxies in the galactic triplet Arp 248 — also known as Wild's Triplet — which lies around 200 million light-years from Earth in the constellation Virgo. The two large spiral galaxies visible in this image — which flank a smaller, unrelated background spiral galaxy — seem to be connected by a luminous bridge. This elongated stream of stars and interstellar dust is known as a tidal tail, and it was formed by the mutual gravitational attraction of the two foreground galaxies. This observation comes from a project which delves into two rogues’ galleries of weird and wonderful galaxies: A Catalogue Of Southern Peculiar Galaxies And Associations, compiled by astronomers Halton Arp and Barry Madore, and the Atlas of Peculiar Galaxies, compiled by Halton Arp. Each collection contains a menagerie of spectacularly peculiar galaxies, including interacting galaxies such as …

24 October 2022: This peculiar portrait from the NASA/ESA Hubble Space Telescope showcases NGC 1999, a reflection nebula in the constellation Orion. NGC 1999 is around 1350 light-years from Earth and lies near to the Orion Nebula, the closest region of massive star formation to Earth. NGC 1999 itself is a relic of recent star formation — it is composed of detritus left over from the formation of a newborn star. Just like fog curling around a street lamp, reflection nebulae like NGC 1999 only shine because of the light from an embedded source. In the case of NGC 1999, this source is the aforementioned newborn star V380 Orionis which is visible at the centre of this image. The most notable aspect of NGC 1999’s appearance, however, is the conspicuous hole in its centre, which resembles an inky-black keyhole of cosmic proportions. This image was created from archival Wide Field Planetary Camera 2 …

17 October 2022: The lives of newborn stars are tempestuous, as this image of the Herbig–Haro objects HH 1 and HH 2 from the NASA/ESA Hubble Space Telescope depicts. Both objects are in the constellation Orion and lie around 1250 light-years from Earth. HH 1 is the luminous cloud above the bright star in the upper right of this image, and HH 2 is the cloud in the bottom left. While both Herbig–Haro objects are visible, the young star system responsible for their creation is lurking out of sight, swaddled in the thick clouds of dust at the centre of this image. However, an outflow of gas from one of these stars can be seen streaming out from the central dark cloud as a bright jet. Meanwhile, the bright star between that jet and the HH 1 cloud was once thought to be the source of these jets, but it is now known …

10 October 2022: Terzan 1 is a globular cluster that lies about 22,000 light-years from Earth in the constellation Scorpius. It is one of 11 globular clusters that were discovered by the Turkish-Armenian astronomer Agop Terzan between 1966 and 1971 when he was working in France, based mostly at Lyon Observatory. Somewhat confusingly, the 11 Terzan globular clusters are numbered from Terzan 1 to Terzan 12. This is due to an error made by Terzan in 1971, when he rediscovered Terzan 5 — a cluster he had already discovered and reported back in 1968 — and named it Terzan 11. He published its discovery alongside those of Terzan 9, 10 and 12. He quickly realised his mistake, and attempted to have Terzan 12 renamed as Terzan 11. Unfortunately, he did not make it clear that Terzan 5 and Terzan 11 were one and the same, although another astronomer, Ivan Robert King, did publish …

3 October 2022: The two interacting galaxies making up the pair known as Arp-Madore 608-333 seem to float side by side in this image from the NASA/ESA Hubble Space Telescope. Though they appear serene and unperturbed, the two are subtly warping one another through a mutual gravitational interaction that is disrupting and distorting both galaxies. This drawn-out galactic interaction was captured by Hubble’s Advanced Camera for Surveys. The interacting galaxies in Arp-Madore 608-333 were captured as part of an effort to build up an archive of interesting targets for more detailed future study with Hubble, ground-based telescopes, and the NASA/ESA/CSA James Webb Space Telescope. To build up this archive, astronomers scoured existing astronomical catalogues for a list of targets spread throughout the night sky. By so doing, they hoped to include objects that had already been identified as interesting and that would be easy for Hubble to observe no matter which direction it …

26 September 2022: The stately sweeping spiral arms of the spiral galaxy NGC 5495 are revealed by the NASA/ESA Hubble Space Telescope’s Wide Field Camera 3 in this image. NGC 5495, which lies around 300 million light-years from Earth in the constellation Hydra, is a Seyfert galaxy, a type of galaxy with a particularly bright central region. These luminous cores — known to astronomers as active galactic nuclei — are dominated by the light emitted by dust and gas falling into a supermassive black hole. This image is drawn from a series of observations captured by astronomers studying supermassive black holes lurking in the hearts of other galaxies. Studying the central regions of galaxies can be challenging: as well as the light created by matter falling into supermassive black holes, areas of star formation and the light from existing stars all contribute to the brightness of galactic cores. Hubble’s crystal-clear vision helped astronomers …

19 September 2022: A bright young star is surrounded by a shroud of thick gas and dust in this image from the NASA/ESA Hubble Space Telescope. Hubble’s Wide Field Camera 3 inspected a young stellar object, over 9000 light years away in the constellation Taurus, to help astronomers understand the earliest stages in the lives of massive stars. This object — which is known to astronomers as IRAS 05506+2414 — is thought to be an example of an explosive event caused by the disruption of a massive young star system. If so, it would only be the second such example known. Usually the swirling discs of material surrounding a young star are funnelled into twin outflows of gas and dust from the star. In the case of IRAS 05506+2414, however, a fan-like spray of material travelling at velocities of up to 350 kilometres per second is spreading outwards from the centre of this …

12 September 2022: A glittering multitude of stars in the globular cluster Terzan 4 fill this image from the NASA/ESA Hubble Space Telescope. Globular clusters are collections of stars bound together by their mutual gravitational attraction, and can contain millions of individual stars. As this image shows, the heart of a globular cluster such as Terzan 4 is a densely packed, crowded field of stars — which makes for spectacular images! The launch of Hubble in 1990 revolutionised the study of globular clusters. The individual stars in these dense crowds are almost impossible to distinguish from one another with ground-based telescopes, but can be picked apart using space telescopes. Astronomers have taken advantage of Hubble’s crystal-clear vision to study the stars making up globular clusters, as well as how these systems change over time. This particular observation comes from astronomers using Hubble to explore Terzan 4 and other globular clusters to understand the …

5 September 2022: Two overlapping spiral galaxies are pictured in this image from the NASA/ESA Hubble Space Telescope. The two galaxies, which have the uninspiring names SDSS J115331 and LEDA 2073461, lie more than a billion light-years from Earth. Despite appearing to collide in this image, the alignment of the two galaxies is likely just by chance — the two are not actually interacting. While these two galaxies might simply be ships that pass in the night, Hubble has captured a dazzling array of interacting galaxies in the past. This image is one of many Hubble observations delving into highlights of the Galaxy Zoo project. Originally established in 2007, the Galaxy Zoo project and its successors are massive citizen science projects which crowdsource galaxy classifications from a pool of hundreds of thousands of volunteers. These volunteers classify galaxies imaged by robotic telescopes and are often the first to ever set eyes on an …

29 August 2022: The arms of the spiral galaxy M74 are studded with rosy pink regions of fresh star formation in this image from the NASA/ESA Hubble Space Telescope. M74 — also known as the Phantom Galaxy — lies around 32 million light-years away from Earth in the constellation Pisces, and is a familiar sight for Hubble.The beautiful reddish blooms that spread throughout M74 are huge clouds of hydrogen gas which are made to glow by the ultraviolet radiation from hot, young stars embedded within them. These regions — which astronomers refer to as H II regions — mark the location of recent star formation and are an important target for both space- and ground-based telescopes. Hubble’s Advanced Camera for Surveys, which collected the data in this image, even has a filter designed to pick out only this specific red wavelength of light! The data in this image come from a set of …

22 August 2022: The galaxy featured in this Picture of the Week has a shape unlike many of the galaxies familiar to Hubble. Its thousands of bright stars evoke a spiral galaxy, but it lacks the characteristic ‘winding’ structure. The shining red blossoms stand out as well, twisted by clouds of dust — these are the locations of intense star formation. Yet it also radiates a diffuse glow, much like an elliptical galaxy and its core of older, redder stars. This galactic marvel is known to astronomers as NGC 1156. NGC 1156 is located around 25 million light-years from Earth, in the constellation Aries. It has a variety of different features that are of interest to astronomers. A dwarf irregular galaxy, it’s also classified as isolated, meaning no other galaxies are nearby enough to influence its odd shape and continuing star formation. The extreme energy of freshly formed young stars gives colour to …

15 August 2022: This scintillating image showcases the globular cluster NGC 6540 in the constellation Sagittarius, which was captured by the NASA/ESA Hubble Space Telescope’s Wide Field Camera 3 and Advanced Camera for Surveys. These two instruments have slightly different fields of view — which determines how large an area of sky each instrument captures. This composite image shows the star-studded area of sky that was captured in both instruments’ field of view. NGC 6540 is a globular cluster, a stable, tightly bound multitude of stars. The populations of these clusters can range from tens of thousands to millions of stars, all of which are trapped in a closely-packed group by their mutual gravitational attraction. The brightest stars in this image are adorned with prominent cross-shaped patterns of light known as diffraction spikes. These astronomical embellishments are a type of imaging artefact, meaning that they are caused by the structure of Hubble rather …

8 August 2022: This celestial cloudscape from the NASA/ESA Hubble Space Telescope captures the colourful region surrounding the Herbig-Haro object HH 505. Herbig-Haro objects are luminous regions surrounding newborn stars, and are formed when stellar winds or jets of gas spewing from these newborn stars form shockwaves colliding with nearby gas and dust at high speeds. In the case of HH 505, these outflows originate from the star IX Ori, which lies on the outskirts of the Orion Nebula around 1000 light-years from Earth. The outflows themselves are visible as gracefully curving structures at the top and bottom of this image, and are distorted into sinuous curves by their interaction with the large-scale flow of gas and dust from the core of the Orion Nebula. This observation was captured with Hubble’s Advanced Camera for Surveys (ACS) by astronomers studying the properties of outflows and protoplanetary discs. The Orion Nebula is awash in intense …

1 August 2022: This star-studded image from the NASA/ESA Hubble Space Telescope shows the heart of the globular cluster NGC 6638 in the constellation Sagittarius. The star-strewn observation highlights the density of stars at the heart of globular clusters, which are stable, tightly bound clusters of tens of thousands to millions of stars. To capture the data in this image, Hubble used two of its cutting-edge astronomical instruments: Wide Field Camera 3 and the Advanced Camera for Surveys. Hubble revolutionised the study of globular clusters, as it is almost impossible to clearly distinguish the stars in globular clusters with ground-based telescopes. The blurring caused by Earth’s atmosphere makes it impossible to tell one star from another, but from Hubble’s location in low Earth orbit the atmosphere no longer poses a problem. As a result, Hubble has been used to study what kind of stars globular clusters are made up of, how they evolve, …

25 July 2022: This luminescent image features multiple galaxies, perhaps most noticeably LEDA 58109, the lone galaxy in the upper right. LEDA 58109 is flanked by two further galactic objects to its lower left — an active galactic nucleus (AGN) called SDSS J162558.14+435746.4 that partially obscures the galaxy SDSS J162557.25+435743.5, which appears to poke out to the right behind the AGN. Galaxy classification is sometimes presented as something of a dichotomy: spiral and elliptical. However, the diversity of galaxies in this image alone highlights the complex web of galaxy classifications that exist, including galaxies that house extremely luminous AGNs at their cores, and galaxies whose shapes defy the classification of either spiral or elliptical. The sample of galaxies here also illustrates the wide variety of names that galaxies have: some relatively short, like LEDA 58109, and some very long and challenging to remember, such as the two galaxies to the left. This is …

18 July 2022: This intriguing observation from the NASA/ESA Hubble Space Telescope shows a gravitationally lensed galaxy with the long-winded identification SGAS J143845+145407. Gravitational lensing has resulted in a mirror image of the galaxy at the centre of this image, creating a captivating centrepiece. Gravitational lensing occurs when a massive celestial body — such as a galaxy cluster — causes a sufficient curvature of spacetime for the path of light around it to be visibly bent, as if by a lens. Appropriately, the body causing the light to curve is called a gravitational lens, and the distorted background object is referred to as being "lensed". Gravitational lensing can result in multiple images of the original galaxy, as seen in this image, or in the background object appearing as a distorted arc or even a ring. Another important consequence of this lensing distortion is magnification, allowing astronomers to observe objects that would otherwise be …

11 July 2022: The globular cluster Terzan 2 in the constellation Scorpio features in this observation from the NASA/ESA Hubble Space Telescope. Globular clusters are stable, tightly gravitationally bound clusters of tens of thousands to millions of stars found in a wide variety of galaxies. The intense gravitational attraction between the closely packed stars gives globular clusters a regular, spherical shape. As a result, images of the hearts of globular clusters, such as this observation of Terzan 2, are crowded with a multitude of glittering stars. Hubble used both its Advanced Camera for Surveys and its Wide Field Camera 3 in this observation, taking advantage of the complementary capabilities of these instruments. Despite having only one primary mirror, Hubble’s design allows multiple instruments to be used to inspect astronomical objects. Light from distant astronomical objects enters Hubble and is collected by the telescope's 2.4-metre primary mirror; it is then reflected off the secondary …

4 July 2022: This NASA/ESA Hubble Space Telescope observation has captured the galaxy CGCG 396-2, an unusual multi-armed galaxy merger which lies around 520 million light-years from Earth in the constellation Orion. This observation is a gem from the Galaxy Zoo project, a citizen science project in which hundreds of thousands of volunteers classified galaxies to help scientists solve a problem of astronomical proportions — how to sort through the vast amounts of data generated by robotic telescopes. Following a public vote, a selection of the most astronomically intriguing objects from the Galaxy Zoo were selected for follow-up observations with Hubble. CGCG 396-2 is one such object, and was captured in this image by Hubble’s Advanced Camera for Surveys. The Galaxy Zoo project originated when an astronomer was set an impossibly mind-numbing task; classifying more than 900 000 galaxies by eye. By making a web interface and inviting citizen scientists to contribute to …

27 June 2022: This image from the NASA/ESA Hubble Space Telescope captures the sparkling globular cluster NGC 6569 in the constellation Sagittarius. Hubble explored the heart of this cluster with both its Wide Field Camera 3 and Advanced Camera for Surveys, revealing a glittering hoard of stars in this astronomical treasure trove. Globular clusters are stable, tightly bound clusters containing tens of thousands to millions of stars, and are associated with all types of galaxies. The intense gravitational attraction of these closely packed clusters of stars means that globular clusters have a regular spherical shape with a densely populated centre — as can be seen in the heart of this star-studded image. This observation comes from an investigation of globular clusters which lie close to the centre of the Milky Way. These objects have been avoided in previous surveys, as the dust spread throughout the centre of our galaxy blocks light from these …

20 June 2022: The massive galaxy cluster Abell 1351 is captured in this image by the NASA/ESA Hubble Space Telescope’s Wide Field Camera 3 and Advanced Camera for Surveys. This galaxy cluster lies in the constellation Ursa Major in the northern hemisphere. This image is filled with streaks of light, which are actually the images of distant galaxies. The streaks are the result of gravitational lensing, an astrophysical phenomenon that occurs when a massive celestial body such as a galaxy cluster distorts spacetime sufficiently strongly to affect the path of light passing through it — almost as if the light were passing through a gigantic lens. Gravitational lensing comes in two varieties — strong and weak — and both can give astronomers an insight into the distribution of mass within a lensing galaxy cluster such as Abell 1351. This observation is part of an astronomical album comprising snapshots of some of the most …

13 June 2022: This star-studded image shows the globular cluster Terzan 9 in the constellation Sagittarius, towards the centre of the Milky Way. The NASA/ESA Hubble Space Telescope captured this glittering scene using its Wide Field Camera 3 and Advanced Camera for Surveys. Globular clusters are stable, tightly bound groupings of tens of thousands to millions of stars. As this image demonstrates, the hearts of globular clusters can be densely packed with stars; the night sky in this image is strewn with so many stars that it resembles a sea of sequins or a vast treasure chest crammed with gold. This starry snapshot is from a Hubble programme investigating globular clusters located towards the heart of the Milky Way. The central region of our home galaxy contains a tightly packed group of stars known as the Galactic bulge, which is also rich in interstellar dust. This dust has made globular clusters near the …

6 June 2022: Like Sherlock Holmes’s magnifying glass writ large, the NASA/ESA Hubble Space Telescope has been used to peer into an astronomical mystery in search of clues. The enigma in question concerns the globular cluster Ruprecht 106, which is pictured in this image. While the constituent stars of globular clusters all formed at approximately the same location and time, it turns out that almost all globular clusters contain groups of stars with distinct chemical compositions. These distinct chemical fingerprints are left by groups of stars with very slightly different ages or compositions from the rest of the cluster. A tiny handful of globular clusters do not possess these multiple populations of stars, and Ruprecht 106 is a member of this enigmatic group. Hubble captured this star-studded image using one of its most versatile instruments; the Advanced Camera for Surveys (ACS). Much like the stars in globular clusters, Hubble’s instruments also have distinct …

30 May 2022: This image from the NASA/ESA Hubble Space Telescope shows the barred spiral galaxy NGC 7496, which lies over 24 million light-years away in the constellation Grus. This constellation, whose name is Latin for crane, is one of four constellations collectively known as the Southern Birds. The others are Pavo, Phoenix and Tucana, which depict a peacock, phoenix, and toucan respectively. The rest of the night sky is also home to a flock of ornithological constellations, including an eagle (Aquilla), swan (Cygnus), crow (Corvus), and dove (Columba). This image comes from a collection of observations delving into the relationship between young stars and the cold, dense clouds of gas in which they form. In addition to observations with Hubble’s Wide Field Camera 3 and Advanced Camera for Surveys, the astronomers behind this project gathered data using the Atacama Large Millimeter/submillimeter Array (ALMA), one of the largest radio telescopes in the world. …

23 May 2022: The muted red tones of the globular cluster Liller 1 are partially obscured in this image by a dense scattering of piercingly blue stars. In fact, it is thanks to Hubble’s Wide Field Camera 3 (WFC3) that we are able to see Liller 1 so clearly in this image, because the WFC3 is sensitive to wavelengths of light that the human eye cannot detect. Liller 1 is only 30 000 light-years from Earth — relatively neighbourly in astronomical terms — but it lies within the Milky Way’s ‘bulge’, the dense and dusty region at our galaxy’s centre. Because of that, Liller 1 is heavily obscured from view by interstellar dust, which scatters visible light (particularly blue light) very effectively. Fortunately, some infrared and red visible light are able to pass through these dusty regions. WFC3 is sensitive to both visible and near-infrared (infrared that is close to the visible) wavelengths, …

16 May 2022: This glittering gathering of stars is the globular cluster NGC 6558, and it was captured by the NASA/ESA Hubble Space Telescope’s Advanced Camera for Surveys. NGC 6558 is closer to the centre of the Milky Way than Earth is, and lies about 23 000 light years away in the constellation Sagittarius. Globular clusters like NGC 6558 are tightly bound collections of tens of thousands to millions of stars, and they can be found in a wide range of galaxies. As this observation shows, the stars in globular clusters can be densely packed; this image is thronged with stars in a rich variety of hues. Some of the brightest inhabitants of this globular cluster are surrounded by prominent diffraction spikes, which are imaging artefacts caused by starlight interacting with the inner workings of Hubble. Globular clusters equip astronomers with interesting natural laboratories in which to test their theories, as all the …

9 May 2022: This image from the NASA/ESA Hubble Space Telescope shows the tattered remnant of a supernova — a titanic explosion marking the end of the life of a dying star. This object — known as DEM L249 — is thought to have been created by a Type 1a supernova during the death throes of a white dwarf. While white dwarfs are usually stable, they can slowly accrue matter if they are part of a binary star system. This accretion of matter continues until the white dwarf reaches a critical mass and undergoes a catastrophic supernova explosion, ejecting a vast amount of material into space in the process. DEM L249 lies in the constellation Mensa and is within the Large Magellanic Cloud (LMC), a small satellite galaxy of the Milky Way only 160 000 light-years from Earth. The LMC is an ideal natural laboratory where astronomers can study the births, lives, and …

2 May 2022: The magnificent spiral galaxy M99 fills the frame in this image from the NASA/ESA Hubble Space Telescope. M99 — which lies roughly 42 million light-years from Earth in the constellation Coma Berenices — is a “grand design” spiral galaxy, so-called because of the well-defined, prominent spiral arms visible in this image. M99 was captured by Hubble’s Wide Field Camera 3 on two separate occasions, helping astronomers study two entirely different astronomical phenomena. The first set of observations aimed to explore a gap between two different varieties of cosmic explosions; novae and supernovae. Novae, which are caused by the interactions between white dwarfs and larger stars in binary systems, are far less bright than the supernovae which mark the catastrophically violent deaths of massive stars. However, current astronomical theories predict that sudden, fleeting events could occur that shine with brightnesses between those of novae and supernovae. Despite being described by astronomers …

25 April 2022: The ultra-diffuse galaxy GAMA 526784 appears as a tenuous patch of light in this image from the NASA/ESA Hubble Space Telescope. This wispy object resides in the constellation Hydra, roughly four billion light-years from Earth. Ultra-diffuse galaxies such as GAMA 526784 have a number of peculiarities. For example, their dark matter content can be either extremely low or extremely high — ultra-diffuse galaxies have been observed with an almost complete lack of dark matter, whereas others consist of almost nothing but dark matter. Another oddity of this class of galaxies is their anomalous abundance of bright globular clusters, something not observed in other types of galaxies. Hubble captured GAMA 526784 with the Advanced Camera for Surveys (ACS), which was installed in 2002 by astronauts during Hubble Servicing Mission 3B. Since then, the instrument has played a pivotal role in some of Hubble’s most impressive scientific results, including capturing the Hubble …

18 April 2022: Two merging galaxies in the VV689 system — nicknamed the Angel Wing —feature in this image from the NASA/ESA Hubble Space Telescope. Unlike chance alignments of galaxies which only appear to overlap as seen from our vantage point on Earth, the two galaxies in VV689 are in the midst of a collision. The galactic interaction has left the VV689 system almost completely symmetrical, giving the impression of a vast set of galactic wings. This angelic image comes from a set of Hubble observations inspecting the highlights of the Galaxy Zoo citizen science project. This crowdsourced astronomy project relied on hundreds of thousands of volunteers to classify galaxies and help astronomers wade through a deluge of data from robotic telescopes. In the process, volunteers discovered a rogues’ gallery of weird and wonderful galaxy types, some of which had not previously been studied. A similar, ongoing project called Radio Galaxy Zoo is …

11 April 2022: The spiral galaxy M91 fills the frame of this Wide Field Camera 3 observation from the NASA/ESA Hubble Space Telescope. M91 lies approximately 55 million light-years from Earth in the constellation Coma Berenices and — as is evident in this image — is a barred spiral galaxy. While M91’s prominent bar makes for a spectacular galactic portrait, it also hides an astronomical monstrosity. Like our own galaxy, M91 contains a supermassive black hole at its centre. A 2009 study using archival Hubble data found that this central black hole weighs somewhere between 9.6 and 38 million times as much as the Sun. Whilst archival Hubble data allowed astronomers to weigh M91’s central black hole, more recent observations have had other scientific aims. This observation is part of an effort to build a treasure trove of astronomical data exploring the connections between young stars and the clouds of cold gas in …

4 April 2022: The lazily winding spiral arms of the galaxy NGC 5921 snake across this image from the NASA/ESA Hubble Space Telescope. This galaxy lies approximately 80 million light-years from Earth, and much like our own galaxy, the Milky Way, contains a prominent bar. Roughly half of all spiral galaxies are thought to contain bars, and these bars affect their parent galaxies by fuelling star formation and affecting the motion of stars and interstellar gas. Appropriately, given NGC 5921’s serpentine spiral arms, this galaxy resides in the constellation Serpens in the northern celestial hemisphere. Serpens is the only one of the 88 modern constellations to consist of two unconnected regions — Serpens Caput and Serpens Cauda. These two regions — whose names mean the Serpent’s Head and the Serpent’s Tail, respectively — are separated by Ophiuchus, the Serpent Bearer. The scientific study behind this image was also split into two parts — …

28 March 2022: Tendrils of dark dust can be seen threading across the heart of the spiral galaxy NGC 7172 in this image from the NASA/ESA Hubble Space Telescope. The galaxy lies approximately 110 million light-years from Earth in the constellation Piscis Austrinus. The lane of dust threading its way across NGC 7172 — which is viewed side-on in this image — is obscuring the luminous heart of the galaxy, making NGC 7172 appear to be nothing more than a normal edge-on spiral galaxy. When astronomers inspected NGC 7172 across the electromagnetic spectrum they quickly discovered that there was more to it than meets the eye: NGC 7172 is a Seyfert galaxy — a type of galaxy with an intensely luminous active galactic nucleus powered by matter accreting onto a supermassive black hole. This image combines data from two sets of Hubble observations, both of which were proposed to study nearby active galactic …

21 March 2022: This cosmic portrait — captured with the NASA/ESA Hubble Space Telescope’s Wide Field Camera 3 — shows a stunning view of the spiral galaxy NGC 4571, which lies approximately 60 million light-years from Earth in the constellation Coma Berenices. This constellation — whose name translates as Bernice’s Hair — was named after an Egyptian queen who lived more than 2200 years ago. As majestic as spiral galaxies like NGC 4571 are, they are far from the largest structures known to astronomers. NGC 4571 is part of the Virgo cluster, which contains more than a thousand galaxies. This cluster is in turn part of the larger Virgo supercluster, which also encompasses the Local Group which contains our own galaxy, the Milky Way. Even larger than superclusters are galaxy filaments — the largest known structures in the Universe. This image comes from a large programme of observations designed to produce a treasure …

14 March 2022: This finely detailed image shows the heart of NGC 1097, a barred spiral galaxy that lies about 48 million light-years from Earth in the constellation Fornax. This picture reveals the intricacy of the web of stars and dust at NGC 1097’s centre, with the long tendrils of dust picked out in a dark red hue. The extent to which the galaxy’s structure is revealed is thanks to two instruments on the NASA/ESA Hubble Space Telescope: the Wide Field Camera 3 (WFC3) and the Advanced Camera for Surveys (ACS). The idea that a single image can be taken using two different cameras is not very intuitive. However, it makes far more sense after delving into how beautiful astronomical images like this one are composed. A helpful starting point is to consider what colour is, exactly. Our eyes can detect light waves at optical wavelengths between roughly 380 and 750 nanometres, using …

7 March 2022: An energetic outburst from an infant star streaks across this image from the NASA/ESA Hubble Space Telescope. This stellar tantrum — produced by an extremely young star in the earliest phase of formation — consists of an incandescent jet of gas travelling at supersonic speeds. As the jet collides with material surrounding the still-forming star, the shock heats this material and causes it to glow. The result is the colourfully wispy structures, which astronomers refer to as Herbig–Haro objects, billowing across the lower left of this image. Herbig–Haro objects are seen to evolve and change significantly over just a few years. This particular object, called HH34, was previously captured by Hubble between 1994 and 2007, and again in glorious detail in 2015. HH34 resides approximately 1250 light-years from Earth in the Orion Nebula, a large region of star formation visible to the unaided eye. The Orion Nebula is one of …

28 February 2022: The twin galaxies NGC 4496A and NGC 4496B dominate the frame in this image from the NASA/ESA Hubble Space Telescope. Both galaxies lie in the constellation Virgo, but despite appearing side-by-side in this image they are at vastly different distances from both Earth and one another. NGC 4496A is 47 million light-years from Earth while NGC 4496B is 212 million light-years away. The enormous distances between the two galaxies mean that the two cannot interact, and they only appear to overlap owing to a chance alignment. Chance galactic alignments such as this provide astronomers with the opportunity to delve into the distribution of dust in these galaxies. Galactic dust adds to the beauty of astronomical images — it can be seen in this image as the dark tendrils threading through both NGC 4496A and NGC 4496B — but it also complicates astronomers’ observations. Dust absorbs starlight, making stars seem dimmer …

21 February 2022: This striking image from the NASA/ESA Hubble Space Telescope showcases Arp 298, a stunning pair of interacting galaxies. Arp 298 — which comprises the two galaxies NGC 7469 and IC 5283 — lies roughly 200 million light-years from Earth in the constellation Pegasus. The larger of the two galaxies pictured here is the barred spiral galaxy NGC 7469, and IC 5283 is its diminutive companion. NGC 7469 is also host to an active, supermassive black hole and a bright ring of star clusters. The “Arp” in this galaxy pair’s name signifies that they are listed in the Atlas of Peculiar Galaxies compiled by the astronomer Halton Arp. The Atlas of Peculiar Galaxies is a rogues’ gallery of weird and wonderful galaxies containing peculiar structures, featuring galaxies exhibiting everything from segmented spiral arms to concentric rings. This interacting galaxy pair is a familiar sight for Hubble — a portrait of the …

14 February 2022: The mass of dust and bright swirls of stars in this image are the distant galaxy merger IC 2431, which lies 681 million light-years from Earth in the constellation Cancer. The NASA/ESA Hubble Space Telescope has captured what appears to be a triple galaxy merger in progress, as well as a tumultuous mixture of star formation and tidal distortions caused by the gravitational interactions of this galactic trio. The centre of this image is obscured by a thick cloud of dust — though light from a background galaxy can be seen piercing its outer extremities. This image is from a series of Hubble observations investigating weird and wonderful galaxies found by the Galaxy Zoo citizen science project. Using Hubble’s powerful Advanced Camera for Surveys (ACS), astronomers took a closer look at some of the more unusual galaxies that volunteers had identified. The original Galaxy Zoo project was the largest galaxy …

7 February 2022: It is now widely accepted amongst astronomers that an important aspect of how galaxies evolve is the way they interact with one another. Galaxies can merge, collide, or brush past one another — each of which has a significant impact on their shapes and structures. As common as these interactions are thought to be in the Universe, it is rare to capture an image of two galaxies interacting in such a visibly dynamic way. This image, from the NASA/ESA Hubble Space Telescope, feels incredibly three-dimensional for a piece of deep-space imagery. The subject of this image is named Arp 282, an interacting galaxy pair that is composed of the Seyfert galaxy NGC 169 (bottom) and the galaxy IC 1559 (top). If you’re interested in learning more about Seyfert galaxies, you can read about the Seyfert galaxy NGC 5728 here. Interestingly, both of the galaxies comprising Arp 282 have monumentally energetic …

31 January 2022: The dwarf galaxy NGC 1705 is featured in this image from the NASA/ESA Hubble Space Telescope. This diminutive galaxy lies in the southern constellation Pictor, and is approximately 17 million light-years from Earth. NGC 1705 is a cosmic oddball — it is small, irregularly shaped, and has recently undergone a spate of star formation known as a starburst. Despite these eccentricities, NGC 1705 and other dwarf irregular galaxies like it can provide valuable insights into the overall evolution of galaxies. Dwarf irregular galaxies tend to contain few elements other than hydrogen or helium, and are considered to be similar to the earliest galaxies that populated the Universe. The data shown in this image come from a series of observations designed to unveil the interplay between stars, star clusters, and ionised gas in nearby star-forming galaxies. By observing a specific wavelength of light known as H-alpha with Hubble’s Wide Field Camera …

24 January 2022: The subject of this image is a group of three galaxies, collectively known as NGC 7764A. They were imaged by the NASA/ESA Hubble Space Telescope, using both its Advanced Camera for Surveys (ACS) and Wide Field Camera 3 (WFC3). The two galaxies in the upper right of the image appear to be interacting with one another — indeed, the long trails of stars and gas extending from them both give the impression that they have both just been struck at great speed, thrown into disarray by the bowling-ball-shaped galaxy to the lower left of the image. In reality, however, interactions between galaxies happen over very long time periods, and galaxies rarely collide head-on with one another. It is also unclear whether the galaxy to the lower left is actually interacting with the other two, although they are so relatively close in space that it seems possible that they are. By …

17 January 2022: The spiral arms of the galaxy NGC 3318 are lazily draped across this image from the NASA/ESA Hubble Space Telescope. This spiral galaxy lies in the constellation Vela and is roughly 115 million light-years away from Earth. Vela was originally part of a far larger constellation, known as Argo Navis after the fabled ship Argo from Greek mythology, but this unwieldy constellation proved to be impractically large. Argo Navis was split into three separate parts called Carina, Puppis, and Vela — each named after part of the Argo. As befits a galaxy in a nautically inspired constellation, the outer edges of NGC 3318 almost resemble a ship’s sails billowing in a gentle breeze.

10 January 2022: The lazily winding spiral arms of the spectacular galaxy NGC 976 fill the frame of this image from the NASA/ESA Hubble Space Telescope. This spiral galaxy lies around 150 million light-years from the Milky Way in the constellation Aries. Despite its tranquil appearance, NGC 976 has played host to one of the most violent astronomical phenomena known — a supernova explosion. These cataclysmicly violent events take place at the end of the lives of massive stars, and can outshine entire galaxies for a short period. While supernovae mark the deaths of massive stars, they are also responsible for the creation of heavy elements that are incorporated into later generations of stars and planets. Supernovae are also a useful aid for astronomers who measure the distances to faraway galaxies. The amount of energy thrown out into space by supernova explosions is very uniform, allowing astronomers to estimate their distances from how …

3 January 2022: This image from the NASA/ESA Hubble Space Telescope captures the spiral galaxy NGC 105, which lies roughly 215 million light-years away in the constellation Pisces. While it looks like NGC 105 is plunging edge-on into a collision with a neighbouring galaxy, this is just the result of the chance alignment of the two objects in the night sky. NGC 105’s elongated neighbour is actually far more distant and remains relatively unknown to astronomers. These misleading conjunctions occur frequently in astronomy — for example, the stars in constellations are at vastly different distances from Earth, and only appear to form patterns thanks to the chance alignment of their component stars. The Wide Field Camera 3 observations in this image are from a vast collection of Hubble measurements examining nearby galaxies which contain two fascinating astronomical phenomena — Cepheid variables and cataclysmic supernova explosions. Whilst these two phenomena may appear to be …

27 December 2021: The lonely spiral galaxy UGC 9391 is shown in this image from the NASA/ESA Hubble Space Telescope’s Wide Field Camera 3. This galaxy resides 130 million light-years from Earth in the constellation Draco near the north celestial pole. The star-studded spiral arms stand in splendid isolation against a backdrop of distant galaxies, which are only visible as indistinct swirls or smudges thanks to their vast distances from Earth. The image also features some much brighter foreground stars closer to home. These bright nearby stars are ringed with diffraction spikes — prominent spikes caused by light interacting with the inner workings of Hubble’s complicated optics. This image is from a set of Hubble observations which astronomers used to construct the “Cosmic Distance Ladder” — a set of connected measurements allowing the distances to the most distant astronomical objects to be determined. Astronomical distances are only directly measurable for relatively nearby objects …

20 December 2021: The open star cluster NGC 1755 resembles a pinch of salt strewn on a jet-black tablecloth in this image from the NASA/ESA Hubble Space Telescope. This collection of stars resides in one the Milky Way’s near neighbours — the Large Magellanic Cloud — and measures 120 light-years from side to side. Despite this impressive breadth, NGC 1755 is a member of the smaller class of star clusters. Star clusters are gravitationally bound collections of stars, and come in two main varieties — smaller open clusters like NGC 1755, which are hosts to younger stars, and gargantuan globular clusters, which can contain millions of older stars. Hubble gazed into the heart of NGC 1755 in order to better understand how different populations of stars can co-exist in a single cluster. A population of stars is a group of stars with similar properties such as age or chemical composition, and these populations …

13 December 2021: In this image, the NASA/ESA Hubble Space Telescope captures a side-on view of NGC 3568, a barred spiral galaxy roughly 57 million light-years from the Milky Way in the constellation Centaurus. In 2014 the light from a supernova explosion in NGC 3568 reached Earth — a sudden flare of light caused by the titanic explosion accompanying the death of a massive star. Whilst most astronomical discoveries are the work of teams of professional astronomers, this supernova was discovered by amateur astronomers from the Backyard Observatory Supernova Search in New Zealand. Dedicated amateur astronomers often make intriguing discoveries — particularly of fleeting astronomical phenomena such as supernovae. This Hubble observation comes from a hoard of data built up to pave the way for future science with the upcoming NASA/ESA/CSA James Webb Space Telescope. By combining ground-based observations with data from Hubble’s Advanced Camera for Surveys and Wide Field Camera 3, astronomers …

6 December 2021: This stellar whirlpool is a spiral galaxy named NCG 7329, which has been imaged by Hubble’s Wide Field Camera 3 (WFC3). Creating a colourful image such as this one using a telescope such as Hubble is not as straightforward as pointing and clicking a camera. Commercial cameras will typically try to collect as much light of all visible wavelengths as they can, in order to create the most vibrant images possible. In contrast, raw images collected by Hubble are always monochromatic, because astronomers typically want to capture very specific ranges of wavelengths of light at any time, in order to do the best, most accurate science possible. In order to control which wavelengths of light will be collected, Hubble’s cameras are equipped with a wide variety of filters, which only allow certain wavelengths of light to reach the cameras’ CCDs (a CCD is a camera’s light sensor — phone cameras …

29 November 2021: In this image the NASA/ESA Hubble Space Telescope peers into the spiral galaxy NGC 1317 in the constellation Fornax, more than 50 million light-years from Earth. This galaxy is one of a pair, but NGC 1317’s rowdy larger neighbour NGC 1316 lies outside Hubble’s field of view. Despite the absence here of its neighbouring galaxy, NGC 1317 is accompanied in this image by two objects from very different parts of the Universe. The bright point ringed with a criss-cross pattern is a star from our own galaxy surrounded by diffraction spikes, whereas the redder elongated smudge is a distant galaxy lying far beyond NGC 1317. The data presented in this image are from a vast observing campaign of hundreds of observations from Hubble’s Wide Field Camera 3 and Advanced Camera for Surveys. Combined with data from the ALMA array in the Atacama desert, these observations help astronomers chart the connections …

22 November 2021: This star- and galaxy-studded image was captured by Hubble’s Wide Field Camera 3 (WFC3), using data that were collected for scientific purposes. The object of interest was a galaxy that is visible in the bottom right corner of the image, named SGAS 0033+02. What makes this particular galaxy interesting is a little unusual — it appears not just once in this image, but three times. The thrice-visible galaxy is a little difficult to spot: it appears once as a curved arc and twice more as small round dots around the star. SGAS 0033+02’s multiple appearances in the same image are not the result of an error, but instead are due to a remarkable phenomenon known as gravitational lensing. Gravitational lensing occurs when the light from a very distant galaxy — such as SGAS 0033+02 — is curved (or ‘lensed’) by the gravity of a massive celestial object that lies in …

15 November 2021: This astronomical portrait from the NASA/ESA Hubble Space Telescope showcases an edge-on view of the majestic spiral galaxy UGC 11537. Hubble’s Wide Field Camera 3 has captured the tightly wound spiral arms swirling around the heart of UGC 11537 at infrared and visible wavelengths, showing both the bright bands of stars and the dark clouds of dust threading throughout the galaxy. UGC 11537 is 230 million light-years away in the constellation Aquila, and lies close to the plane of the Milky Way. Being so close to the starry band of the Milky Way means that foreground stars from our own galaxy have crept into the image — the two prominent stars in front of UGC 11537 are interlopers from within the Milky Way. These bright foreground stars are surrounded by diffraction spikes — imaging artifacts caused by starlight interacting with Hubble’s inner structure. This image came from a set of …

8 November 2021: This image from the NASA/ESA Hubble Space Telescope features the spiral galaxy Mrk 1337, which is roughly 120 million light-years away from Earth in the constellation Virgo. Hubble’s Wide Field Camera 3 snapped Mrk 1337 at a wide range of ultraviolet, visible and infrared wavelengths, producing this richly detailed image. Mrk 1337 is a weakly barred spiral galaxy, which as the name suggests means that the spiral arms radiate from a central bar of gas and stars. Bars occur in roughly half of spiral galaxies, including our own galaxy the Milky Way. These observations are part of a campaign to improve our knowledge of how fast the universe is expanding. They were proposed by Adam Riess, who was awarded a Nobel Laureate in physics 2011 for his contributions to the discovery of the accelerating expansion of the Universe, alongside Saul Perlmutter and Brian Schmidt. Links Video of Cosmological Curiosity

1 November 2021: This NASA/ESA Hubble Space Telescope Picture of the Week features the galaxy NGC 6984, an elegant spiral galaxy in the constellation Indus roughly 200 million light-years away from Earth. The galaxy is a familiar sight for Hubble, having already been captured in 2013. The sweeping spiral arms are threaded through with a delicate tracery of dark lanes of gas and dust, and studded with bright stars and luminous star-forming regions. These new observations were made following an extremely rare astronomical event — a double supernova in NGC 6984. Supernovae are unimaginably violent explosions on a truly vast scale, precipitated by the deaths of massive stars. These events are powerful but rare and fleeting — a single supernova can outshine its host galaxy for a brief time. The discovery of two supernovae at virtually the same time and location (in astronomical terms) prompted speculation from astronomers that the two supernovae may …

25 October 2021: This jewel-bright Picture of the Week features the spiral galaxy NGC 2903. This image was captured using Hubble’s Advanced Camera for Surveys (ACS) and Wide Field Camera 3 (WFC3), which were installed on Hubble in 2002 and 2009 respectively. Interestingly, Hubble has observed this particular galaxy before, in 2001, when neither the ACS or the WFC3 had yet been installed. The 2021 image boasts higher resolution, which means that NGC 2903 is more finely detailed than in the 2001 image. The ACS and WFC2 collectively cover a wide range of ultraviolet, optical and infrared wavelengths, which means that the 2021 image also has superior wavelength coverage to that of its 20-year-old predecessor. The 2001 image was taken using the Wide Field Planetary Camera 2 (WFPC2), which was Hubble’s workhorse instrument from 1993 until 2009 when it was replaced by the WFC3. Hubble has a long and fascinating history of crewed …

18 October 2021: This observation from the NASA/ESA Hubble Space Telescope showcases Arp 86, a peculiar pair of interacting galaxies which lies roughly 220 million light-years from Earth in the constellation Pegasus. Arp 86 is composed of the two galaxies NGC 7752 and NGC 7753 — NGC 7753 is the large spiral galaxy dominating this image, and NGC 7752 is its smaller companion. The diminutive companion galaxy almost appears to be attached to NGC 7753, and it is this peculiarity that has earned the designation “Arp 86” — signifying that the galaxy pair appears in the Atlas of Peculiar Galaxies compiled by the astronomer Halton Arp in 1966. The gravitational squabble between the two galaxies is doomed to end catastrophically for NGC 7752. It will eventually either be flung out into intergalactic space or be entirely engulfed by its far larger neighbour. Hubble observed Arp 86 as part of a larger effort to …

11 October 2021: NGC 4666 takes centre stage in this image from the NASA/ESA Hubble Space Telescope. This majestic spiral galaxy lies about 80 million light-years away in the constellation Virgo, and is undergoing a particularly intense episode of star formation. Astronomers refer to galaxies which are forming stars anomalously quickly as starburst galaxies. NGC 4666’s starburst is thought to be due to gravitational interactions with its unruly neighbours — including the nearby galaxy NGC 4668 and a dwarf galaxy. NGC 4666’s burst of star formation is driving an unusual form of extreme galactic weather known as a superwind — a gigantic transfer of gas from the bright central heart of the galaxy out into space. This superwind is the result of driving winds from short-lived massive stars formed during NGC 4666’s starburst as well as spectacularly energetic supernova explosions. Two such supernova explosions have been seen in NGC 4666 within the last …

4 October 2021: This Picture of the Week features two interacting galaxies that are so intertwined, they have a collective name — Arp 91. This delicate galactic dance is taking place over 100 million light-years from Earth, and was captured by the NASA/ESA Hubble Space Telescope. The two galaxies comprising Arp 91 do have their own names: the lower galaxy, which in this image looks like a bright spot, is known as NGC 5953; and the ovoid galaxy to the upper right is NGC 5954. In reality, both of these galaxies are spiral galaxies, but their shapes appear very different because they are orientated differently with respect to Earth. Arp 91 provides a particularly vivid example of galactic interaction. NGC 5954 is clearly being tugged towards NGC 5953 — it looks like it is extending one spiral arm downwards. It is the immense gravitational attraction of the two galaxies that is causing them …

27 September 2021: Meet NGC 5728, a spiral galaxy around 130 million light-years from Earth. This image was captured using Hubble’s Wide Field Camera 3 (WFC3), which is extremely sensitive to visible and infrared light. Therefore, this image beautifully captures the regions of NGC 5728 that are emitting visible and infrared light. However, there are many other types of light that galaxies such as NGC 5728 can emit, which WFC3 cannot see. In this image, NCG 5728 appears to be an elegant, luminous, barred spiral galaxy. What this image does not show, however, is that NGC 5728 is also a monumentally energetic type of galaxy, known as a Seyfert galaxy. This extremely energetic class of galaxies are powered by their active cores, which are known as active galactic nuclei (AGNs). There are many different types of AGNs, and only some of them power Seyfert galaxies. NGC 5728, like all Seyfert galaxies, is distinguished …

20 September 2021: This sparkling starfield, captured by the NASA/ESA Hubble Space Telescope’s Wide Field Camera 3 and Advanced Camera for Surveys, contains the globular cluster ESO 520-21 (also known as Palomar 6). A densely packed, roughly spherical collection of stars, it lies close to the centre of the Milky Way, where interstellar gas and dust absorb starlight and make observations more challenging. This absorption by interstellar material affects some wavelengths of light more than others, changing the colours of astronomical objects and causing them to appear redder than they actually are. Astronomers call this process “reddening”, and it makes determining the properties of globular clusters close to the galactic centre — such as ESO 520-21 — particularly difficult. ESO 520-21 lies in the constellation Ophiuchus, near the celestial equator. Ophiuchus was one of the 48 constellations which appeared in the writings of the second-century Egyptian astronomer Ptolemy, all of which are among …

13 September 2021: This comparison view shows puffing dust bubbles and an erupting gas shell — the final acts of a monster star.You can explore the detail of the nebula surrounding the star AG Carinae by using the slider tool on the image above. This Picture of the Week showcases new views of the dual nature of the star AG Carinae, which was the target of the NASA/ESA Hubble Space Telescope’s 31st anniversary image in April 2021. This new perspective was developed thanks to Hubble’s observations of the star in 2020 and 2014, along with others captured by the telescope’s WFPC2 instrument in 1994. The first image showcases the details of the ionised hydrogen and ionised nitrogen emissions from the nebula (seen here in red). In the second image, the blue demonstrates the contrasting appearance of the distribution of the dust that shines of reflected stellar light. Astronomers believe that the dust bubbles …

6 September 2021: This star-studded image from the NASA/ESA Hubble Space Telescope depicts NGC 6717, which lies more than 20 000 light-years from Earth in the constellation Sagittarius. NGC 6717 is a globular cluster, a roughly spherical collection of stars tightly bound together by gravity. Globular clusters contain more stars in their centres than their outer fringes, as this image aptly demonstrates; the sparsely populated edges of NGC 6717 are in stark contrast to the sparkling collection of stars at its centre. The centre of the image also contains some interlopers from closer to home. Bright foreground stars close to Earth are surrounded by criss-cross diffraction spikes formed by starlight interacting with the structures supporting Hubble’s secondary mirror. The area of the night sky which contains the constellation Sagittarius also contains the centre of the Milky Way, which is filled with light-absorbing gas and dust. This absorption of light — which astronomers refer …

30 August 2021: This striking image features a relatively rare celestial phenomenon known as a Herbig–Haro object. This particular Herbig–Haro object is named HH111, and was imaged by Hubble’s Wide Field Camera 3 (WFC3). These spectacular objects are formed under very specific circumstances. Newly formed stars are often very active, and in some cases they expel very narrow jets of rapidly moving ionised gas — gas that is so hot that its molecules and atoms have lost their electrons, making the gas highly charged. The streams of ionised gas then collide with the clouds of gas and dust surrounding newly-formed stars at speeds of hundreds of kilometres per second. It is these energetic collisions that create Herbig–Haro objects such as HH111. WFC3 takes images at optical and infrared wavelengths, which means that it observes objects at a wavelength range similar to the range that human eyes are sensitive to (optical) and a range …

23 August 2021: This Picture of the Week shows an open cluster known as NGC 2164, which was first discovered in 1826 by a Scottish astronomer named James Dunlop. NGC 2164 is located within one of the Milky Way galaxy's closest neighbours — the satellite galaxy known as the Large Magellanic Cloud. The Large Magellanic cloud is a relatively small galaxy that lies about 160 000 light-years from Earth. It is considered a satellite galaxy because it is gravitationally bound to the Milky Way. In fact, the Large Magellanic cloud is on a very slow collision course with the Milky Way — it’s predicted that they will collide 2.4 billion years from now. The Large Magellanic Cloud only contains about one hundredth as much mass as the Milky Way, but it still contains billions of stars. The open cluster NGC 2164 is in good company in the Large Magellanic Cloud — the satellite …

16 August 2021: This jewel-bright image from the NASA/ESA Hubble Space Telescope shows NGC 1385, a spiral galaxy 30 million light-years away from Earth, which lies in the constellation Fornax. The image was taken with Hubble’s Wide Field Camera 3 (WFC3), which is often referred to as Hubble’s workhorse camera, thanks to its reliability and versatility. It was installed in 2009 when astronauts last visited Hubble, and 12 years later it remains remarkably productive. NGC 1385’s home — the Fornax constellation — is not named after an animal or an ancient God, as are many of the other constellations. Fornax is simply the Latin word for a furnace. The constellation was named Fornax by Nicolas-Louis de Lacaille, a French astronomer who was born in 1713. Lacaiile named 14 of the 88 constellations that are still recognised today. He seems to have had a penchant for naming constellations after scientific instruments, including Atlia (the …

9 August 2021: Clustered at the centre of this image are six luminous spots of light, four of them forming a circle around a central pair. Appearances can be deceiving, however, as this formation is not composed of six individual galaxies, but only three: to be precise, a pair of galaxies and one distant quasar. Hubble data also indicates that there is a seventh spot of light in the very center, which is a rare fifth image of the distant quasar. This rare phenomenon is caused by the presence of two galaxies in the foreground that act as a lens. These galaxies were imaged in spectacular detail by Hubble’s Wide Field Camera 3 (WFC3), which was installed on Hubble in 2009 during Hubble Servicing Mission 4, Hubble’s final servicing mission. The WFC3 was intended to operate until 2014, but 12 years after it was installed it continues to provide both top-quality data and …

2 August 2021: The spiral galaxy IC 1954 takes centre stage in this image from the NASA/ESA Hubble Space Telescope. The galaxy, which lies approximately 45 million light-years from Earth in the constellation Horologium (The Clock), boasts a bright central bar and lazily winding spiral arms threaded with dark clouds of dust. This portrait of IC 1954 was captured with Hubble’s Wide Field Camera 3, and is one of a set of observations designed to take advantage of some telescope teamwork. Hubble observed groups of young stars in nearby galaxies at ultraviolet and optical wavelengths while the Atacama Large Millimeter/submillimeter Array — a ground-based radio telescope — gathered data on star-forming discs and clouds of cold gas. Combining the two sets of observations allowed astronomers to join the dots and understand the connections between young stars and the clouds of cold gas which give rise to them. These observations also lay the groundwork …

26 July 2021: A dramatic triplet of galaxies takes centre stage in this latest Picture of the Week from the NASA/ESA Hubble Space Telescope, which captures a three-way gravitational tug-of-war between interacting galaxies. This system —known as Arp 195— is featured in the Atlas of Peculiar Galaxies, a list which showcases some of the weirder and more wonderful galaxies in the universe. Observing time with the Hubble Space Telescope is extremely valuable, so astronomers don't want to waste a second. The schedule for Hubble observations is calculated using a computer algorithm which allows the spacecraft to occasionally gather bonus snapshots of data between longer observations. This image of the clashing triplet of galaxies in Arp 195 is one such snapshot. Extra observations such as these do more than provide spectacular images — they also help to identify promising targets to follow up with telescopes such as the upcoming NASA/ESA/CSA James Webb Space Telescope. …

19 July 2021: The centre of this image from the NASA/ESA Hubble Space Telescope is framed by the tell-tale arcs that result from strong gravitational lensing, a striking astronomical phenomenon which can warp, magnify, or even duplicate the appearance of distant galaxies. Gravitational lensing occurs when light from a distant galaxy is subtly distorted by the gravitational pull of an intervening astronomical object. In this case, the relatively nearby galaxy cluster MACSJ0138.0-2155 has lensed a significantly more distant quiescent galaxy — a slumbering giant known as MRG-M0138 which has run out of the gas required to form new stars and is located 10 billion light years away. Astronomers can use gravitational lensing as a natural magnifying glass, allowing them to inspect objects like distant quiescent galaxies which would usually be too difficult for even Hubble to resolve. This image was made using observations from eight different infrared filters spread across two of Hubble’s …

12 July 2021: This image shows the globular cluster NGC 6380, which lies around 35 000 light-years from Earth, in the constellation Scorpio (The Scorpion). The very bright star at the top of the image is HD 159073, which is only around 4000 light-years from Earth, making it a much nearer neighbour to Earth than NGC 6380. This image was taken with Hubble’s Wide Field Camera 3 (WFC3), which, as its name suggests, has a wide field of view, meaning that it can image relatively large areas of the sky in enormous detail. NGC 6380 is not a particularly exciting name, but it indicates that this cluster is catalogued in the New General Catalogue (NGC), which was originally compiled in 1888. This cluster has, however, been known by many other names. It was originally discovered by James Dunlop in 1826, and he rather immodestly named it Dun 538. Eight years later, in 1834, …

5 July 2021: Two things capture your attention in this spectacular Picture of the Week, which was taken using Hubble’s Wide Field Camera 3 (WFC3): the two enormous galaxies that flank the left and right sides of the image. The galaxy on the left is a lenticular galaxy, which rejoices in the name of 2MASX J03193743+4137580. The side-on spiral galaxy on the right is more simply named UGC 2665. Both galaxies lie approximately 350 million light-years from Earth, and they both form part of the enormous Perseus galaxy cluster. Perseus is an important figure in Greek mythology, renowned for slaying Medusa the Gorgon — who is herself famous for the unhappy reason that she was cursed to have living snakes for hair. Given Perseus’s impressive credentials, it seems appropriate that the eponymous galaxy cluster is one of the biggest objects in the known Universe, consisting of thousands of galaxies, only a few of …

28 June 2021: This Picture of the Week depicts the open star cluster NGC 330, which lies around 180,000 light-years away inside the Small Magellanic Cloud. The cluster — which is in the constellation Tucana (The Toucan) — contains a multitude of stars, many of which are scattered across this striking image. The most stunning object in this image is actually the very small star cluster in the lower left corner of the image, surrounded by a nebula of ionised hydrogen (red) and dust (blue). Named GALFOR 1, the cluster was discovered in 2018 in Hubble's archival data, which was used to create this latest image from Hubble. To better understand this star cluster, specifically whether the nebula surrounding the cluster also contains a bow shock, scientists will need high resolution infrared imagery from the upcoming NASA/ESA/CSA James Webb Space Telescope. This image also contains clues about the inner workings of Hubble itself. …

21 June 2021: A cataclysmic cosmic collision takes centre stage in this Picture of the Week. The image features the interacting galaxy pair IC 1623, which lies around 275 million light-years away in the constellation Cetus (The Whale). The two galaxies are in the final stages of merging, and astronomers expect a powerful inflow of gas to ignite a frenzied burst of star formation in the resulting compact starburst galaxy. This interacting pair of galaxies is a familiar sight; Hubble captured IC 1623 in 2008 using two filters at optical and infrared wavelengths using the Advanced Camera for Surveys. This new image incorporates new data from Wide Field Camera 3, and combines observations taken in eight filters spanning infrared to ultraviolet wavelengths to reveal the finer details of IC 1623. Future observations of the galaxy pair with the NASA/ESA/CASA James Webb Space Telescope will shed more light on the processes powering extreme star …