Picture of the Week

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 …

14 June 2021: This image shows the spiral galaxy NGC 3254, observed using Hubble's Wide Field Camera 3 (WFC3). WFC3 has the capacity to observe ultraviolet, visible and near-infrared light, and this image is a composite of observations taken in the visible and infrared. In this image, NGC 3254 looks like a typical spiral galaxy, viewed side-on. However, NGC 3254 has a fascinating secret that it is hiding in plain sight — it is a Seyfert galaxy, meaning that it has an extraordinarily active core, known as an active galactic nucleus, which releases as much energy as the rest of the galaxy put together. Seyfert galaxies are not rare — about 10% of all galaxies are thought to be Seyfert galaxies. They belong to the class of “active galaxies” — galaxies that have supermassive black holes at their centres that are actively accreting material, which releases vast amounts of radiation as it is …

7 June 2021: This image, taken with Hubble’s Wide Field Camera 3 (WFC3), features the spiral galaxy NGC 4680. At 2 o’clock and 7 o’clock two other galaxies can be seen flanking NGC 4680. NGC 4680 enjoyed a wave of attention in 1997, as it played host to a supernova explosion known as SN 1997bp. Amazingly, the supernova was identified by an Australian amateur astronomer named Robert Evans, who has identified an extraordinary 42 supernova explosions. NGC 4680 is actually a rather tricky galaxy to classify. It is sometimes referred to as a spiral galaxy, but it is also sometimes classified as a lenticular galaxy. Lenticular galaxies fall somewhere in between spiral galaxies and elliptical galaxies. Whilst NGC 4680 does have distinguishable spiral arms, they are not clearly defined, and the tip of one arm appears very diffuse. Galaxies are not static, and their morphologies (and therefore their classifications) vary throughout their lifetimes. …

31 May 2021: This image features the spiral galaxy NGC 691, imaged in fantastic detail by Hubble’s Wide Field Camera 3 (WFC3). This galaxy is the eponymous member of the NGC 691 galaxy group, a group of gravitationally bound galaxies that lie about 120 million light-years from Earth. Objects such as NGC 691 are observed by Hubble using a range of filters. Each filter only allows certain wavelengths of light to reach Hubble’s WFC3. The images collected using different filters are then coloured by specialised visual artists who can make informed choices about which colour best corresponds to which filter. By combining the coloured images from individual filters, a full-colour image of the astronomical object can be recreated. In this way, we can get remarkably good insight into the nature and appearance of these objects. Links Video of the Eponymous NGC 691

24 May 2021: This image shows the spiral galaxy NGC 5037, which is found in the constellation of Virgo and was first documented by William Herschel in 1785. It lies about 150 million light-years away from Earth, and yet it is possible to see the delicate structures of gas and dust within the galaxy in extraordinary detail. This was made possible by Hubble’s Wide Field Camera 3 (WFC3), which was used to collect the exposures that were combined to create this image. WFC3 is a very versatile camera, as it can collect ultraviolet, visible and infrared light, thereby providing a wealth of information about the objects that it observes. WFC3 was installed on Hubble by astronauts in 2009, during servicing mission 4, which was Hubble’s fifth and final servicing mission. Servicing mission 4 was intended to prolong Hubble’s life for another five years. 12 years later, both Hubble and WFC3 remain in active …

17 May 2021: This packed ESA/Hubble Picture of the Week showcases the galaxy cluster ACO S 295, as well as a jostling crowd of background galaxies and foreground stars. Galaxies of all shapes and sizes populate this image, ranging from stately spirals to fuzzy ellipticals. As well as a range of sizes, this galactic menagerie boasts a range of orientations, with spiral galaxies such as the one at the centre of this image appearing almost face on, and some edge-on spiral galaxies visible only as thin slivers of light. The cluster dominates the centre of this image, both visually and physically. The huge mass of the galaxy cluster has gravitationally lensed the background galaxies, distorting and smearing their shapes. As well as providing astronomers with a natural magnifying glass with which to study distant galaxies, gravitational lensing has subtly framed the centre of this image, producing a visually striking scene. Links Video of …

10 May 2021: This Picture of the Week showcases the emission nebula NGC 2313. The bright star V565 — surrounded by four prominent diffraction spikes — illuminates a silvery, fan-shaped veil of gas and dust, while the right half of this image is obscured by a dense cloud of dust. Nebulae with similar shapes — a star accompanied by a bright fan of gas — were once referred to as cometary nebulae, though the name is no longer used. The language that astronomers use changes as we become better acquainted with the Universe, and astronomical history is littered with now-obsolete phrases to describe objects in the night sky, such as “spiral nebulae” for spiral galaxies or “inferior planets” for Mercury and Venus.

3 May 2021: This detailed image features Abell 3827, a galaxy cluster that offers a wealth of exciting possibilities for study. It was observed by Hubble in order to study dark matter, which is one of the greatest puzzles cosmologists face today. The science team used Hubble’s Advanced Camera for Surveys (ACS) and Wide Field Camera 3 (WFC3) to complete their observations. The two cameras have different specifications and can observe different parts of the electromagnetic spectrum, so using them both allowed the astronomers to collect more complete information. Abell 3827 has also been observed previously by Hubble, because of the interesting gravitational lens at its core. Looking at this cluster of hundreds of galaxies, it is amazing to recall that until less than 100 years ago, many astronomers believed that the Milky Way was the only galaxy in the Universe. The possibility of other galaxies had been debated previously, but the matter …

26 April 2021: The interaction of two doomed stars has created this spectacular ring adorned with bright clumps of gas — a diamond necklace of cosmic proportions. Fittingly known as the Necklace Nebula, this planetary nebula is located 15 000 light-years away from Earth in the small, dim constellation of Sagitta (The Arrow). The Necklace Nebula — which also goes by the less glamorous name of PN G054.2-03.4 — was produced by a pair of tightly orbiting Sun-like stars. Roughly 25 000 years ago, one of the aging stars expanded and engulfed its smaller companion, creating something astronomers call a “common envelope”. The smaller star continued to orbit inside its larger companion, increasing the bloated giant’s rotation rate until large parts of it spun outwards into space. This escaping ring of debris formed the Necklace Nebula, with particularly dense clumps of gas forming the bright “diamonds” around the ring. The pair of stars …

19 April 2021: This image shows a close-up portrait of the magnificent spiral galaxy NGC 4603, which lies over 100 million light-years away in the constellation of Centaurus (The Centaur). Bright bands of blue young stars make up the arms of this galaxy, which wind lazily outwards from the luminous core. The intricate red-brown filaments threading through the spiral arms are known as dust lanes, and consist of dense clouds of dust which obscure the diffuse starlight from the galaxy. This galaxy is a familiar subject for Hubble. In the last years of the twentieth century, NGC 4603 was keenly and closely watched for signs of a peculiar class of stars known as Cepheid variables. These stars have a luminosity closely tied to the period with which they darken and brighten, allowing astronomers to accurately measure how far they are from Earth. Distance measurements from Cepheid variables are key to measuring the furthest …

12 April 2021: This extraordinary image from the NASA/ESA Hubble Space Telescope of the galaxy cluster Abell 2813 (also known as ACO 2813) has an almost delicate beauty, which also illustrates the remarkable physics at work within it. The image spectacularly demonstrates the concept of gravitational lensing. In amongst the tiny dots, spirals and ovals that are the galaxies that belong to the cluster, there are several distinct crescent shapes. These curved arcs of light are strong examples of a phenomenon known as gravitational lensing. The image was compiled using observations taken with the Hubble Space Telescope’s Advanced Camera for Surveys (ACS) and Wide Field Camera 3 (WFC3). Gravitational lensing occurs when an object’s mass causes light to bend. The curved crescents and s-shapes of light in this image are not curved galaxies, but are light from galaxies that actually lie beyond Abell 2813. The galaxy cluster has so much mass that it …

5 April 2021: The luminous heart of the galaxy M61 dominates this image, framed by its winding spiral arms threaded with dark tendrils of dust. As well as the usual bright bands of stars, the spiral arms of M61 are studded with ruby-red patches of light. Tell-tale signs of recent star formation, these glowing regions lead to M61’s classification as a starburst galaxy. Though the gleaming spiral of this galaxy makes for a spectacular sight, one of the most interesting features of M61 lurks unseen at the centre of this image. As well as widespread pockets of star formation, M61 hosts a supermassive black hole more than 5 million times as massive as the Sun. M61 appears almost face-on, making it a popular subject for astronomical images, even though the galaxy lies more than 52 million light-years from Earth. This particular astronomical image incorporates data from not only Hubble, but also the FORS …

29 March 2021: This Picture of the Week revisits the Veil Nebula, a popular subject for Hubble images! This object was featured in a previous Hubble photo release, but now new processing techniques have been applied, bringing out fine details of the nebula’s delicate threads and filaments of ionised gas. To create this colourful image, observations taken by Hubble's Wide Field Camera 3 instrument through 5 different filters were used. The new post-processing methods have further enhanced details of emissions from doubly ionised oxygen (seen here in blues), ionised hydrogen and ionised nitrogen (seen here in reds). The Veil Nebula lies around 2100 light-years from Earth in the constellation of Cygnus (The Swan), making it a relatively close neighbour in astronomical terms. Only a small portion of the nebula was captured in this image. The Veil Nebula is the visible portion of the nearby Cygnus Loop, a supernova remnant formed roughly 10 000 …

22 March 2021: This week’s Hubble/ESA Picture of the Week features NGC 7678 — a galaxy located approximately 164 million light-years away in the constellation of Pegasus (The Winged Horse). With a diameter of around 115 000 light-years, this bright spiral galaxy is a similar size to our own galaxy (the Milky Way), and was discovered in 1784 by the German-British astronomer William Herschel. The Atlas of Peculiar Galaxies is a catalogue which was produced in 1966 by the American astronomer Halton Arp. NGC 7678 is among the 338 galaxies presented in this catalogue, which organises peculiar galaxies according to their unusual features. Catalogued here as Arp 28, this galaxy is listed together with six others in the group “spiral galaxies with one heavy arm”.