Picture of the Week

2 December 2024: The subject of this NASA/ESA Hubble Space Telescope Picture of the Week is NGC 1637, a spiral galaxy located 38 million light-years from Earth in the constellation Eridanus. This image comes from an observing programme dedicated to studying star formation in nearby galaxies. Stars form in cold, dusty gas clouds that collapse under their own gravity. As young stars grow, they heat their nurseries through starlight, winds, and powerful outflows. Together, these factors play a role in controlling the rate at which future generations of stars form. Evidence of star formation is scattered all around NGC 1637, if you know where to look. The galaxy’s spiral arms are dotted with what appear to be pink clouds, many of which are accompanied by bright blue stars. The pinkish colour comes from hydrogen atoms that have been excited by ultraviolet light from young, massive stars. This contrasts with the warm yellow glow …

25 November 2024: Featured in this new NASA/ESA Hubble Space Telescope Picture of the Week is the spiral galaxy NGC 2090, located in the constellation Columba. This galaxy is notable as a part of the group of galaxies studied in Hubble’s Extragalactic Distance Scale Key Project, which aimed to determine a new state-of-the-art value for the Hubble constant, one of the then-new telescope’s primary science goals. The contribution of NGC 2090 was in calibrating the Tully-Fisher (TF) distance method, by observing Cepheid variable stars in the galaxy. The Cepheid-based measurement from that study in 1998 put NGC 2090 as 37 million light-years away; the newest measurement from 2020, using the TF method, has NGC 2090 slightly farther away, at 40 million light-years. Before and since that project, NGC 2090 has been well studied as a very prominent nearby example of star formation. It has been described as a flocculent spiral, meaning a spiral …

18 November 2024: What kind of astronomical object is this? It doesn’t look quite like the kinds of galaxies, nebulae, star clusters or galaxy clusters which Hubble normally brings us images of. In fact, this is a spiral galaxy, named UGC 10043 — we just happen to be seeing it directly from the side! Located roughly 150 million light-years from Earth in the constellation Serpens, UGC 10043 is one of the somewhat rare spiral galaxies that are seen edge-on. From this point of view, we see the galaxy’s disc as a sharp line through space, overlain with a prominent dust lane. This dust is spread across the spiral arms of UGC 10043, but it looks very thick and cloudy when viewed from the side. You can even see the lights of some active star-forming regions in the arms, shining out from behind the dust. Strikingly, we can also see that the centre of …

11 November 2024: Previously the Hubble Picture of the Week series has featured a jewel in the queen’s hair — a spiral galaxy in the constellation Coma Berenices, named for the hair of the historical Egyptian queen. However, that galaxy is only one of many known in this constellation. This week’s new image from the NASA/ESA Hubble Space Telescope depicts the cosmic tangle that is MCG+05-31-045, a pair of interacting galaxies located 390 million light-years away and a part of the so-called Coma galaxy cluster. The Coma cluster is a particularly rich cluster and contains over a thousand known galaxies. Several can be easily seen with amateur telescopes. Most of them are elliptical galaxies, and that’s typical of a dense galaxy cluster like the Coma cluster: many elliptical galaxies are formed in close encounters between galaxies that stir them up, or even collisions that rip them apart. While the stars in the interacting …

4 November 2024: This Hubble Picture of the week features NGC 1672, a barred spiral galaxy located 49 million light-years from Earth in the constellation Dorado. This galaxy is a multi-talented light show, showing off an impressive array of different celestial lights. Like any spiral galaxy, its disc is filled with billions of shining stars that give it a beautiful glow. Along its two large arms, bubbles of hydrogen gas are made to shine a striking red light by the powerful radiation of newly-forming stars within. Near to the centre lie some particularly spectacular stars; newly-formed and extremely hot, they are embedded in a ring of hot gas and are emitting powerful X-rays. And in the very centre sits an even more brilliant source of X-rays, an active galactic nucleus created by the heated accretion disc around NGC 1672’s supermassive black hole; this makes NGC 1672 a Seyfert galaxy. But a highlight of …

28 October 2024: This image from the NASA/ESA Hubble Space Telescope features the unbarred spiral galaxy NGC 4414, roughly 51 million light-years away from Earth in the constellation Coma Berenices. You can see an old image of NGC 4414 that features Hubble data from 1995 and 1999 here, which was captured as one of the telescope’s primary missions to determine the distance to galaxies. This was achieved as part of an ongoing research effort to study Cepheid variable stars. Cepheids are a special type of variable star with very stable and predictable brightness variations. The period of these variations depends on physical properties of the stars such as their mass and true brightness. This means that astronomers, just by looking at the variability of their light, can find out about the Cepheids' physical nature, which then can be used very effectively to determine their distance. For this reason cosmologists call Cepheids 'standard candles'. …

21 October 2024: The spiral galaxy appearing in this week’s Hubble Picture of the Week is named IC 3225. It looks remarkably as if it’s been launched from a cannon, speeding through space like a comet with a tail of gas streaming from its disc behind it. The scenes that galaxies appear in from Earth’s point of view are fascinating; many seem to hang calmly in the emptiness of space as if hung from a string, while others star in much more dynamic situations! Appearances can be deceiving with objects so far from Earth — IC 3225 itself is about 100 million light-years away — but the galaxy’s location suggests some causes for this active scene, because IC 3225 is one of over 1300 members of the Virgo galaxy cluster. The density of galaxies in the Virgo cluster creates a rich field of hot gas between them, the so-called ‘intracluster medium’, while the …

14 October 2024: The striking spiral galaxy featured in this week’s Hubble Picture of the Week is Messier 90 (M90, also NGC 4569), located in the constellation Virgo. In 2019, an image of M90 was released using data from the older Wide Field and Planetary Camera 2 — data taken in 1994 soon after the camera’s installation. That image has a distinctive stair-step pattern due to the layout of WFPC2’s sensors. WFPC2 was replaced in 2010 by the Wide Field Camera 3, and Hubble used WFC3 when it turned its aperture to Messier 90 again in 2019 and 2023. The resulting data was processed to create this stunning new image, providing a much fuller view of the galaxy’s dusty disc, its gaseous halo and its bright core. The inner regions of M90’s disc are sites of star formation, which is highlighted here by red H-alpha light from nebulae, but this is absent in …

7 October 2024: The sparkling scene depicted in this week’s Hubble Picture of the Week is of the spiral galaxy NGC 5248, located 42 million light-years from Earth in the constellation Boötes. It is also known as Caldwell 45, having been included in a catalogue of visually interesting celestial objects that were known, but weren’t as commonly observed by amateur astronomers as the more famous Messier objects. NGC 5248 is one of the so-called ‘grand design’ spirals, with prominent spiral arms that reach from near the core out through the disc. It also has a faint bar structure in the centre, between the inner ends of the spiral arms, which is not quite so obvious in this visible-light portrait from Hubble. Features like these which break the rotational symmetry of a galaxy have a huge influence on how matter moves through it, and eventually its evolution through time. They feed gas from a …

30 September 2024: Most galaxies we are familiar with fall into one of two easily-identified types. Spiral galaxies are young and energetic, filled with the gas needed to form new stars and sporting spiral arms hosting hot, bright stars. Elliptical galaxies have a much more pedestrian look, their light coming from a uniform population of older and redder stars. But other galaxies require in-depth study to understand: such is the case with NGC 4694, a galaxy located 54 million light-years from Earth in the Virgo galaxy cluster, and the subject of this Hubble Picture of the Week. NGC 4694 has a smooth-looking, armless disc which — like an elliptical galaxy — is nearly devoid of star formation. However its stellar population is still relatively young and new stars are still actively forming in its core, powering the brightness we can see in this image and giving it a markedly different stellar profile from …

23 September 2024: The spiral galaxy IC 1954, located 45 million light-years from Earth in the constellation Horologium, is the star of this Picture of the Week from the Hubble Space Telescope. It sports a glowing bar in its core, two main majestically winding spiral arms and clouds of dark dust across it. An image of this galaxy was previously released in 2021; this week’s image is entirely new and now includes H-alpha data. The improved coverage of star-forming nebulae, which are prominent emitters of the red H-alpha light, can be seen in the numerous glowing, pink spots across the disc of the galaxy. Interestingly, some astronomers posit that the galaxy’s ‘bar’ is actually an energetic star-forming region that just happens to lie over the galactic centre. The new data featured in this image come from a programme to extend the cooperation between multiple observatories: Hubble, the infrared James Webb Space Telescope, and …

16 September 2024: The magnificent galaxy featured in this Hubble Picture of the Week is NGC 1559. It is a barred spiral galaxy located in the constellation Reticulum near the Large Magellanic Cloud, but much more distant at approximately 35 million light-years from Earth. Hubble last visited this object in 2018. The brilliant light captured in this image offers a wealth of information, which thanks to Hubble can be put to use by both scientists and the public. This picture is composed of a whopping ten different images taken by the Hubble Space Telescope, each filtered to collect light from a specific wavelength or range of wavelengths. It spans Hubble’s sensitivity to light, from ultraviolet around 275 nanometres through blue, green and red to near-infrared at 1600 nanometres. This allows information about many different astrophysical processes in the galaxy to be recorded: a notable example is the red 656-nanometre filter used here. Hydrogen …

9 September 2024: The subject of this Hubble Picture of the Week is a spiral galaxy in the constellation Virgo named NGC 5668. It is relatively near to us at 90 million light-years from Earth and quite accessible for astronomers to study with both space- and ground-based telescopes. At first blush, it doesn’t seem like a remarkable galaxy. It is around 90 000 light-years across, similar in size and mass to our own Milky Way galaxy, and its orientation nearly face-on to us shows open spiral arms made of cloudy, irregular patches. One noticeable difference between the Milky Way galaxy and NGC 5668 is that this galaxy is forming new stars 60% more quickly. This fact belies a galaxy with churning clouds and flows of gas, inclement weather that forms excellent conditions for the formation of new stars! Two main drivers of star formation have been identified by astronomers. Firstly, this high-quality Hubble …

2 September 2024: The Hubble Space Telescope has a lot to show in this week’s Picture of the Week. Its view here is studded with stars, many of which appear particularly large and bright thanks to their nearby locations in our own galaxy, and which feature the characteristic diffraction patterns caused by Hubble’s optics. Much further away — around 240 million light-years distant in fact, in the southern constellation Telescopium — is the spiral galaxy IC 4709. Its swirling disc filled with stars and dust bands is beautifully captured, as is the faint halo surrounding it. The compact region at its core might be the most remarkable sight, however: this is an active galactic nucleus (AGN). If IC 4709’s core were just filled with stars, it would not be nearly so bright. Instead it hosts a gargantuan black hole, 65 million times the mass of our Sun. A disc of gas spirals around …

26 August 2024: Looking past its long spiral arms filled with stars and the dark threads of dust crossing it, your eye might be caught by the shining point at the centre of UGC 3478, the spiral galaxy starring in this Hubble Picture of the Week. This point is the galaxy’s nucleus, and indeed there is something special about it: it is a growing giant black hole which astronomers call an active galactic nucleus, or AGN. UGC 3478, located in the constellation Camelopardalis, is what is known as a Seyfert galaxy. This is a type of galaxy with an AGN at its core. Like all such ‘active galaxies’, the brightness that you see here hides a supermassive black hole at the centre of the galaxy. A disc of gas spirals into this black hole, and as the material crashes together and heats up it emits very strong radiation. The spectrum of this radiation …

19 August 2024: Resting near the centre of the northerly constellation Cepheus, high in the northern sky, is the barred spiral galaxy UGC 11861, the subject of the latest Hubble Picture of the Week. UGC 11861 is located 69 million light-years away from Earth — which may seem a vast distance, but it’s just right for Hubble to grab this majestic shot of the galaxy’s spiral arms and the short but brightly glowing bar in its centre. Among the cloudy gases and the dark wisps of dust, this galaxy is actively forming new stars, visible in the glowing blue patches in its outer arms. This activity has resulted in three supernova explosions being spotted in and nearby UGC 11861, in 1995, 1997 and 2011. The earlier two were both Type II supernovae, a kind which results from the collapse of a massive star at the end of its life. This Hubble image was …

12 August 2024: The subject of this week’s circular Hubble Picture of the Week is situated in the Perseus Cluster, also known as Abell 426, 320 million light-years from Earth. It’s a barred spiral galaxy known as MCG+07-07-072, seen here among a number of photobombing stars that are much closer to Earth than it is. MCG+07-07-072 has quite an unusual shape, for a spiral galaxy, with thin arms emerging from the ends of its barred core to draw a near-circle around its disc. It is classified, using a common extension of the basic Hubble scheme, as an SBc(r) galaxy: the c denotes that its two spiral arms are loosely wound, each only performing a half-turn around the galaxy, and the (r) is for the ring-like structure they create. Rings in galaxies come in quite a few forms, from merely uncommon, to rare and astrophysically important! Lenticular galaxies are a type that sit between …

5 August 2024: This Hubble Picture of the Week features the galaxy LEDA 857074, located in the constellation Eridanus. LEDA 857074 is a barred spiral galaxy, with partially broken spiral arms. It also has a particularly bright spot right in its bar: this is a supernova snapped by Hubble, named SN 2022ADQZ, and quite relevant to this Picture of the Week. The NASA/ESA Hubble Space Telescope has observed a vast range of celestial objects, from galaxies, to nebulae, to star clusters, to planets in the Solar System and beyond. Observing programmes usually seek to gather data so that astronomers can answer a specific question. Naturally, this means most scheduled observations target an object that astronomers have already researched. Some are famous, like the Crab Nebula or the globular cluster Omega Centauri; others might not be so well known to the public, but still be featured in hundreds of scientific papers, such as the …

29 July 2024: The Hubble Picture of the Week this week reveals the subtle glow of the galaxy named IC 3430, located 45 million light-years from Earth in the constellation Virgo. It is part of the Virgo cluster, a rich collection of galaxies both large and small, many of which are very similar in type to this diminutive galaxy. IC 3430 is a dwarf galaxy, a fact well reflected by this view from Hubble, but it is more precisely known as a dwarf elliptical or dE galaxy. Like its larger cousins, this galaxy has a smooth, oval shape lacking any recognisable features like arms or bars, and it is bereft of gas to form very many new stars. Interestingly, IC 3430 does feature a core of hot, massive blue stars, an uncommon sight in elliptical galaxies that indicates recent star-forming activity. It’s believed that ram pressure from the galaxy ploughing through gas within …

22 July 2024: In this week’s Hubble Picture of the Week we are treated to a wonderfully detailed snapshot of NGC 3430. A spiral galaxy, it lies 100 million light-years from Earth in the constellation Leo Minor. Several other galaxies are located relatively nearby to this one, just out of frame; one is close enough that gravitational interaction is driving some star formation in NGC 3430. That NGC 3430 is such a fine example of a galactic spiral may be why it ended up as part of the sample that Edwin Hubble used to define his classification of galaxies. Namesake of the Hubble Space Telescope, in 1926 he authored a paper which classified some four hundred galaxies by their appearance — as either spiral, barred spiral, lenticular, elliptical or irregular. This straightforward typology proved immensely influential, and the modern, more detailed schemes that astronomers use today are still based on it. NGC 3430 …