Picture of the Week 2023

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 …