Spiral Galaxy M77 as seen by Subaru

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M77 aka NGC 1068 is a spiral galaxy located relatively close to our Milky Way. At its center lies a supermassive black hole about 10 million times the mass of the Sun. As enormous amounts of energy are released around the black hole, M77 is known as an active galaxy.

Because of its proximity, M77 has been extensively studied across the electromagnetic spectrum, from X-rays to radio waves, using various telescopes, including the Subaru Telescope and ALMA. Recently, observations with the Subaru Telescope's Hyper Suprime-Cam (HSC) have revealed evidence that M77 experienced a previously hidden minor merger with a low-mass satellite galaxy billions of years ago.

Image Credit: NAOJ/SDSS/David Hogg/Michael Blanton

Image Processing: Ichi Tanaka

Image enhancement: Jean-Baptiste Faure

Intermediate Spiral Galaxy NGC 3137

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In this Hubble picture, a spiral galaxy glittering with star clusters is the center of attention. NGC 3137 is located 53 million light-years away in the constellation Antlia (The Air Pump). As a nearby spiral galaxy, this target offers astronomers an excellent opportunity to study the cycle of stellar birth and death, as well as giving researchers a glimpse of a galactic system similar to our own.

NGC 3137 is of particular interest to astronomers because it travels through space with a group of galaxies that is thought to be similar to the Local Group, the galaxy group that contains the Milky Way. Similar to the Local Group, the NGC 3175 group contains two large spiral galaxies: NGC 3137 and NGC 3175, which Hubble has also observed. In the Local Group, the largest members are the Milky Way galaxy and Andromeda, another spiral galaxy. In addition to two large spiral galaxies, both groups also contain a number of smaller dwarf galaxies, although it's not yet known how many of these tiny companions the NGC 3175 group has; researchers have found more than 500 dwarf galaxy candidates. By studying this nearby galaxy group, astronomers can learn about the dynamics of our own galactic home.

NGC 3137 is revealed in fantastic detail by Hubble. This image is crafted from observations in six different colour bands, creating a view that highlights several facets of this beautiful spiral. The galaxy's center, which is encircled by a network of fine, dusty clouds, hosts a black hole estimated to be 60 million times more massive than the Sun. NGC 3137 is highly inclined from our point of view, giving a unique perspective on its loose, feathery spiral structure. A couple of photobombing Milky Way stars and a smattering of far more distant background galaxies complete the image.

As stunning as each of these features may be, it's the galaxy's brilliant star clusters that steal the show. The galaxy is peppered with dense clusters of bright blue stars and glowing red gas clouds, which signal the presence of hot, young stars still encased in their birth nebulae.

Unsurprisingly, these star clusters are exactly what has drawn Hubble's keen eye. Researchers are using Hubble to carry out an observing programme focusing on star clusters in 55 nearby galaxies. The data collected will help astronomers identify star clusters and the glowing nebulae that surround them, providing a way to measure the ages of stars in galaxies like NGC 3137. These observations give an in-depth view of stellar life in spiral galaxies, from the young stars still in the process of forming to the ancient stellar populations that grew up in the early years of their galactic hosts.

The PHANGS-HST programme for which these observations were taken is part of a larger effort by some of the most powerful observatories on (and around) Earth. Hubble contributes greatly to this massive undertaking, which combines data from the James Webb Space Telescope and the Atacama Large Millimetre/submillimetre Array (ALMA). Together, Hubble's powerful optical and ultraviolet capabilities, Webb's sensitive infrared eyes, and ALMA's broad network of radio dishes bring us an unmatched view of star formation in the local Universe.

Image Credit: ESA/Hubble and NASA, D. Thilker and the PHANGS-HST Team

Image enhancement: Jean-Baptiste Faure

Barred Spiral Lenticular Galaxy NGC 1269

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This image of NGC 1269 was taken utilizing the Department of Energy-fabricated Dark Energy Camera (DECam), which is mounted on the U.S. National Science Foundation Víctor M. Blanco 4-meter Telescope at NSF Cerro Tololo Inter-American Observatory, a Program of NSF NOIRLab.

NGC 1269 is an early-type spiral galaxy located about 33 million light-years from Earth in the constellation Eridanus. A bar, a feature common to many spiral galaxies, slices through the center of the galaxy. Surrounding the galactic core are both inner and outer disks, seeming to form "wheels" around the core. Their presence is thought to be the result of a merger with another galaxy, and the inner disk is also believed to have been further shaped by density waves radiating outward from the galactic center.

Data for this image came from the archive of the Dark Energy Survey (DES), operated by the DOE and NSF between 2013 and 2019 with the specially-designed DECam. The survey sought to study the nature of the elusive dark matter by imaging hundreds of millions of galaxies. Today, the DECam is available to other scientists for use on the Blanco telescope.

Image Credit: Dark Energy Survey/DOE/FNAL/DECam/CTIO/NOIRLab/NSF/AURA

Image processing: R. Colombari & M. Zamani (NSF NOIRLab)

Image enhancement: Jean-Baptiste Faure

Barred Spiral Galaxy NGC 646 by Euclid

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Galaxy NGC 646 sparkles like a cosmic holiday garland in this new image from the European Space Agency's Euclid space telescope. This large barred spiral galaxy is located in the constellation Hydrus and was discovered in 1834 by the British astronomer John Herschel (the son of William Herschel). The galaxy is moving away from us at about 8145 km per second. It's located roughly 392 million light-years from Earth, which means its light takes hundreds of millions of years to reach us. Although this sounds very far, NGC 646 is actually quite close compared to the billions of galaxies that Euclid will observe during its six-year mission.

By the end of 2026, ESA and the Euclid Consortium will release the first year of observations, covering about 1900 square degrees of the sky (approximately 14% of the total survey area). These images will reveal hundreds of thousands of galaxies in exquisite detail, offering new insights into how galaxies form and evolve – and why barred galaxies become more common as the Universe ages.

In this image, NGC 646 appears close to a smaller galaxy to the left, called PGC 6014. They look like neighbours, but they're actually about 45 million light-years apart, with PGC 6014 at a distance of 347 million light-years from us. So, any gravitational interaction between them, if it exists, would be very weak and short-lived. Image Credit: ESA/Euclid/Euclid Consortium/NASA

Image processing by the Euclid Science Ground Segment and M. Schirmer (MPIA)

Image enhancement: Jean-Baptiste Faure

Spiral Galaxy NGC 4571

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A star-studded spiral galaxy shines in this Hubble Space Telescope picture. This galaxy is called NGC 4571, and it's situated about 60 million light-years away in the constellation Coma Berenices. NGC 4571 dominates the scene with its feathery spiral structure and sparkling star clusters.

The galaxy's dusty spiral arms are dotted with brilliant pink nebulae that contain massive young stars. Though the star-forming clouds that are seen here are heated to roughly 10 000 degrees by searing ultraviolet light from the young stars at their cores, stars get their start in much chillier environments. The sites of star birth are giant molecular clouds tens to hundreds of light-years across, in which the temperature hovers just a few tens of degrees above absolute zero.

The dramatic transformation from freezing gas cloud to fiery young star happens thanks to the immense pull of gravity, which collects gas into dense clumps within a star-forming cloud. As these clumps yield to gravity's pull and collapse inward, they eventually become hot and dense enough to spark nuclear fusion in their centers and begin to shine. The glowing clouds in this image surround particularly massive stars that are hot enough to ionise the gas of their birthplaces.

A Hubble image of NGC 4571 was previously released in 2022, using data from an observing programme the combines data from leading observatories like Hubble, the James Webb Space Telescope, and the Atacama Large Millimeter/submillimeter Array to study star formation in nearby spiral galaxies like NGC 4571. The new image released today adds data from a programme that seeks to understand how dust affects our observations of young stars deeply embedded within their natal clouds.

Image Credit: ESA/Hubble and NASA, F. Belfiore, J. Lee and the PHANGS-HST Team

Image enhancement: Jean-Baptiste Faure

Edge-On Spiral Galaxy UGC 10043

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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.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 the galaxy sports a glowing, almost egg-shaped "bulge", rising far above and below the disc. All spiral galaxies have a bulge like this one as part of their structure, containing stars that orbit the galactic center on paths above and below the whirling disc; it's a feature that isn't normally obvious in pictures of galaxies. The unusually large size of this bulge compared to the galaxy's disc is possibly thanks to UGC 10043 siphoning material from a nearby dwarf galaxy. This may also be why the disc is warped, bending up at one end and down at the other.

Like most of the full-colour Hubble images released by Hubble, this image is a composite, made up of several individual snapshots taken by Hubble at different times and capturing different wavelengths of light. You can see the exact images used in the sidebar on this page. A notable aspect of this image is that the two sets of Hubble data used were collected 23 years apart, in 2000 and 2023! Hubble's longevity doesn't just afford us the ability to produce new and better images of old targets; it also provides a long-term archive of data which only becomes more and more useful to astronomers.

Image Credit: ESA/Hubble and NASA, R. Windhorst, W. Keel

Image enhancement: Jean-Baptiste Faure

Barred Spiral Galaxy NGC 1672

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This Hubble picture 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 this image is the most fleeting and temporary of these lights: supernova SN 2017GAX, visible in just one of the six Hubble images that make up this composite image. This was a Type I supernova caused by the core-collapse and subsequent explosion of a giant star, going from invisibility to a new light in the sky in just a matter of days. In that image from later that year, the supernova is already fading, and so is only just visible here as a small green dot, just below the crook of the spiral arm on the right side. In fact this was on purpose, as astronomers wanted to look for any companion star that the supernova progenitor may have had – something impossible to spot beside a live supernova! For a closer look at the supernova's appearance, you can compare the two images with this slider tool.

Image Credit: ESA/Hubble and NASA, O. Fox, L. Jenkins, S. Van Dyk, A. Filippenko, J. Lee and the PHANGS-HST Team, D. de Martin (ESA/Hubble), M. Zamani (ESA/Hubble)

Image enhancement: Jean-Baptiste Faure

Intermediate Spiral Galaxy M90 (NGC 4569)

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The striking spiral galaxy featured in this picture of the Week is M90 (Messier 90, 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 the rest of the galaxy. M90 sits among the galaxies of the relatively nearby Virgo Cluster, and the course of its orbit took it on a path near the cluster's center about three hundred million years ago. The density of gas in the inner cluster weighed on M90 like a strong headwind, stripping enormous quantities of gas from the galaxy and creating the diffuse halo that can be seen around it here. This gas is no longer available for M90 to form new stars with, and it will eventually fade as a spiral galaxy as a result.

M90 is located 55 million light-years from Earth, but it's one of the very few galaxies getting closer to us. Its orbit through the Virgo cluster has accelerated it so much that it’s in the process of escaping the cluster entirely, and by happenstance it's moving in our direction – other galaxies in the Virgo cluster have been measured at similar speeds, but in the opposite direction. Over the coming billions of years, we will be treated to a yet better view of M90 while it evolves into a lenticular galaxy.

Image Credit: ESA/Hubble and NASA, D. Thilker, J. Lee and the PHANGS-HST Team

Image enhancement: Jean-Baptiste Faure

Intermediate Spiral Galaxy NGC 5248

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The sparkling scene depicted in this Hubble picture 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 center, 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 galaxy's outer reaches to inner star-forming regions, and even to a galaxy's central black hole where it can kick-start an active galactic nucleus.

These flows of gas have shaped NGC 5248 in a big way; it has many bright "starburst regions" of intense star formation spread across its disc, and it is dominated by a population of young stars. The galaxy even has two very active, ring-shaped starburst regions around its nucleus, filled with young clusters of stars. These "nuclear rings" are remarkable enough, but normally a nuclear ring tends to block gas from getting further into the core of a galaxy. NGC 5248 having a second ring inside the first is a marker of just how forceful its flows of matter and energy are! Its relatively nearby, highly visible starburst regions make the galaxy a target for professional and amateur astronomers alike.

Image Credit: ESA/Hubble and NASA, F. Belfiore, J. Lee and the PHANGS-HST Team

Image enhancement: Jean-Baptiste Faure

Interacting Galaxies Arp 107 as seen by Webb

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An interaction between an elliptical galaxy and a larger spiral galaxy, collectively known as Arp 107, seems to have given the spiral a happier outlook thanks to the two bright "eyes" and the wide semicircular "smile" that have resulted. This image is a composite, combining observations from Webb's MIRI (Mid-InfraRed Instrument) and NIRCam (Near-InfraRed Camera).

NIRCam highlights the stars within both galaxies and reveals the connection between them: a transparent, white bridge of stars pulled from both galaxies during their passage. MIRI data, represented in orange-red, show star-forming regions and dust that is composed of soot-like organic molecules known as polycyclic aromatic hydrocarbons. MIRI also provides a snapshot of the bright nucleus of the large spiral, home to a supermassive black hole.

The spiral galaxy is classified as a Seyfert galaxy, one of the two largest groups of active galaxies, along with galaxies that host quasars. Seyfert galaxies aren't as luminous or as distant as quasars, so they are better places to study similar phenomena in lower-energy light, like infrared.

This region is much like the Cartwheel Galaxy, one of the first interacting galaxies that Webb observed. Arp 107 may have turned out very similar in appearance to the Cartwheel, but since the smaller elliptical galaxy had an off-centre collision instead of a direct hit, the spiral galaxy got away with only its spiral arms being disturbed.

The collision isn't as bad as it sounds. Although there was much star formation occurring before, collisions between galaxies can compress gas, improving the conditions needed for more stars to form. On the other hand, as Webb reveals, collisions also disperse a lot of gas, potentially depriving new stars of the material they need to form.

Webb has captured these galaxies in the process of merging, which will take hundreds of millions of years. As the two galaxies rebuild after the chaos of their collision, Arp 107 may lose its smile, but it will inevitably turn into something just as interesting for future astronomers to study.

Arp 107 is located 465 million light-years from Earth in the constellation Leo Minor.

Image Credit: NASA, ESA, CSA, STScI

Image enhancement: Jean-Baptiste Faure

Barred Spiral Galaxy NGC 1559

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The magnificent galaxy featured in this Hubble picture 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 atoms which get ionised can emit light at this particular wavelength, called H-alpha emission. New stars forming in a molecular cloud, made mostly of hydrogen gas, emit copious amounts of ultraviolet light which is absorbed by the cloud, but which ionises it and causes it to glow with this H-alpha light. Therefore, filtering to detect only this light provides a reliable means to detect areas of star formation (called H II regions), shown in this image by the bright red and pink colours of the blossoming patches filling NGC 1559's spiral arms.

These ten images come from six different observing programmes with Hubble, running from 2009 all the way up to the present year. These programmes were led by teams of astronomers from around the world with a variety of scientific goals, ranging from studying ionised gas and star formation, to following up on a supernova, to tracking variable stars as a contribution to calculating the Hubble constant. The data from all of these observations live on in the Hubble archive, available for anyone to use – not only for new science, but also to create spectacular images like this one! This image of NGC 1559, then, is a reminder of the incredible opportunities that the Hubble Space Telescope has provided and continues to provide.

Image Credit: ESA/Hubble and NASA, F. Belfiore, W. Yuan, J. Lee and the PHANGS-HST Team, A. Riess, K. Takáts, D. de Martin and M. Zamani (ESA/Hubble)

Image enhancement: Jean-Baptiste Faure

Intermediate Spiral Galaxy NGC 6744

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Behold NGC 6744, a spiral galaxy bearing similarities to our home galaxy, the Milky Way. This cosmic twin is captured here in stunning detail by the Dark Energy Camera (DECam) on the Víctor M. Blanco 4-meter Telescope at the U.S. National Science Foundation Cerro Tololo Inter-American Observatory (CTIO), a Program of NSF NOIRLab in Chile. Located around 30 million light-years away in the constellation Pavo, NGC 6744 exhibits a luminous core and spiral arms spanning 175,000 light-years across, a larger but similar anatomy to our Milky Way. Moreover, to the lower right of NGC 6744, at the end of the spiral arm, is a faint blob. This is its companion galaxy known as NGC 6744A. The companionship between these galaxies is analogous to that between the Milky Way and its dwarf companion the Large Magellanic Cloud. Though it’s impossible to get an external view of our galaxy, these similarities offer insight into how the Milky Way might look to a distant observer.

This is one of the deepest images of NGC 6744 ever taken, and keen observers can spy the faint extended arm on the left hand side of the galaxy – rarely visible in most images.

This image is part of the DESI Legacy Imaging Surveys, an ambitious effort to construct the largest 3D map of the night sky with the DOE-built DECam on the Blanco Telescope at NSF CTIO and other Programs of NSF NOIRLab.

Image Credit: Dark Energy Survey/DOE/FNAL/DECam/CTIO/NOIRLab/NSF/AURA

Image processing: R. Colombari and M. Zamani (NSF NOIRLab)

Image enhancement: Jean-Baptiste Faure

Seyfert Spiral Galaxy UGC 3478

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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 center of UGC 3478, the spiral galaxy starring in this Hubble picture. 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 center 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 includes hard X-ray emission, which clearly mark it out from the stars in the galaxy. Despite the strong brightness of the compact central region, we can still clearly see the disc of the galaxy around it, which makes the galaxy a Seyfert galaxy.

Many active galaxies are known to astronomers at vast distances from Earth, thanks to the great brightness of their nuclei highlighting them next to other, dimmer galaxies. At 128 million light-years from Earth, UGC 3478 is positively neighbourly to us. The data used to make this image comes from a Hubble survey of nearby powerful AGNs found in relatively high-energy X-rays, like this one, which it is hoped can help astronomers to understand how the galaxies interact with the supermassive black holes at their hearts.

Image Credit: ESA/Hubble and NASA, M. Koss, A. Barth

Image enhancement: Jean-Baptiste Faure

Spiral Galaxy NGC 3810

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Measuring the distance to truly remote objects like galaxies, quasars and galaxy clusters is a crucial task in astrophysics, particularly when it comes to studying the early Universe, but it's a difficult one. Only in the case of a few nearby objects like the Sun, planets and some nearby stars can we measure their distances directly. Beyond that, various indirect methods need to be used; one of the most important is by examining Type Ia supernovae, and this is where the Hubble Space Telescope comes in.

NGC 3810, the galaxy featured in this image, was the host of a Type Ia supernova in 2022. In early 2023 Hubble focused on this and a number of other galaxies to closely examine recent Type Ia supernovae. This kind of supernova results from a white dwarf exploding, and they all have a very consistent brightness. That allows them to be used to measure distances: we know how bright a Type Ia supernova should be, so we can tell how far away it must be from how dim it appears. One uncertainty in this method is that intergalactic dust in between Earth and a supernova blocks some of its light. How do you know how much of the reduction in light is caused by distance, and how much by dust? With the help of Hubble, there's a clever workaround: take images of the same Type Ia supernovae in ultraviolet light, which is almost completely blocked by dust, and in infrared light, which passes through dust almost unaffected. By carefully noting how much light comes through at each wavelength, the relationship between supernova brightness and distance can be calibrated to account for dust. Hubble can observe both these wavelengths of light in great detail with the same instrument. That makes it the perfect tool for this experiment, and indeed, some of the data used to make this beautiful image of NGC 3810 were focused on its 2022 supernova. You can see it as a point of light just below the galactic nucleus, or in the annotated image here.

There are many ways to measure cosmic distances; because Type Ia supernovae are so bright, they are one of the most useful and accurate tools, when they're spotted. Many other methods must be used as well, either as an independent check against other distance measurements or to measure at much closer or farther distances. One such method that also works for galaxies is comparing their rotation speed to their brightness; based on that method, NGC 3810 is found to be 50 million light-years from Earth.

Image Credit: ESA/Hubble and NASA, D. Sand, R. J. Foley

Image enhancement: Jean-Baptiste Faure

Dwarf Barred Spiral Galaxy IC 776

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Featured in this picture is the dwarf galaxy IC 776. This swirling collection of stars new and old is located in the constellation Virgo – in fact, in the Virgo galaxy cluster – 100 million light-years from Earth. While a dwarf galaxy, it's also been classified as an SAB-type or "weakly barred" spiral, one study naming it a "complex case" in morphology. This highly detailed view from Hubble demonstrates that complexity well. IC 776 has a ragged, disturbed disc that nevertheless looks to spiral around the core, and arcs of star-forming regions.

This image is from an observation programme dedicated to the study of dwarf galaxies in the Virgo cluster, searching for sources of X-rays in such galaxies. X-rays are often emitted by accretion discs, where material that is drawn into a compact object by gravity crashes together and forms a hot, glowing disc. The compact object can be a white dwarf or neutron star in a binary pair, stealing material from its companion star, or it can be the supermassive black hole at the heart of a galaxy, devouring all around it. Dwarf galaxies like IC 776, travelling through the Virgo cluster, experience a pressure from the intergalactic gas which can both stimulate star formation and feed the central black hole in a galaxy. That can create energetic accretion discs, hot enough to emit X-rays.

While Hubble is not able to see X-rays, it can coordinate with X-ray telescopes such as NASA's Chandra, revealing the sources of this radiation in high resolution using visible light. Dwarf galaxies are thought to be very important for our understanding of cosmology and the evolution of galaxies. As with many areas of astronomy, the ability to examine these galaxies across the electromagnetic spectrum is critical to their study.

Image Credit: ESA/Hubble and NASA, M. Sun

Image enhancement: Jean-Baptiste Faure

Barred Spiral Galaxy NGC 3059

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This picture features the barred spiral galaxy NGC 3059, which lies about 57 million light-years from Earth. The data used to compose this image were collected by Hubble in May 2024, as part of an observing programme that studied a number of galaxies. All the observations were made using the same range of filters: partially transparent materials that allow only very specific wavelengths of light to pass through.

Filters are used extensively in observational astronomy, and can be calibrated to allow either extremely narrow or somewhat broader ranges of light through. Narrow-band filters are invaluable from a scientific perspective because certain light wavelengths are associated with specific physical and chemical processes. For example, under particular conditions, hydrogen atoms are known to emit red light with wavelength value of 656.46 nanometers. Red light at this wavelength is known as H-alpha emission, or the "H-alpha line". It is very useful to astronomers because its presence acts as an indicator of certain physical processes and conditions; it is often a tell-tale sign of new stars being formed, for example.

Thus, narrow-band filters calibrated to allow H-alpha emission through can be used to identify regions of space where stars are forming.

Such a filter was used for this image, the narrow-band filter called F657N or the H-alpha filter. The F stands for filter, and the N stands for narrow. The numerical value refers to the peak wavelength (in nanometers) that the filter lets through. The eagle-eyed amongst you may have noticed that 657 is very close to the 656.46 H-alpha line's wavelength. Data collected using five other filters contributed to this image as well, all of which were wide-band filters; meaning that they allow a wider range of light wavelengths through. This is less useful for identifying extremely specific lines (such as the H-alpha line) but still enables astronomers to explore relatively specific parts of the electromagnetic spectrum. In addition, collectively the information from multiple filters can be used to make beautiful images such as this one.

Image Credit: ESA/Hubble and NASA, D. Thilker

Image enhancement: Jean-Baptiste Faure

Barred Spiral Galaxy NGC 4731

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The barred spiral galaxy NGC 4731 lies among the galaxies of the Virgo cluster, in the constellation Virgo, and is located 43 million light-years from Earth. This highly detailed image was created using six different filters. The abundance of colour illustrates the galaxy's billowing clouds of gas, dark dust bands, bright pink star-forming regions and, most obviously, the long, glowing bar with trailing arms.

Barred spiral galaxies outnumber both regular spirals and elliptical galaxies put together, numbering around 60% of all galaxies. The visible bar structure is a result of orbits of stars and gas in the galaxy lining up, forming a dense region that individual stars move in and out of over time. This is the same process that maintains a galaxy's spiral arms, but it is somewhat more mysterious for bars: spiral galaxies seem to form bars in their centers as they mature, accounting for the large number of bars we see today, but can also lose them later on as the accumulated mass along the bar grows unstable. The orbital patterns and the gravitational interactions within a galaxy that sustain the bar also transport matter and energy into it, fuelling star formation. Indeed, the observing programme studying NGC 4731 seeks to investigate this flow of matter in galaxies.

Beyond the bar, the spiral arms of NGC 4731 stretch out far past the confines of this close-in Hubble view. The galaxy's elongated arms are thought to result from gravitational interactions with other, nearby galaxies in the Virgo cluster.

Image Credit: ESA/Hubble and NASA, D. Thilker

Image enhancement: Jean-Baptiste Faure

Spiral Galaxy NGC 4689

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This picture shows the jewel-bright spiral galaxy NGC 4689, which lies 54 million light-years from Earth in the constellation Coma Berenices. This constellation has the distinction of being the only one of the 88 constellations officially recognised by the International Astronomical Union (IAU) to be named after an historical figure, Queen Berenice II of Egypt. The latin word "coma" references her hair, meaning that NGC 4689 can be said to be found in the hair of a queen. Some people of Berenice's time would have meant this quite literally, as the story goes that her court astronomer thought that a missing lock of Berenice's hair had been catasterised (a word meaning "placed amongst the stars") by the gods: hence the name of the constellation, Coma Berenices.

NGC 4689 holds an interesting – albeit less royal – place in modern astronomy too. The Universe is so incredibly vast that at a distance of a mere 54 million light-years NGC 4689 is relatively nearby for a galaxy. This image has been made using data from two sets of observations, one made in 2019 and 2024, both of which were made as a part of programmes that observed multiple "nearby" galaxies. The 2024 observing programme is an interesting example of how Hubble – a relatively old but extraordinarily productive telescope – can support the work of the technologically cutting-edge Webb telescope. Observations collected by Webb stand to transform our understanding of how galaxies transform and evolve over time, by providing data of an unprecedented level of detail and clarity. However, thanks to their complementary capabilities, new observations from Hubble – such as those used to create this image – can assist the work done using Webb. In this case, the Hubble data were collected in order to get a more accurate grasp of the stellar populations of nearby galaxies, which is crucial to understanding the evolution of galaxies. Thus, NGC 4689 is playing an important role in developing our understanding of how all galaxies evolve. In fact, it is observed enough that it has been the subject of a Hubble Picture of the Week before, in 2020.

Image Credit: ESA/Hubble and NASA, D. Thilker, J. Lee and the PHANGS-HST Team

Image enhancement: Jean-Baptiste Faure

Spiral Galaxy ESO 422-41

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This Hubble Picture of the Week depicts the spiral galaxy ESO 422-41, which lies about 34 million light-years from Earth in the constellation Columba. The patchy, star-filled structure of the galaxy's spiral arms and the glow from its dense core are laid out in intricate detail here by Hubble's Advanced Camera for Surveys. Images of this galaxy have, however, a decades-long history.

The name ESO 422-41 comes from its identification in the European Southern Observatory (B) Atlas of the Southern Sky. In the times before automated sky surveys with space observatories such as ESA's Gaia, many stars, galaxies and nebulae were discovered by means of large photographic surveys. Astronomers used the most advanced large telescopes of the time to produce hundreds of photographs, covering an area of the sky. They later studied the resulting photographs, attempting to catalogue all the new astronomical objects revealed.

In the 1970s a new telescope at ESO's La Silla facility in Chile performed such a survey of the southern sky, which still had not been examined in as much depth as the sky in the north. At the time, the premier technology for recording images was glass plates treated with chemicals. The resulting collection of photographic plates became the ESO Atlas of the Southern Sky. Astronomers at ESO and in Uppsala, Sweden collaborated to study the plates, recording hundreds of galaxies – ESO 422-41 being just one of those – star clusters, and nebulae. Many were new to astronomy.

Astronomical sky surveying has since transitioned through digital, computer-aided surveys such as the Sloan Digital Sky Survey and the Legacy Surveys, to surveys made by space telescopes including Gaia and the Wide-Field Infrared Survey Explorer. Even so, photographic sky surveys contributed immensely to astronomical knowledge for decades, and the archives of glass plates serve as an important historical reference for large swathes of the sky. Some are still actively used today, for instance to study variable stars through time. And the objects that these surveys revealed, including ESO 422-41, can now be studied in depth by telescopes such as Hubble.

Image Credit: ESA/Hubble and NASA, C. Kilpatrick

Image enhancement: Jean-Baptiste Faure

Barred Spiral Galaxy NGC 1559 as seen by Webb

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This image features the barred spiral galaxy NGC 1559 as seen by the James Webb Space Telescope. The galaxy hosts a visible central region with a distinct open pattern in the loosely-wound spiral arms. NGC 1559 resides approximately 35 million light-years away in the little-observed southern constellation Reticulum (The Reticule).

The data featured in this portrait make use of two of Webb's instruments: the Mid-InfraRed Instrument (MIRI) and Near-InfraRed Camera (NIRCam). Here MIRI captures the glow of interstellar dust grains, which trace out the interstellar medium, the fuel for future star formation. NIRCam shows the light from stars, even young stars hidden behind prodigious amounts of dust. NIRCam also captures emission from ionised nebulae around young stars.

The data were collected by the PHANGS team as part of an observing programme in which Webb will observe 55 galaxies that have also been mapped by the Atacama Large Millimeter/submillimeter Array (ALMA) radio telescope, the Hubble Space Telescope and more. By combining Webb's unprecedented view of the dust and stars with data from these other facilities, the team aims to obtain a new, highly detailed view of how stars are born, live, and die in galaxies across the Universe. This is also a Treasury programme, which means that the data will have no exclusive access period and so the scientific community (and others, including the general public) can access the data immediately. This has the advantage that more research can be done with the data more quickly.

NGC 1559 has massive spiral arms that abound with star formation, and it is receding from us at a speed of about 1300 kilometers per second. Although NGC 1559 appears to sit near one of our nearest neighbours in the sky – the Large Magellanic Cloud (LMC) – this is just a trick of perspective. In reality, NGC 1559 is physically nowhere near the LMC in space; in fact it truly is a loner, lacking the company of any nearby galaxies or membership of any galaxy cluster. NGC 1559 may be alone in space, but with Webb we are admiring from far away.

Image Credit: ESA/Webb, NASA and CSA, A. Leroy, J. Lee and the PHANGS Team

Image enhancement: Jean-Baptiste Faure