Rosette Nebula NGC 2237 and Open Cluster NGC 2244

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Cradled within the fiery petals of the Rosette Nebula (NGC 2237) is NGC 2244, the young star cluster which it nurtured. The cluster's stars light up the nebula in vibrant hues of red, gold and purple, and opaque towers of dust rise from the billowing clouds around its excavated core. This image, captured by 570-megapixel Department of Energy-fabricated Dark Energy Camera (DECam), mounted on the U.S. National Science Foundation Víctor M. Blanco 4-meter Telescope at Cerro Tololo Inter-American Observatory, a Program of NSF NOIRLab, is being released in celebration of NOIRLab's fifth anniversary.

Image Credit: CTIO/NOIRLab/DOE/NSF/AURA

Image Processing: T.A. Rector (University of Alaska Anchorage/NSF NOIRLab), D. de Martin and M. Zamani (NSF NOIRLab)

Open Cluster Westerlund 1 as seen by Webb

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The open cluster Westerlund 1, showcased in this new Webb picture, is located roughly 12 000 light-years away in the southern constellation Ara (the Altar) where it resides behind a huge interstellar cloud of gas and dust. It was discovered in 1961 from Australia by Swedish astronomer Bengt Westerlund. Westerlund 1 is an incomparable natural laboratory for the study of extreme stellar physics, helping astronomers to find out how the most massive stars in our Galaxy live and die.

The unique draw of Westerlund 1 is its large, dense, and diverse population of massive stars, which has no counterpart in other known Milky Way galaxy clusters in terms of the number of stars and the richness of spectral types and evolutionary phases. All stars identified in this cluster are evolved and very massive, spanning the full range of stellar classifications including Wolf-Rayet stars, OB supergiants, yellow hypergiants (nearly as bright as a million Suns) and luminous blue variables. Because such stars have a rather short life, Westerlund 1 is very young, astronomically speaking. Astronomers estimate the cluster's age to be somewhere between 3.5 and 5 million years (its exact age is still a matter of debate), making it a newborn cluster in our galaxy. In the future, it is believed that it will likely evolve from an open cluster into a globular cluster. These are roughly spherical, tightly packed collections of old stars bound together by gravity.

Currently, only a handful of stars form in our galaxy each year, but in the past the situation was different. The Milky Way galaxy used to produce many more stars, likely hitting its peak of churning out dozens or hundreds of stars per year about 10 billion years ago and then gradually declining ever since. Astronomers think that most of this star formation took place in massive clusters of stars, known as "super star clusters". These are young clusters of stars that contain more than 10,000 times the mass of the Sun, packed into an unbelievably small volume. They represent the most extreme environments in which stars and planets can form. Only a few super star clusters still exist in our galaxy – of which Westerlund 1 is one – but they offer important clues about this earlier era when most of our galaxy's stars formed.

Westerlund 1 is an impressive example of a super star cluster: it contains hundreds of very massive stars, some shining with a brilliance of almost one million Suns and others two thousand times larger than the Sun (as large as the orbit of Saturn). Indeed, if the Solar System was located at the heart of this remarkable cluster, our sky would be full of hundreds of stars as bright as the full Moon. It appears to be the most massive compact young cluster yet identified in the Milky Way galaxy: astronomers believe that this extreme cluster contains between 50 000 and 100 000 times the mass of the Sun, yet all of its stars are located within a region less than six light-years across. Even so, it is the biggest of these remaining super star clusters in the Milky Way galaxy, and the closest super star cluster to Earth. These qualities make Westerlund 1 an excellent target for studying the impact of a super star cluster's environment on the formation process of stars and planets, as well as the evolution of stars over a broad range of masses.

The huge population of massive stars in Westerlund 1 suggests that it will have a very significant impact on its surroundings. The cluster contains so many massive stars that in a time span of less than 40 million years, it will be the site of more than 1 500 supernovae. This super star cluster now provides astronomers with a unique perspective towards one of the most extreme environments in the Universe. Westerlund 1 will certainly provide new opportunities in the long-standing quest for more and finer details about how stars, and especially massive stars, form.

This image was captured as part of the The Extended Westerlund 1 and 2 Open Clusters Survey (EWOCS) with Webb's Near-InfraRed Camera (NIRCam). This survey is a dedicated Webb program (GO 1905, PI: M. G. Guarcello) that aims to study star and planet formation and stellar evolution in starburst regions in Westerlund 1 and Westerlund 2, two of the closest super star clusters to the Sun.

With its unparalleled performance in the infrared, Webb offers astronomers the opportunity to unveil the population of low-mass stars in local super star clusters for the first time, and to study the environments around these clusters' most massive stars. Webb observations of the massive stars in super star clusters can shed light on how feedback (stellar winds, supernovae and other ejected material) from these stars impacts their surrounding environments and the overall star formation process within their parental clouds.

Image Credit: ESA/Webb, NASA and CSA, M. Zamani (ESA/Webb), M. G. Guarcello (INAF-OAPA) and the EWOCS 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

Galaxy Cluster SPT-CL J0615−5746 as seen by Webb

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An international team of astronomers have used the James Webb Space Telescope to discover gravitationally bound star clusters when the Universe was 460 million years old. This is the first discovery of star clusters in an infant galaxy less than 500 million years after the Big bang.

Young galaxies in the early Universe underwent significant burst phases of star formation, generating substantial amounts of ionising radiation. However, because of their cosmological distances, direct studies of their stellar content have proven challenging. Using Webb, an international team of astronomers have now detected five young massive star clusters in the Cosmic Gems arc (SPT0615-JD1), a strongly-lensed galaxy emitting light when the Universe was roughly 460 million years old, looking back across 97% of cosmic time.

The Cosmic Gems arc was initially discovered in Hubble Space Telescope images obtained by the RELICS (Reionization Lensing Cluster Survey) programme of the lensing galaxy cluster SPT-CL J0615−5746.

With Webb, the science team can now see where stars formed and how they are distributed, in a similar way to how the Hubble Space Telescope is used to study local galaxies. Webb's view provides a unique opportunity to study star formation and the inner workings of infant galaxies at such an unprecedented distance.

Image Credit: ESA/Webb, NASA and CSA, L. Bradley (STScI), A. Adamo (Stockholm University) and the Cosmic Spring collaboration

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

Galaxy Cluster Abell 2390 as seen by Euclid

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Abell 2390 is a galaxy cluster, a giant conglomeration of many galaxies like the Milky Way. More than 50 000 galaxies are seen here, the distances to which can be measured thanks to these new observations. Such clusters contain huge amounts of mass (up to 10 trillion times that of the Sun), with much of this being in the form of dark matter – a form of matter that we can’t observe directly, but is purported to together with dark energy make up the bulk of the contents of the Universe. Galaxy clusters like Abell 2390 are large repositories of dark matter, making them ideal astrophysical laboratories for studying its properties. Once Euclid begins its main survey it will capture many thousands of galaxy clusters over around one-third of the sky, obtaining information we can use to make unprecedented constraints on the dark Universe.

Euclid's new view of the cluster showcases one of the telescope's key techniques for exploring this dark Universe: indirectly measuring the amount and distribution of dark matter in a galaxy cluster via gravitational lensing, a phenomenon where the light travelling to us from more distant galaxies is bent and distorted by this mysterious matter. Thanks to Euclid's advanced instruments we can see an especially beautiful display of lensing in Abell 2390, with multiple giant curved arcs, some of which are actually multiple views of the same distant object.

Alongside understanding more about dark matter, scientists are using Euclid data to measure how the masses and number of galaxy clusters on the sky change over cosmic time, revealing more about the evolution of the Universe (and by extension more about dark energy, which is thought to influence this evolution). Euclid's cutout view of Abell 2390 also shows the faint "intracluster light" emitted by stars that have been ripped away from their parent galaxies into intergalactic space (the light has been enhanced in the cutout image to make it more clearly visible). Viewing this light is a specialty of Euclid, and these stellar orphans may allow us to "see" where dark matter lies.

Euclid captures light ranging from the visible to the near-infrared using its VIS (visible) and NISP (near-infrared) cameras. These can operate simultaneously, imaging wide areas of the sky to create images hundreds of times larger than comparable ones from other space telescopes. This wide field-of-view lets us take pictures of extended objects like Abell 2390 in a single shot, rather than having to take many pictures and stitch them together.

Observing a galaxy cluster in both visible and infrared light allows us to see galaxies at a greater range of distances than using either visible or infrared alone – crucial if we want to observe both the galaxies in a relatively nearby cluster and the galaxies lying behind it (far further from us). Euclid can take these types of deep, wide, high-resolution images hundreds of times faster than other telescopes.

Abell 2390 lies 2.7 billion light-years away in the constellation of Pegasus.

Image Credit: ESA/Euclid/Euclid Consortium/NASA

Image processing: Jean-Charles Cuillandre (CEA Paris-Saclay) and Giovanni Anselmi

Image enhancement: Jean-Baptiste Faure