Star-Forming Region N11 in the LMC

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This Hubble Space Telescope picture features a cloudy starscape from an impressive star cluster. This scene is located in the Large Magellanic Cloud, a dwarf galaxy situated about 160 000 light-years away in the constellations Dorado and Mensa. With a mass equal to 10–20% of the mass of the Milky Way, the Large Magellanic Cloud is the largest of the dozens of small galaxies that orbit our galaxy.

The Large Magellanic Cloud is home to several massive stellar nurseries where gas clouds, like those strewn across this image, coalesce into new stars. This image depicts a portion of the galaxy's second-largest star-forming region, which is called N11. (The most massive and prolific star-forming region in the Large Magellanic Cloud, the Tarantula Nebula, is a frequent target for Hubble.) We see bright, young stars lighting up the gas clouds and sculpting clumps of dust with powerful ultraviolet radiation.

This image marries observations made roughly 20 years apart, a testament to Hubble's longevity. The first set of observations, which were carried out in 2002–2003, capitalised on the exquisite sensitivity and resolution of the then-newly-installed Advanced Camera for Surveys. Astronomers turned Hubble toward the N11 star cluster to do something that had never been done before at the time: catalogue all the stars in a young cluster with masses between 10% of the Sun's mass and 100 times the Sun's mass.

The second set of observations came from Hubble's newest camera, the Wide Field Camera 3. These images focused on the dusty clouds that suffuse the cluster, bringing a new perspective on cosmic dust.

Image Credit: ESA/Hubble and NASA, C. Murray, J. Maíz Apellániz

Image enhancement: Jean-Baptiste Faure

Open Cluster Bochum 14 as imaged by Rubin

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This image shows the open star cluster Bochum 14, captured by the NSF–DOE Vera C. Rubin Observatory. Open clusters like this are made up of stars that formed together from the same cloud of gas and dust, remaining loosely bound as they drift through the Milky Way. Observations like this help astronomers study how stars are born, evolve, and spread out over time. With its powerful wide-field view, the Rubin Observatory is set to reveal countless scenes like this across the southern sky.

Image Credit: RubinObs/NOIRLab/SLAC/NSF/DOE/AURA

Image enhancement: Jean-Baptiste Faure

Open Cluster M21 as seen by Rubin

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Messier 21 or M21, also designated NGC 6531 or Webb's Cross, is an open cluster of stars located to the north-east of Sagittarius in the night sky, close to the Messier objects M20 to M25 (except M24). Here, it is imaged by NSF–DOE Vera C. Rubin Observatory. It was discovered and catalogued by Charles Messier on June 5, 1764. This cluster is relatively young and tightly packed. A few blue giant stars have been identified in the cluster, but Messier 21 is composed mainly of small dim stars. With a magnitude of 6.5, M21 is not visible to the naked eye; however, with the smallest binoculars it can be easily spotted on a dark night. The cluster is positioned near the Trifid Nebula (NGC 6514), but is not associated with that nebulosity. It forms part of the Sagittarius OB1 association.

This cluster is located 1,205 pc away from Earth with an extinction of 0.87. Messier 21 is around 6.6 million years old with a mass of 783.4 M☉. It has a tidal radius of 11.7 pc, with a nucleus radius of 1.6±0.1 pc and a coronal radius of 3.6±0.2 pc. There are at least 105±11 members within the coronal radius down to visual magnitude 15.5, including many early B-type stars. An estimated 40–60 of the observed low-mass members are expected to be pre-main-sequence stars,[8] with 26 candidates identified based upon hydrogen alpha emission and the presence of lithium in the spectrum. The stars in the cluster do not show a significant spread in ages, suggesting that the star formation was triggered all at once.

Image Credit: RubinObs/NOIRLab/SLAC/NSF/DOE/AURA

Image enhancement: Jean-Baptiste Faure

Open Cluster Westerlund 2 as seen by Webb

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This star cluster, known as Westerlund 2, resides in a stellar breeding ground known as Gum 29, located 20,000 light-years away from Earth in the constellation Carina (the Keel).

This image of Westerlund 2 uses data from Webb's Near-InfraRed Camera (NIRCam) and Mid-InfraRed Instrument (MIRI). The cluster measures between 6 light-years and 13 light-years across, and is host to some of our Milky Way galaxy's hottest, brightest, and most massive stars. It was also the feature of Hubble's 25th anniversary image in 2015.

This new Webb image captures the bright, brilliant cluster near the top that is packed with young, massive stars whose intense light shapes the entire scene. Below and around them, swirls of orange and red gas form sculpted walls and tangled clouds – material that is being pushed, eroded, and illuminated by the cluster's powerful radiation. Threaded throughout the view are countless tiny stars just beginning to shine, some still surrounded by the gas and dust from which they formed. The soft blues and pinks are wisps of thinner material drifting between the denser clouds. Scattered across the field are also many bright stars much closer to us, whose sharp, star-shaped patterns are created by Webb's optics. The result is a vivid portrait of a stellar nursery in action, where intense energy from newborn stars carves dramatic shapes into the surrounding nebula and drives the ongoing cycle of star formation.

These new Webb observations of Westerlund 2 have revealed, for the first time, the full population of brown dwarfs in this extremely massive young star cluster, including objects as small as about 10 times the mass of Jupiter. This data is allowing astronomers to find several hundred stars with discs in various evolutionary states to facilitate our understanding of how discs evolve and how planets form in such massive young clusters. This image was developed using data from Webb's programme #3523 (M. Guarcello) as part of the Extended Westerlund 1 and 2 Open Clusters Survey (EWOCS).

Image Credit: ESA/Webb, NASA and CSA, V. Almendros-Abad, M. Guarcello, K. Monsch, and the EWOCS team.

Image enhancement: Jean-Baptiste Faure

The Trifid Nebula as seen by Rubin

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The star-forming Trifid Nebula, also known as Messier 20 (M20), as imaged by NSF–DOE Vera C. Rubin Observatory. The Trifid Nebula is an unusual combination of an open cluster of stars, an emission nebula (the pink region), a reflection nebula (the blue region), and a dark nebula (the dark regions).

Image Credit: RubinObs/NOIRLab/SLAC/NSF/DOE/AURA

Image enhancement: Jean-Baptiste Faure

Trifid and Lagoon Nebulae as seen by Rubin

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In this immense image NSF-DOE Vera C. Rubin Observatory offers a brand new view of two old friends: the Trifid and Lagoon Nebulae. The image provides a demonstration of what makes Rubin unique: its combination of an extremely wide field of view and the speed that allows it to take lots of big images in a very short time. Combining images reveals subtle details in the clouds of gas and dust. The more images we can combine, the more detail we see!

This almost 5-gigapixel image combines 678 exposures taken in just 7.2 hours of observing time, and was composed from about two trillion pixels of data in total. No other observatory is capable of producing an image of such a wide area so quickly and with this much depth.

The Trifid Nebula (also referred to as Messier 20) is a standout in the sky. It's a bright, colorful cloud of gas and dust about 5,000 light-years away in the constellation Sagittarius. What makes it especially striking is the combination of features packed into one place: a glowing pink emission nebula, a cool blue reflection nebula, and dark dust lanes that split it into three sections – hence the name "Trifid". Inside, new stars are forming and blasting out strong winds and radiation, carving up the gas around them. It gives us a dramatic glimpse at how massive stars shape their surroundings even as they're being born.

Below the Trifid Nebula in this image is the Lagoon Nebula (or Messier 8), another vibrant stellar nursery glowing about 4,000 light-years away. You can actually spot the Lagoon with just a pair of binoculars or a small telescope. At its heart is a cluster of young, massive stars – their intense radiation lights up the surrounding gas and shapes the swirling clouds into intricate patterns. The Lagoon nebula provides scientists with a great place to study the earliest stages of star formation – how giant clouds collapse, how star clusters take shape, and how newborn stars start to reshape their environment.

This expansive image of Trifid and Lagoon together exposes an intricate web of dust lanes and star clusters that make this part of the Milky Way come alive with cosmic activity. The exquisite detail in the structure of the nebulosity shown here demonstrates the exceptional quality of Rubin's entire system – from its light-collecting power, to its sensitive camera, to its efficient data transfer and processing system. Over ten years, Rubin Observatory will take millions of images and will image each place in the sky, including this one, about 800 times.

Every time we look at the Universe in a new way, we discover new things we never could have predicted – and with Rubin we will see more than we ever have before.

The image was captured by Rubin Observatory using the 3200-megapixel LSST Camera – the largest digital camera in the world.

Image Credit: RubinObs/NOIRLab/SLAC/NSF/DOE/AURA

Image enhancement: Jean-Baptiste Faure

Emission Nebula and Open Cluster IC 2948

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Exploring the gas cloud known as IC 2948 means finding your way across countless nascent stars born in this enormous stellar nursery. And yet, this is just a snippet of a much larger object: the Running Chicken Nebula. This nebula spans an area on the night sky close to 25 full moons, and yet, the area you see here is not even a third of a full moon. Obtaining such a detailed snippet of the nebula was possible thanks to a 1.5-billion-pixel image taken by the VLT Survey Telescope (VST), hosted and operated by ESO.

Located in the constellation of the Centaur (Centaurus), the Running Chicken Nebula is a labyrinth of gas, dust and young stars whose highly intense radiation erodes away the surrounding material. The gas cloud IC 2948 is the brightest region of the nebula. Here, we find creeping dark clouds, shaped like open hands about to grab their surrounding blooming stars.

First discovered more than a century ago, this gas cloud is helping us understand how stars form and behave during their infancy. To spot IC 2948 within the much larger Running Chicken Nebula, locate the chicken’s rear end (or its head, as some people claim). In your search, you may come across other areas like the stunning GUM 41 nebula.

Image Credit: ESO/VPHAS+ team. Acknowledgement: CASU

Image enhancement: Jean-Baptiste Faure

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

Star-Forming Region NGC 1333 by Webb

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This stunning new mosaic of images from the James Webb Space Telescope showcases the nearby star-forming cluster, NGC 1333. The nebula is in the Perseus molecular cloud, and located approximately 960 light-years away.

Webb's superb sensitivity allows astronomers to investigate young objects with extremely low masses. Some of the faintest "stars" in the picture are in fact newly born free-floating brown dwarfs with masses comparable to those of giant planets.

The same cluster was featured as the 33rd anniversary image of the Hubble Space Telescope in April of 2023. Hubble's image just scratched the surface of this region, because clouds of dust obscure much of the star formation process. Observing with a larger aperture and in the infrared part of the spectrum, Webb is capable of peering through the dusty veil to reveal newborn stars, brown dwarfs and planetary mass objects.

The center of the image presents a deep peek into the heart of the NGC 1333 cloud. Across the image we see large patches of orange, which represent gas glowing in the infrared. These so-called Herbig-Haro objects form when ionised material ejected from young stars collides with the surrounding cloud. They are hallmarks of a very active site of star formation.

Many of the young stars in this image are surrounded by discs of gas and dust, which may eventually produce planetary systems. On the right hand side of the image, we can glimpse the shadow of one of these discs oriented edge-on – two dark cones emanating from opposite sides, seen against a bright background.

Similarly to the young stars in this mosaic, our own Sun and planets formed inside a dusty molecular cloud, 4.6 billion years ago. Our Sun didn't form in isolation but as part of a cluster, which was perhaps even more massive than NGC 1333. The cluster in the mosaic, only 1–3 million years old, presents us with an opportunity to study stars like our Sun, as well as brown dwarfs and free-floating planets, in their nascent stages.

The images were captured as part of the Webb observation programme 1202 (PI: A. Scholz) to survey a large portion of NGC 1333. These data constitute the first deep spectroscopic survey of the young cluster, and have identified brown dwarfs down to planetary masses using the observatory's Near-InfraRed Imager and Slitless Spectrograph (NIRISS). The first results from this survey have been accepted for publication in the Astronomical Journal.

Image Credit: ESA/Webb, NASA and CSA, A. Scholz, K. Muzic, A. Langeveld, R. Jayawardhana

Image enhancement: Jean-Baptiste Faure

Star-Forming Region RCW 106

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The glowing red clouds seen in this picture show dense gas regions where new stars are being born in the RCW 106 region. But only 1% of this gas will actually go on to create stars, and astronomers don’t know why this percentage is so low.

We do know that star formation takes place when regions of these huge clouds of cold gas are able to clump together and eventually collapse into newborn stars, which happens at a critical density. But once we go past that density, do even denser regions produce even more stars, and could this help to explain the 1% mystery?

New results from the Atacama Pathfinder Experiment (APEX), accepted for publication in Astronomy & Astrophysics, suggest this is not the case: denser regions are not more efficient at forming stars. This is perhaps explained by the way these denser clouds fragment into filamentary structures and cores out of which stars will form, but leaves many questions still to be answered. This Picture of the Week highlights these areas of interest. The image imposes a red map of dense gas, imaged with the ArTéMiS camera at APEX, over an optical image taken with the VLT Survey Telescope.

While APEX continues to investigate this stellar mystery, we can expect to see many more stunning images like this.

Image Credit: ESO/M. Mattern et al.

Image enhancement: Jean-Baptiste Faure

30 Doradus: the Tarantula Nebula

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A snapshot of the Tarantula Nebula (also known as 30 Doradus) is the most recent Picture of the Week from the 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 James Webb Space Telescope also recently delved into this region, revealing thousands of never-before-seen young stars.

This new image combines data from two different observing proposals. The first was designed to explore the properties of the dust grains that exist in the void between stars and which make up the dark clouds winding through this image. This proposal, which astronomers named Scylla, complements another Hubble observing proposal called Ulysses and is revealing how interstellar dust interacts with starlight in a variety of environments. This image also incorporates data from an observing programme studying star formation in conditions similar to the early Universe, as well as cataloguing the stars of the Tarantula Nebula for future science with Webb.

Image Credit: ESA/Hubble and NASA, C. Murray, E. Sabbi

Acknowledgement: Y.-H. Chu

Image enhancement: Jean-Baptiste Faure

Star-Forming Region NGC 346 by Webb

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This image features NGC 346, one of the most dynamic star-forming regions in nearby galaxies, as seen by the James Webb Space Telescope. NCG 346 is located in the Small Magellanic Cloud (SMC), a dwarf galaxy close to our Milky Way.

The star forming region sweeps across the scene, dominated by hues of purple. Tones of yellow outline the region's irregular shape. Many bright stars dominate the scne, as well as countless smaller stars the scatter the image's background.

Image Credit: NASA, ESA, CSA, STScI, A. Pagan (STScI)

Image enhancement: Jean-Baptiste Faure

The Tarantula Nebula as seen by Webb

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In this mosaic image stretching 340 light-years across, Webb's Near-Infrared Camera (NIRCam) displays the Tarantula Nebula star-forming region in a new light, including tens of thousands of never-before-seen young stars that were previously shrouded in cosmic dust. The most active region appears to sparkle with massive young stars, appearing pale blue. Scattered among them are still-embedded stars, appearing red, yet to emerge from the dusty cocoon of the nebula. NIRCam is able to detect these dust-enshrouded stars thanks to its unprecedented resolution at near-infrared wavelengths.

To the upper left of the cluster of young stars, and the top of the nebula's cavity, an older star prominently displays NIRCam's distinctive eight diffraction spikes, an artefact of the telescope's structure. Following the top central spike of this star upward, it almost points to a distinctive bubble in the cloud. Young stars still surrounded by dusty material are blowing this bubble, beginning to carve out their own cavity. Astronomers used two of Webb’s spectrographs to take a closer look at this region and determine the chemical makeup of the star and its surrounding gas. This spectral information will tell astronomers about the age of the nebula and how many generations of star birth it has seen.

Farther from the core region of hot young stars, cooler gas takes on a rust colour, telling astronomers that the nebula is rich with complex hydrocarbons. This dense gas is the material that will form future stars. As winds from the massive stars sweep away gas and dust, some of it will pile up and, with gravity's help, form new stars.

Image Credit: NASA, ESA, CSA, and STScI

Image enhancement: Jean-Baptiste Faure

Open Cluster NGC 1755

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The open star cluster NGC 1755 resembles a pinch of salt strewn on a jet-black tablecloth in this image from the Hubble Space Telescope. This collection of stars resides in one the Milky Way's near neighbours – the Large Magellanic Cloud – and measures 120 light-years from side to side. Despite this impressive breadth, NGC 1755 is a member of the smaller class of star clusters. Star clusters are gravitationally bound collections of stars, and come in two main varieties – smaller open clusters like NGC 1755, which are hosts to younger stars, and gargantuan globular clusters, which can contain millions of older stars.

Hubble gazed into the heart of NGC 1755 in order to better understand how different populations of stars can co-exist in a single cluster. A population of stars is a group of stars with similar properties such as age or chemical composition, and these populations provide astronomers with valuable insights into the births, lives, and deaths of stars. Clusters in the Magellanic Clouds are particularly useful natural laboratories thanks to the Clouds' proximity to the Milky Way. Hubbles's eagle-eyed vision was a vital asset when observing NGC 1755 – with so many stars packed into a small area of sky, Hubble's high-resolution Advanced Camera for Surveys and Wide Field Camera 3 allowed individual stars in the cluster to be distinguished.

Image Credit: ESA/Hubble and NASA, A. Milone, G. Gilmore

Image enhancement: Jean-Baptiste Faure

Open Cluster NGC 2164

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This picture shows an open cluster known as NGC 2164, which was first discovered in 1826 by a Scottish astronomer named James Dunlop. NGC 2164 is located within one of the Milky Way galaxy's closest neighbours – the satellite galaxy known as the Large Magellanic Cloud. The Large Magellanic cloud is a relatively small galaxy that lies about 160 000 light-years from Earth. It is considered a satellite galaxy because it is gravitationally bound to the Milky Way. In fact, the Large Magellanic cloud is on a very slow collision course with the Milky Way – it's predicted that they will collide 2.4 billion years from now.

The Large Magellanic Cloud only contains about one hundredth as much mass as the Milky Way, but it still contains billions of stars. The open cluster NGC 2164 is in good company in the Large Magellanic Cloud – the satellite galaxy is home to roughly 700 open clusters, alongside about 60 globular clusters. This image of NGC 2164 was taken by the NASA/ESA Hubble Space Telescope's Wide Field Camera 3 (WFC3), which has previously imaged many other open clusters, including NGC 330 and Messier 11.

Image Credit: ESA/Hubble and NASA, J. Kalirai, A. Milone

Image enhancement: Jean-Baptiste Faure

Open Cluster NGC 330

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This picture 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. The criss-cross patterns surrounding the stars in this image – known as diffraction spikes – were created when starlight interacted with the four thin vanes supporting Hubble's secondary mirror.

As star clusters form from a single primordial cloud of gas and dust, all the stars they contain are roughly the same age. This makes them useful natural laboratories for astronomers to learn how stars form and evolve. This image uses observations from Hubble’s Wide Field Camera 3, and incorporates data from two very different astronomical investigations. The first aimed to understand why stars in star clusters appear to evolve differently from stars elsewhere, a peculiarity first observed by the Hubble Space Telescope. The second aimed to determine how large stars can be before they become doomed to end their lives in cataclysmic supernova explosions.

Image Credit: ESA/Hubble and NASA, J. Kalirai, A. Milone

Image enhancement: Jean-Baptiste Faure

The Trapezium Cluster in M42

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The Orion Nebula is arguably the finest of all nebulae within the Milky Way visible from the Northern Hemisphere. With a gaseous repository of 10 000 suns, and illuminated by a cluster of hot young stars, the clouds of Messier 42 (M42) – as it is also known – glow with fantastic colours and shapes, giving us a bird's eye view of one of the greatest star forming nurseries in our part of the Milky Way. M42 is a complex of glowing gas, mostly hydrogen but also helium, carbon, nitrogen, and oxygen in decreasing amounts, located 1 500 light-years away.

At its very heart, we find the Trapezium, a group of four very hot stars that illuminate the nebula. They are the brightest of an extended cluster of several thousand young stars many of which lie unseen within the opaque gas and dust. Amazingly, whilst the Orion Nebula is easy to identify with the unaided eye, there is apparently no written record of its existence before the 17th century.

This image is based on data acquired with the 1.5 m Danish telescope at the ESO La Silla Observatory in Chile, through three filters (B: 60 s, V: 30 s, R: 21 s). East is at the upper right corner and North is at the lower right.

Image Credit: ESO/IDA/Danish 1.5 m/R.Gendler, J.-E. Ovaldsen, and A. Hornstrup

Image enhancement: Jean-Baptiste Faure

The Quintuplet Cluster near the Galaxy's Center

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Although this cluster of stars gained its name due to its five brightest stars, it is home to hundreds more. The huge number of massive young stars in the cluster is clearly captured in this Hubble Space Telescope image.

The cluster is located close to the Arches Cluster and is just 100 light-years from the center of our galaxy. The cluster's proximity to the dust at the center of the galaxy means that much of its visible light is blocked, which helped to keep the cluster unknown until its discovery in 1990, when it was revealed by observations in the infrared. Infrared images of the cluster, like the one shown here, allow us to see through the obscuring dust to the hot stars in the cluster.

The Quintuplet Cluster hosts two extremely rare luminous blue variable stars: the Pistol Star and the lesser known V4650 Sgr. If you were to draw a line horizontally through the center of this image from left to right, you could see the Pistol Star hovering just above the line about one third of the way along it. The Pistol Star is one of the most luminous known stars in the Milky Way and takes its name from the shape of the Pistol Nebula that it illuminates, but which is not visible in this infrared image. The exact age and future of the Pistol Star are uncertain, but it is expected to end in a supernova or even a hypernova in one to three million years.

The cluster also contains a number of red supergiants. These stars are among the largest in the galaxy and are burning their fuel at an incredible speed, meaning they will have a very short lifetime. Their presence suggests an average cluster age of nearly four million years. At the moment these stars are on the verge of exploding as supernovae. During their spectacular deaths they will release vast amounts of energy which, in turn, will heat the material – dust and gas – between the other stars.

Image Credit: ESA/Hubble and NASA

Image enhancement: Jean-Baptiste Faure

Open Cluster Cep OB 3b

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Cep OB 3b is rich young cluster located in the northern constellation of Cepheus. This image was created by combining individual images observed through four different filters on the 0.9 meter telescope at Kitt Peak: blue, visual (cyan), near infrared (orange) and an emission line of hydrogen (red). The brightest yellow star near the center of the image is a foreground star, lying between us and the young cluster. The other bright stars are the massive young stars of the cluster that are heating the gas and dust in the cloud and blowing out cavities. Surrounding these massive cluster stars are thousands of smaller young stars that may be in the process of forming planetary systems.

Image Credit: T.A. Rector (University of Alaska Anchorage), T. Allen (University of Toledo) and WIYN/NOIRLab/NSF/AURA

Image enhancement: Jean-Baptiste Faure