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

Lenticular Galaxy NGC 7722

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For this picture from the Hubble Space Telescope, we have a sight of an uncommon galaxy with a striking appearance. This is NGC 7722, a lenticular galaxy located about 187 million light-years away in the constellation Pegasus.

A "lenticular", meaning "lens-shaped", galaxy is a type that sits in between the more familiar spiral galaxies and elliptical galaxies. It is also less common than these – partly because when a galaxy has an ambiguous appearance, it can be hard to determine if it is actually a spiral, actually an elliptical galaxy, or something in between. Many of the known lenticular galaxies sport features of both spiral and elliptical galaxies. In this case, NGC 7722 lacks the defined arms of a spiral galaxy, while it has an extended, glowing halo and a bright bulge in the center similar to an elliptical galaxy. Unlike elliptical galaxies, it has a visible disc – concentric rings swirl around its bright nucleus. Its most prominent feature, however, is undoubtedly the long lanes of dark red dust coiling around the outer disc and halo.

This new Hubble image, the sharpest yet taken of NGC 7722, brings the impressive dust lanes into sharp focus. Bands of dust like this are not uncommon in lenticular galaxies, and they stand out against the broad, smooth halo of light that typically surrounds lenticular galaxies. The distinctive dust lanes of NGC 7722 are thought to result from a merger with another galaxy in the past, similar to other lenticular galaxies. It is not yet fully understood how lenticular galaxies form, but mergers and other gravitational interactions are thought to play an important part, reshaping galaxies and exhausting their supplies of gas while bringing new dust.

While it doesn't host as many new, young stars as a spiral galaxy, there's still activity in NGC 7722: in 2020 it was host to the explosion of a star that could be detected from Earth. SN 2020SSF was a Type Ia supernova, an event which occurs when a white dwarf star in a binary system siphons enough mass away from its companion star that it grows unstable and explodes. These explosions output a remarkably consistent level of light: by measuring how bright they appear from Earth and comparing against how bright they really are, it's possible to tell how far away they must be. Type Ia supernovae are one of the best ways to measure distances to galaxies, so understanding exactly how they work is of great importance to astronomers.

Taken with Hubble's Wide Field Camera 3, this Hubble image was obtained as part of an observing programme (#16691, PI: R. J. Foley) that followed up on recent supernovae. SN 2020SSF is not visible in this image, as it was actually taken two years later, when the supernova had long faded. This was on purpose: the aim of the observations was to witness the aftereffects of the supernova and examine its surroundings, which can only be done once the intense light of the explosion is gone. With Hubble's clear vision, astronomers can search for radioactive material created by the supernova, catalogue its neighbours to see how old the star likely was, and look for the companion star it left behind – all from almost 200 million light-years away.

Image Credit: ESA/Hubble and NASA, R. J. Foley (UC Santa Cruz), Dark Energy Survey/DOE/FNAL/DECam/CTIO/NOIRLab/NSF/AURA

Acknowledgement: Mehmet Yüksek

Image enhancement: Jean-Baptiste Faure

Planetary Nebula PMR 1 as seen by Webb

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Two heads are better than one in the latest images from NASA's James Webb Space Telescope, which reveal new detail in a mysterious, little-studied nebula surrounding a dying star.

Nebula PMR 1 is a cloud of gas and dust that bears an uncanny resemblance to a brain in a transparent skull, inspiring its nickname, the "Exposed Cranium" nebula. Webb captured its unusual features in both near- and mid-infrared light. The nebula was first revealed in infrared light by a predecessor to Webb, NASA's now-retired Spitzer Space Telescope, more than a decade ago. Webb's advanced instruments show detail that enhances the nebula's brain-like appearance.

The nebula appears to have distinct regions that capture different phases of its evolution – an outer shell of gas that was blown off first and consists mostly of hydrogen, and an inner cloud with more structure that contains a mix of different gases. Both Webb's NIRCam (Near-Infrared Camera) and MIRI (Mid-Infrared Instrument) show a distinctive dark lane running vertically through the middle of the nebula that defines its brain-like look of left and right hemispheres. Webb's resolution shows that this lane could be related to an outburst or outflow from the central star, which typically occurs as twin jets burst out in opposite directions. Evidence for this is particularly notable at the top of the nebula in Webb’s MIRI image, where it looks like the inner gas is being ejected outward.

While there is still much to be understood about this nebula, it's clear that it is being created by a star near the end of its fuel-burning "life". In their end stages, stars expel their outer layers. It's a dynamic and fairly fast process, in cosmic terms. Webb has captured a moment in this star's decline. What ultimately happens will depend on the mass of the star, which is yet to be determined. If it's massive enough, it will explode in a supernova. A less massive Sun-like star will continue to shed layers until only its core remains as a dense white dwarf, which will cool off over eons.

Image Credit: NASA, ESA, CSA, STScI, Image Processing: Joseph DePasquale (STScI)

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

Star-Forming Region Sagittarius B2 by Webb

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Stars, gas and cosmic dust in the Sagittarius B2 molecular cloud glow in near-infrared light, captured by Webb's NIRCam (Near-Infrared Camera). In this light, astronomers see more of the region's diverse, colourful stars, but less of its gas and dust structure. Webb's instruments each provide astronomers with important information that help build a more complete picture of what is happening in this intriguing portion of the centre of our galaxy.

Sagittarius B2 is the Milky Way galaxy's most massive and active star forming cloud, producing half of the stars created in the galactic center region despite having only 10 percent of the area's star-making material. Now, Webb has revealed stunning new views of the region, using both its near-infrared and mid-infrared instruments, to capture both its colourful stars and gaseous stellar nurseries in unprecedented detail.

Sagittarius B2 is located only a few hundred light-years from the supermassive black hole at the heart of the galaxy called Sagittarius A, a region densely packed with stars, star-forming clouds, and complex magnetic fields. The infrared light that Webb detects is able to pass through some of the area's thick clouds to reveal young stars and the warm dust surrounding them. Astronomers think that analysis of Webb's data will help unravel enduring mysteries of the star formation process, and why Sagittarius B2 is forming so many more stars than the rest of the galactic center.

However, one of the most notable aspects of Webb's images of Sagittarius B2 are the portions that remain dark. These ironically empty-looking areas of space are actually so dense with gas and dust that even Webb cannot see through them. These thick clouds are the raw material of future stars and a cocoon for those still too young to shine.

Image Credit: NASA, ESA, CSA, STScI, A. Ginsburg (University of Florida); Image Processing: A. Pagan (STScI)

Image enhancement: Jean-Baptiste Faure

Galaxy Cluster Abell S1063 as seen by Webb

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The eye is first drawn, in this James Webb Space Telescope picture, to the central mega-monster that is galaxy cluster Abell S1063. This behemoth collection of galaxies, lying 4.5 billion light-years from Earth in the constellation Grus (the Crane), dominates the scene. Looking more closely, this dense collection of heavy galaxies is surrounded by glowing streaks of light, and these warped arcs are the true object of scientists’ interest: faint galaxies from the Universe's distant past.

Abell S1063 was previously observed by the Hubble Space Telescope's Frontier Fields programme. It is a strong gravitational lens: the galaxy cluster is so massive that the light of distant galaxies aligned behind it is bent around it, creating the warped arcs that we see here. Like a glass lens, it focuses the light from these faraway galaxies. The resulting images, albeit distorted, are both bright and magnified — enough to be observed and studied. This was the aim of Hubble’s observations, using the galaxy cluster as a magnifying glass to investigate the early Universe.

The new imagery from Webb's Near-Infrared Camera (NIRCam) takes this quest even further back in time. This image showcases an incredible forest of lensing arcs around Abell S1063, which reveal distorted background galaxies at a range of cosmic distances, along with a multitude of faint galaxies and previously unseen features.

This image is what's known as a deep field – a long exposure of a single area of the sky, collecting as much light as possible to draw out the most faint and distant galaxies that don't appear in ordinary images. With 9 separate snapshots of different near-infrared wavelengths of light, totalling around 120 hours of observing time and aided by the magnifying effect of gravitational lensing, this is Webb's deepest gaze on a single target to date. Focusing such observing power on a massive gravitational lens, like Abell S1063, therefore has the potential to reveal some of the very first galaxies formed in the early Universe.

The observing programme that produced this data, GLIMPSE, aims to probe the period known as Cosmic Dawn, when the Universe was only a few million years old. Studying the galaxies revealed by gravitational lensing has the potential to develop our understanding of the emergence of the first galaxies. Analysis of this NIRCam data by the GLIMPSE team has already produced candidates for galaxies that existed as early as 200 million years after the Big Bang, and hints of the elusive first population of stars in the Universe.

Image Credit: ESA/Webb, NASA and CSA, H. Atek, M. Zamani (ESA/Webb)

Acknowledgement: R. Endsley

Image enhancement: Jean-Baptiste Faure