Using two X-ray space telescopes, astronomers now think they have detected evidence of a supernova remnant very close to the center of the Milky Way.
You can read their paper here [pdf]. The image to the right is a composite of optical (the stars), radio (the red nebula), and Chanda’s X-ray data (the blue nebula). From the press release:
The evidence for the new supernova remnant, located about 26,000 light-years from Earth, comes from X-ray data from Chandra and XMM-Newton. The X-ray data reveals a “blob” of X-ray emission [indicated by blue] that may come from the remains of a massive star that self-destructed as a supernova, buried within the larger cloud of expanding gas.
The location of this suspected supernova remnant in the image is [that blue region]. It is in bubble of gas [the surrounding larger and smaller red objects] that has had electrons stripped away from hydrogen — called an “H II region” — surrounding a massive, young star. If this is indeed a supernova remnant, then it is expanding at about two million miles per hour and is at least about 1,700 years old.
,..The long filaments seen in the radio image are caused by energetic particles travelling along magnetic fields that are mostly directed perpendicular to the plane of the galaxy.
According to the paper, this supernova remnant is found on the western edge of a vast energized gas cloud called the Central Molecular Zone (CMZ), 1,600 to 1,900 light years across, that spans the Milky Way’s center. The features seen in the image above are part of a feature on the CMZ’s western edge called Sagittarius C, which apparently has not been studied as much as other parts of the CMZ.
Time for another cool image. The picture to the right, cropped and reduced to post here, was released today by the science team of the 8.1 meter Gemini North telescope on Mauna Kea in Hawaii. It provides a close-up view of the central blob that forms NGC 1514, a planetary nebula located about 1,500 light years away and nicknamed the Crystal Ball Nebula by Gemini’s PR team.
They might think it resembles a crystal ball, but to my eye this is an amoeba undulating in weightlessness.
Planetary nebulae form when a low- or intermediate-mass star ejects its outer layers near the end of its life, forming a somewhat spherical cloud of gas. They typically have smoother, spherical shapes, making the Crystal Ball Nebula unique for its bumpy shells of gas. As the central star casts away this gas, its inner core is exposed. Radiation from the core energizes the gas, giving it a scorching temperature and chromatic glow. The Crystal Ball Nebula, for example, has an estimated temperature of 15,000 K.
…While it may appear in this image as if there is a single shining light source at the heart of the Crystal Ball Nebula, as Herschel saw, it actually contains two stars. These two stars orbit each other with a period of around nine years — the longest known for any binary pair within a planetary nebula. Scientists believe that one of these stars, which was once several times more massive than our Sun, released its outer layers while in the throes of death. As the progenitor star and its binary companion orbit each other, they mold the expanding shell of gas with their strong, asymmetrical winds, forming the lumpy layers we see today.
The analogy I like to use for this process is that of a blender. The two stars act like the blender’s blades, mixing the outflowing gas from the stars into these spectacular shapes.
The 8.1-meter Gemini North telescope, located on the summit of Maunakea in Hawai‘i, has captured NGC 1514, nicknamed the Crystal Ball Nebula, in awe-inspiring detail. This nebula, with its mesmerizing glow of gas, harbors hints of a past stellar death, and its asymmetrical shell is now being shaped by the binary pair that lies at its center. Gemini North is one half of the International Gemini Observatory, partly funded by the U.S. National Science Foundation (NSF) and operated by NSF NOIRLab.
Cool image time! The picture to the right, cropped to post here, was taken by the Hubble Space Telescope and released today. It shows a small section of the Trifid Nebula, located about 5,000 light years away.
This location has been imaged numerous times in the past by Hubble. The area shown illustrates some fundamental aspects of stellar and nebula formation. The dark area in the lower right is a thick dust cloud. Several energetic O and B supermassive stars are out of view at the top. The radiation from these stars (indicated by the blue), is hitting that dust cloud and literally destroying it. It appears that the foreground “horn” exists because a larger object is blocking the radiation, allowing dust to survive in the background.
I have no explanation for the background “horn”.
This new image was taken in parallel with an image of the entire Trifid Nebula, taken by the new Rubin Telescope in Chile. Though Rubin cannot see with the same resolution as Hubble, its image is quite worthwhile viewing.
The colours in this image from the NASA/ESA Hubble Space Telescope tell a story about density in the Trifid Nebula, a star-forming region about 5000 light-years from Earth. The top left, where it is bright blue, has the smallest amount of dust. Here, powerful ultraviolet light stripped electrons from nearby gas, creating a glow, with winds creating a bubble by clearing out surrounding dust. An example of active cloud destruction is toward the top of the head-shaped area with two “horns.” Bright yellow gas streams upward where gas and dust are being destroyed. Thicker dust appears dark brown, like mud. In the far-right corner, which is nearly pitch black, the dust is the densest. Fully formed stars (bright orange orbs) are scattered across the scene. Their light and stellar winds have also cleared the immediate areas around them. Over millions of years, the gas and dust that make up this nebula (also known as Messier 20 or M20) will disappear and only stars will remain. [Image description: A tightly cropped Hubble view of a vast star-forming region known as the Trifid Nebula. The top left is bright blue. Brown and amber colours run from top right through the center in irregular, overlapping lines to the bottom-center. At bottom right, the view is almost black. Tiny, amber-coloured stars appear throughout the scene. Toward the left there is a prominent brown shape that looks like a head with two horns. The left horn points left and is wavy. The right horn is triangular and points up. The brown dust continues, flowing down, as if along a back, and up toward the top right. A prominent line, about the same length as the left horn, appears below the middle of the body, and changes from orange to red. A small, separate semi-transparent pillar is left of the head. A few slightly larger, blue foreground stars with four diffraction spikes appear in the bottom half.]
Using the Hubble Space Telescope, astronomers have obtained a new high resolution image of the Crab Nebula, and by comparing it with earlier Hubble images taken in 1999/2000 have been able to track the continuing expansion and evolution of this supernova remnant over a period now covering almost a quarter century.
The supernova itself became visible on Earth in 1054, though it actually erupted about 6,500 years earlier, as the Crab Nebula is 6,500 light years away. In the 25 years Hubble has been tracking the remnant’s expansion astronomers estimate it is expanding at about 3.4 million miles per hour.
[William Blair of Johns Hopkins University] noted that filaments around the periphery of the nebula appear to have moved more compared to those in the center, and that rather than stretching out over time, they appear to have simply moved outward. This is due to the nature of the Crab as a pulsar wind nebula powered by synchrotron radiation, which is created by the interaction between the pulsar’s magnetic field and the nebula’s material. In other well-known supernova remnants, the expansion is instead driven by shockwaves from the initial explosion, eroding surrounding shells of gas that the dying star previously cast off.
The new, higher-resolution Hubble observations are also providing additional insights into the 3D structure of the Crab Nebula, which can be difficult to determine from a 2D image, Blair said. Shadows of some of the filaments can be seen cast onto the haze of synchrotron radiation in the nebula’s interior. Counterintuitively, some of the brighter filaments in the latest Hubble images show no shadows, indicating they must be located on the far side of the nebula.
A movie showing the changes between these two images can be seen here. It is worth your while to take a look. These optical images will be further enhanced as the Webb Space Telescope gathers infrared data.
Cool image time! The two false-color pictures to the right, reduced to post here, were taken by two different infrared cameras on the Webb Space Telescope.
The object, PMR-1, is about 5,000 light years away and has apparently not been studied very much in the past. In 2013 astronomers used the Spitzer Space Telescope to get a first look in the infrared, at a much lower resolution. They also gave this object a nickname, the “Exposed Cranium” nebula. From the Webb press release:
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.
The dark lane suggests we are looking at the star’s equator, with the two lobes on either side the material being flung out ward from the poles. It is also possible this is wrong, because the lobes on either side do not have a clear distinct jet-like appearance.
Astronomers using both NASA’s long established Hubble Space Telescope and Europe’s new Euclid space telescope have produced new optical/infrared images of the Cat’s Eye planetary nebula.
Those images are to the right, cropped, reduced, and sharpened to post here. The Hubble image at bottom shows the complex structure of the nebula itself, located about 4,400 light years away and believed created by the inner orbital motions of a binary star system that act almost like the blades in a blender, mixing the material thrown off by one or both of the stars as they erupt in their latter stages of life.
In Euclid’s wide, near-infrared, and visible light view, the arcs and filaments of the nebula’s bright central region are situated within a halo of colorful fragments of gas zooming away from the star. This ring was ejected from the star at an earlier stage, before the main nebula at the center formed. The whole nebula stands out against a backdrop teeming with distant galaxies, demonstrating how local astrophysical beauty and the farthest reaches of the cosmos can be seen together with Euclid.
Euclid has a primary mirror 1.2 meters in diameter, about half that of Hubble. Though it can’t zoom in with the same resolution, its view is as sharp since it is in space above the atmosphere. It thus provides a wider view, which in this case helps provide a larger context to the detailed close-up view provided by Hubble.
In many ways Euclid is Hubble’s replacement, produced by the European Space Agency, as NASA and the American astronomy community has not been able to get together to build their own new optical orbiting telescope.
Cool image time! The picture to the right, reduced to post here, was taken by the Hubble Space Telescope as part of a study of “preplanetary nebula,” the initial stages of a planetary nebula that forms as some star types begin dying. From the caption:
Many preplanetary nebulae are relatively dim and hard to spot. They are made of layers of gas ejected by the star, but that star is not yet hot enough to ionise the gas and cause it to glow. The Egg Nebula is relatively unique, easily visible as a sparkling jewelled egg in space. Powerful beams of starlight blast out of the inner cloud, two a-side, giving a breathtaking illumination to this cosmic structure. Fast-moving outflows of hot molecular hydrogen also emerge from within the dust cloud, visible just at the base of the searchlight beams. These outflows glow with infrared light, which is shown in this image by orange highlights.
The central cloud of dust is surrounded by concentric rings, themselves made up from thin, faint arcs of gas. These were created by successive outbursts from the central star, which ejected a little more material from its outer surface every few hundred years. The beams of starlight are reflected by these layers of gas, creating an appearance like ripples on the surface of water. The way that gas molecules reflect and scatter light gives a bluish colour to the arcs. The reflected starlight reveals important details about the central star, which is impossible to view directly in its dusty shell.
Many planetary nebula get their spectacular shapes because they have a binary star system in their center, that act like the blades in a blender as they circle each other, mixing the materials the stars’ eject to form those shapes. Because of those surrounding shells, it is often impossible to determine with the nebula has a single central star, or a binary system.
This newly processed image from the NASA/ESA Hubble Space Telescope is the clearest view yet of the Egg Nebula. It is a preplanetary nebula, a structure of gas and dust created as a Sun-like star approaches the end of its life. The Egg that we see now will eventually hatch, revealing a white dwarf at its centre and leaving its shell to become a spectacular planetary nebula. Many preplanetary nebulae are relatively dim and hard to spot. They are made of layers of gas ejected by the star, but that star is not yet hot enough to ionise the gas and cause it to glow. The Egg Nebula is relatively unique, easily visible as a sparkling jewelled egg in space. Powerful beams of starlight blast out of the inner cloud, two a-side, giving a breathtaking illumination to this cosmic structure. Fast-moving outflows of hot molecular hydrogen also emerge from within the dust cloud, visible just at the base of the searchlight beams. These outflows glow with infrared light, which is shown in this image by orange highlights. The central cloud of dust is surrounded by concentric rings, themselves made up from thin, faint arcs of gas. These were created by successive outbursts from the central star, which ejected a little more material from its outer surface every few hundred years. The beams of starlight are reflected by these layers of gas, creating an appearance like ripples on the surface of water. The way that gas molecules reflect and scatter light gives a bluish colour to the arcs. The reflected starlight reveals important details about the central star, which is impossible to view directly in its dusty shell. [Image description: In the centre an opaque cloud of grey gas hides a star. Two strong beams of light from the star emerge from large holes in both sides of the cloud. The central cloud is surrounded by concentric, wispy shells of gas, illuminated by the star’s light. The shells reflect extra light where they’re hit by the twin beams. A crowd of smaller stars with cross-shaped spikes over them surround the nebula on a black background.]
Composite image showing iron bar inside Ring Nebula.
Click for original.
The uncertainty of science: Using a new instrument on the Herschel Telescope in Chile, astronomers have detected a bar of iron cutting across the hole in the center of the Ring Nebula. You can read their paper here.
The cloud of iron atoms, described for the first time in Monthly Notices of the Royal Astronomical Society, is in the shape of a bar or strip: it just fits inside the inner layer of the elliptically shaped nebula, familiar from many images including those obtained by the James Webb Space Telescope at infrared wavelengths. The bar’s length is roughly 500 times that of Pluto’s orbit around the Sun and, according to the team, its mass of iron atoms is comparable to the mass of Mars.
The bar does not cross the nebula’s central star, nor does it exhibit the kind of motion seen by jets flowing outward from such stars. From the paper’s conclusion:
At present, there seem to be no obvious explanations that can account for the presence of the narrow ‘bar’ of [Fe v] and [Fe vi] emission seen in our WEAVE spectra to extend across the central regions of the Ring Nebula. Fresh observations of this newly uncovered feature at much higher spectral resolution seem essential to make progress
The scientists toss out the possibility that the bar is the remains of a rocky planet vaporized at some point in the system’s past, but that is simply a wild guess.
Courtesy of BtB’s stringer Jay. This post is also an open thread. I welcome my readers to post any comments or additional links relating to any space issues, even if unrelated to the links below.
Astronomers detect a three-galaxy merger, the third ever discovered
The headline at the link is utter garbage, designed as clickbait. The headline I have given you describes the story’s text accurately. One other detail: All three galaxies also appear to have active nuclei, suggesting the presence of supermassive black holes.
Cool image time! The picture to the right, reduced and sharpened to post here, was taken by the Hubble Space Telescope back in 2017 but released this week by NASA’s PR department. It shows what astronomers have nicknamed the Calabash Nebula. From the Wikipedia page:
The Calabash Nebula, also known as the Rotten Egg Nebula or by its technical name OH 231.84 +4.22, is a protoplanetary nebula (PPN) 1.4 light years (13 Pm) long and located some 5,000 light years (47 Em) from Earth in the constellation Puppis. The name “Calabash Nebula” was first proposed in 1989 in an early paper on its expected nebular dynamics, based on the nebula’s appearance.[5] The Calabash is almost certainly a member of the open cluster Messier 46, as it has the same distance, radial velocity, and proper motion.[6] The central star is QX Puppis, a binary composed of a very cool Mira variable and an A-type main-sequence star.
The star in the center is an ancient red giant that is in the initial stages of dying. As it does so it periodically erupts, sending out jets of material from its poles. The result is this elongated shape. According to the release, “the gas shown in yellow is moving close to a million kilometers an hour.”
Over the next few thousand years these eruptions will shape the planetary nebula. Since the central star is actually a binary, those two stars will likely act like the blades in a mixer, adding more interesting forms to the material as it is shot out to form this nebula.
The Calabash Nebula, pictured here — which has the technical name OH 231.8+04.2 — is a spectacular example of the death of a low-mass star like the Sun. This image taken by the NASA/ESA Hubble Space Telescope shows the star going through a rapid transformation from a red giant to a planetary nebula, during which it blows its outer layers of gas and dust out into the surrounding space. The recently ejected material is spat out in opposite directions with immense speed — the gas shown in yellow is moving close to a million kilometres an hour. Astronomers rarely capture a star in this phase of its evolution because it occurs within the blink of an eye — in astronomical terms. Over the next thousand years the nebula is expected to evolve into a fully fledged planetary nebula. The nebula is also known as the Rotten Egg Nebula because it contains a lot of sulphur, an element that, when combined with other elements, smells like a rotten egg — but luckily, it resides over 5000 light-years away in the constellation of Puppis (The Poop deck).
Today’s ESA/Hubble Picture of the Week features the spiral galaxy NGC 4535, which is situated about 50 million light-years away in the constellation Virgo (The Maiden). This galaxy has been nicknamed the ‘Lost Galaxy’ because it’s extremely faint when viewed through a small telescope. With a mirror spanning 2.4 metres across, Hubble is well equipped to observe dim galaxies like NGC 4535 and pick out features like its massive spiral arms and central bar of stars. On full display in this Hubble image are NGC 4535’s young star clusters, which dot the galaxy’s spiral arms. Many of the groupings of bright blue stars are enclosed by glowing pink clouds. These clouds, called H II (‘H-two’) regions, are a sign that the galaxy is home to especially young, hot, and massive stars that are blazing with high-energy radiation. By heating the clouds in which they were born, shooting out powerful stellar winds, and eventually exploding as supernovae, massive stars certainly shake up their surroundings. This Hubble image incorporates data from an observing programme that will catalogue roughly 50 000 H II regions in nearby star-forming galaxies like NGC 4535. A previous image of NGC 4535 was released in 2021. Both the 2021 image and today’s image incorporate observations from the PHANGS programme, which seeks to understand the connections between young stars and cold gas. Today’s image adds a new dimension to our understanding of NGC 4535 by capturing the brilliant red glow of the nebulae that encircle massive stars in their first few million years of life. [Image Description: A close-in view of a spiral galaxy that faces the viewer. Brightly lit spiral arms swing outwards through the galaxy’s disc, starting from an elliptical region in the centre. Thick strands of dark reddish dust are spread across the disc, mostly following the spiral arms. The arms also contain many glowing pink-red spots where stars form. The galaxy is a bit fainter beyond the arms, but speckled with blue stars.]
Click for full graphic. CSM stands for the
circumstellar matter that surrounded the star
prior to eruption.
Using the Very Large Telescope in Chile, astronomers were able to observe a supernova in its very earliest moments after eruption, the earliest yet, and determined the eruption did not flow outward in all directions, but appeared to be bi-polar, as indicated by the cartoon to the right.
To capture the snapshot of the April 2024 supernova, astronomers used the European Southern Observatory’s Very Large Telescope in Chile, which was able to look at the polarization, or orientation, of the supernova’s light. Using a technique called spectropolarimetry, the researchers used the light’s polarization to re-create the explosion’s shape in its first moments. Their results showed that the light emanated not uniformly, like the light from a typical star, but elongated, shaped like an olive.
You can read their paper here. The cartoon comes from Figure 4, and is their “most plausible” interpretation of the data.
This bi-polar shape suggests that in the initial stages of the eruption the material shot out the star’s poles, as seen routinely in planetary nebulae as well as other eruptive stars like Eta Carina. The data also suggests the initial explosion was shaped by the circumstellar material surrounding the star. Such material tends to concentrate at a star’s ecliptic, like our solar system, With less material at the poles, the initial blast favored those directions.
Theorists will now use this data point to better refine the models that attempt to explain how supernovae explode.
Courtesy of BtB’s stringer Jay. This post is also an open thread. I welcome my readers to post any comments or additional links relating to any space issues, even if unrelated to the links below.
Building the ascent engine on the Apollo lunar module
Nice detailed video, describing how Bell Aerosystems built an engine that could not fail. It is especially revealing how much testing with real hardware they did prior to launch.
Cool image time! The picture to the right, reduced to post here, was taken by the Webb Space Telescope and released this week by the European Space Agency (ESA). It shows in the near-infrared what the scientists have labeled “The Red Spider Nebula”, a planetary nebula of eruptive gases formed near the end of a star’s life.
Webb’s new view of the Red Spider Nebula reveals for the first time the full extent of the nebula’s outstretched lobes, which form the ‘legs’ of the spider. These lobes, shown in blue, are traced by light emitted from H2 molecules, which contain two hydrogen atoms bonded together. Stretching over the entirety of NIRCam’s field of view, these lobes are shown to be closed, bubble-like structures that each extend about 3 light-years. Outflowing gas from the centre of the nebula has inflated these massive bubbles over thousands of years.
Gas is also actively jetting out from the nebula’s centre, as these new Webb observations show. An elongated purple ‘S’ shape centred on the heart of the nebula follows the light from ionised iron atoms. This feature marks where a fast-moving jet has emerged from near the nebula’s central star and collided with material that was previously cast away by the star, sculpting the rippling structure of the nebula seen today.
It is theorized that a not yet detected second star circles the primary, with both acting as the blades in a blender to mix the gases and help produce these shapes.
Be sure to click on the image to see the full resolution version. It shows the details in the central region much more clearly.
This new NASA/ESA/CSA James Webb Space Telescope Picture of the Month features a cosmic creepy-crawly called NGC 6537 — the Red Spider Nebula. Using its Near-InfraRed Camera (NIRCam), Webb has revealed never-before-seen details in this picturesque planetary nebula with a rich backdrop of thousands of stars. Planetary nebulae like the Red Spider Nebula form when ordinary stars like the Sun reach the end of their lives. After ballooning into cool red giants, these stars shed their outer layers and cast them into space, exposing their white-hot cores. Ultraviolet light from the central star ionises the cast-off material, causing it to glow. The planetary nebula phase of a star’s life is as fleeting as it is beautiful, lasting only a few tens of thousands of years. The central star of the Red Spider Nebula is visible in this image, glowing just brighter than the webs of dusty gas that surround it. The surprising nature of the nebula’s tremendously hot and luminous central star has been revealed by Webb’s NIRCam. In optical-wavelength images, such as from the NASA/ESA Hubble Space Telescope, the star appears faint and blue. But in the NIRCam images, it shows up as red: thanks to its sensitive near-infrared capabilities, Webb has revealed a shroud of hot dust surrounding the central star. This hot dust likely orbits the central star, in a disc structure. Though only a single star is visible in the Red Spider’s heart, a hidden companion star may lurk there as well. A stellar companion could explain the nebula’s shape, including its characteristic narrow waist and wide outflows. This hourglass shape is seen in other planetary nebulae such as the Butterfly Nebula, which Webb also recently observed. Webb’s new view of the Red Spider Nebula reveals for the first time the full extent of the nebula’s outstretched lobes, which form the ‘legs’ of the spider. These lobes, shown in blue, are traced by light emitted from H2 molecules, which contain two hydrogen atoms bonded together. Stretching over the entirety of NIRCam’s field of view, these lobes are shown to be closed, bubble-like structures that each extend about 3 light-years. Outflowing gas from the centre of the nebula has inflated these massive bubbles over thousands of years. Gas is also actively jetting out from the nebula’s centre, as these new Webb observations show. An elongated purple ‘S’ shape centred on the heart of the nebula follows the light from ionised iron atoms. This feature marks where a fast-moving jet has emerged from near the nebula’s central star and collided with material that was previously cast away by the star, sculpting the rippling structure of the nebula seen today. The observations used to create this image come from Webb GO programme #4571 (PI: J. Kastner) as part of a joint Chandra-JWST observing programme, which aims to understand how bipolar planetary nebulae like the Red Spider Nebula are shaped by the outflows and jets that emerge from the stars at their cores. [Image Description: A large planetary nebula. The nebula’s central star is hidden by a blotchy pinkish cloud of dust. A strong red light radiates from this area, illuminating the nearby dust. Two large loops extend diagonally away from the centre, formed of thin ridges of molecular gas, here coloured blue. They stretch out to the corners of the view. A huge number of bright, whitish stars cover the background, also easily visible through the thin dust layers.] Links Science paper Annotated image Slider tool: Hubble and Webb’s views of NGC 6537 Image on ESA website Pan video Transition Video: Hubble and Webb’s views of NGC 6537 Space Sparks Episode
The glittering galaxy in this NASA/ESA Hubble Space Telescope Picture of the Week is NGC 6951, which resides about 70 million light-years away in the constellation Cepheus. As this Hubble image shows, NGC 6951 is a spiral galaxy with plenty of intriguing structures. Most eye-catching are its spiral arms, which are dotted with brilliant red nebulae, bright blue stars and filamentary dust clouds. The spiral arms loop around the galactic centre, which has a golden glow that comes from a population of older stars. The centre of the galaxy is also distinctly elongated, revealing the presence of a slowly rotating bar of stars. NGC 6951’s bar may be responsible for another remarkable feature: a white-blue ring that encloses the very heart of the galaxy. This is called a circumnuclear starburst ring — essentially, a circle of enhanced star formation around the nucleus of a galaxy. The bar funnels gas toward the centre of the galaxy, where it collects in a ring about 3800 light-years across. Two dark dust lanes that run parallel to the bar mark the points where gas from the bar enters the ring. The dense gas of a circumnuclear starburst ring is the perfect environment to churn out an impressive number of stars. Using data from Hubble, astronomers have identified more than 80 potential star clusters within NGC 6951’s ring. Many of the stars formed less than 100 million years ago, but the ring itself is longer-lived, potentially having existed for 1–1.5 billion years. Astronomers have imaged NGC 6951 with Hubble for a wide variety of reasons, including mapping the dust in nearby galaxies, studying the centres of disc galaxies and keeping tabs on recent supernovae (of which NGC 6951 has hosted five or six). [Image Description: A spiral galaxy with large, open arms. A bar of yellow light, where old stars are gathered, crosses the middle of the disk. The very centre is a white point surrounded by a small, shining ring of star clusters. Thin lanes of dust swirl around this ring, reaching out to follow the spiral arms; also visible across the arms are red, glowing spots where stars are forming. To the right a star shines large and bright.]
