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Webb depicts staggering structure in 19 nearby spiral galaxies

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19 Nineteen Webb images of face-on spiral galaxies are combined in a mosaic, some within squares, and others horizontal or vertical rectangles. Galaxies’ spiral arms appear in shades of orange, and many of their centres have light blue hazes.

Webb depicts staggering structure in 19 nearby spiral galaxies

A new treasure trove of images from the NASA/ESA/CSA James Webb Space Telescope showcases near- and mid-infrared portraits of 19 face-on spiral galaxies. This new set of exquisite images show stars, gas, and dust on the smallest scales ever observed beyond our own galaxy. Teams of researchers are studying these images to uncover the origins of these intricate structures. The research community’s collective analysis will ultimately inform theorists’ simulations, and advance our understanding of star formation and the evolution of spiral galaxies.

19 Nineteen Webb images of face-on spiral galaxies are combined in a mosaic, some within squares, and others horizontal or vertical rectangles. Galaxies’ spiral arms appear in shades of orange, and many of their centres have light blue hazes.
This collection of 19 face-on spiral galaxies from the NASA/ESA/CSA James Webb Space Telescope in near- and mid-infrared light is at once overwhelming and awe-inspiring. Webb’s NIRCam (Near-Infrared Camera) captured millions of stars in these images. Older stars appear blue here, and are clustered at the galaxies’ cores. The telescope’s MIRI (Mid-Infrared Instrument) observations highlight glowing dust, showing where it exists around and between stars – appearing in shades of red and orange. Stars that haven’t yet fully formed and are encased in gas and dust appear bright red.
Webb’s high-resolution images are the first to show large, spherical shells in the gas and dust in such exquisite detail. These holes may have been created by stars that exploded and carved out giant regions in the interstellar material.
Another eye-catching detail? Several galaxy cores are awash in pink-and-red diffraction spikes. These are clear signs that these galaxies may have central active supermassive black holes or central star clusters.
These spiral galaxies are Webb’s first big batch of contributions to the Physics at High Angular resolution in Nearby GalaxieS (PHANGS) program, that includes existing images and data from the NASA/ESA Hubble Space Telescope, the Very Large Telescope’s Multi-Unit Spectroscopic Explorer (MUSE), and the Atacama Large Millimetre/submillimetre Array (ALMA). With Webb’s images, researchers can now examine these galaxies in ultraviolet, visible, infrared, and radio light.
Credit: NASA, ESA, CSA, STScI, J. Lee (STScI), T. Williams (Oxford), PHANGS Team, E. Wheatley (STScI)

If you follow each of the galaxy’s clearly defined arms, which are brimming with stars, to their centres, there may be old star clusters and – sometimes – active supermassive black holes. Only the James Webb Space Telescope can deliver highly detailed scenes of nearby galaxies in a combination of near- and mid-infrared light – and a set of these images were publicly released today.

These Webb images are part of a large, long-standing project, the Physics at High Angular resolution in Nearby GalaxieS (PHANGS) programme, which is supported by more than 150 astronomers worldwide. Before Webb took these images, PHANGS was already brimming with data from the NASA/ESA Hubble Space Telescope, the Very Large Telescope’s Multi-Unit Spectroscopic Explorer, and the Atacama Large Millimetre/submillimetre Array, including observations in ultraviolet, visible, and radio light. Webb’s near- and mid-infrared contributions have provided several new puzzle pieces.

Webb’s NIRCam (Near-Infrared Camera) captured millions of stars in these images, which sparkle in blue tones. Some stars are spread throughout the spiral arms, but others are clumped tightly together in star clusters.

The telescope’s MIRI (Mid-Infrared Instrument) data highlights glowing dust, showing us where it exists behind, around, and between stars. It also spotlights stars that haven’t yet fully formed – they are still encased in the gas and dust that feed their growth, like bright red seeds at the tips of dusty peaks.

To the amazement of astronomers, Webb’s images also show large, spherical shells in the gas and dust that may have been created by exploded stars.

The spiral arms’ extended regions of gas also reveal details in red and orange. Astronomers study the spacing of these features to learn how a galaxy distributes its gas and dust. These structures will provide key insights about how galaxies build, maintain, and shut off star formation.

Evidence shows that galaxies grow from inside out – star formation begins at galaxies’ cores and spreads along their arms, spiralling away from the centre. The farther a star is from the galaxy’s core, the more likely it is to be younger. In contrast, the areas near the cores that look lit by a blue spotlight are populations of older stars. The galaxy cores that are awash in pink-and-red diffraction spikes may indicate an active supermassive black hole or saturation from bright star clusters toward the centre.

There are many avenues of research that scientists can begin to pursue with the combined PHANGS data, but the unprecedented number of stars Webb resolved are a great place to begin. In addition to immediately releasing these images, the PHANGS team has also released the largest catalogue to date of roughly 100 000 star clusters.

 

Press release from ESA Webb.

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Webb discovers dusty cat’s tail in Beta Pictoris System

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A wide, thin horizontal orange line appears at the centre, extending almost to the edges, a debris disc seen edge-on. A thin blue-green disc is inclined about five degrees counterclockwise relative to the main orange disc. Cloudy, translucent grey material is most prominent near the orange main debris disc. Some of the grey material forms a curved feature in the upper right, resembling a cat’s tail. At the centre is a black circle with a bar. The central star, represented as a small white star icon, is blocked by an instrument known as a coronagraph. The background of space is black.

Webb discovers dusty cat’s tail in Beta Pictoris System

Beta Pictoris, a young planetary system located just 63 light-years away, continues to intrigue scientists even after decades of in-depth study. It possesses the first dust disc imaged around another star — a disc of debris produced by collisions between asteroids, comets, and planetesimals. Observations from the NASA/ESA Hubble Space Telescope revealed a second debris disc in this system [1], inclined with respect to the first. Now, a team of astronomers using the NASA/ESA/CSA James Webb Space Telescope to image the Beta Pictoris (Beta Pic) system has discovered a new, previously unseen structure.

A wide, thin horizontal orange line appears at the centre, extending almost to the edges, a debris disc seen edge-on. A thin blue-green disc is inclined about five degrees counterclockwise relative to the main orange disc. Cloudy, translucent grey material is most prominent near the orange main debris disc. Some of the grey material forms a curved feature in the upper right, resembling a cat’s tail. At the centre is a black circle with a bar. The central star, represented as a small white star icon, is blocked by an instrument known as a coronagraph. The background of space is black.
This image from Webb’s MIRI (Mid-Infrared Instrument) shows the star system Beta Pictoris. An edge-on disc of dusty debris generated by collisions between planetesimals (orange) dominates the view. A hotter, secondary disc (cyan) is inclined by about 5 degrees relative to the primary disc. The curved feature at upper right, which the science team nicknamed the “cat’s tail,” has never been seen before. A coronagraph (black circle and bar) has been used to block the light of the central star, whose location is marked with a white star shape. In this image light at 15.5 microns is coloured cyan and 23 microns is orange (filters F1550C and F2300C, respectively).
Credit: NASA, ESA, CSA, STScI, C. Stark and K. Lawson (NASA GSFC), J. Kammerer (ESO), and M. Perrin (STScI)

The team, led by Isabel Rebollido of the Astrobiology Center in Spain, and now an ESA Research Fellow, used Webb’s NIRCam (Near-Infrared Camera) and MIRI (Mid-Infrared Instrument) to investigate the composition of Beta Pic’s previously detected main and secondary debris discs. The results exceeded their expectations, revealing a sharply inclined branch of dust, shaped like a cat’s tail, that extends from the southwest portion of the secondary debris disc.

“Beta Pictoris is the debris disc that has it all: It has a really bright, close star that we can study very well,” said Rebollido. “While there have been previous observations from the ground in this wavelength range, they did not have the sensitivity and the spatial resolution that we now have with Webb, so they didn’t detect this feature.”

A wide, thin horizontal orange line appears at the centre, extending almost to the edges, a debris disc seen edge-on. A thin blue-green disc is inclined about five degrees counterclockwise relative to the main orange disc. Cloudy, translucent grey material is most prominent near the orange main debris disc. Some of the grey material forms a curved feature in the upper right, resembling a cat’s tail. At the centre is a black circle with a bar. The central star, represented as a small white star icon, is blocked by an instrument known as a coronagraph. The background of space is black.
This image from Webb’s MIRI (Mid-Infrared Instrument) shows the star system Beta Pictoris. An edge-on disc of dusty debris generated by collisions between planetesimals (orange) dominates the view. A hotter, secondary disc (cyan) is inclined by about 5 degrees relative to the primary disc. The curved feature at upper right, which the science team nicknamed the “cat’s tail,” has never been seen before. A coronagraph (black circle and bar) has been used to block the light of the central star, whose location is marked with a white star shape. In this image light at 15.5 microns is coloured cyan and 23 microns is orange (filters F1550C and F2300C, respectively).
Credit:
NASA, ESA, CSA, STScI, C. Stark and K. Lawson (NASA GSFC), J. Kammerer (ESO), and M. Perrin (STScI)

A Star’s Portrait Improved with Webb

Even with Webb, peering at Beta Pic in the right wavelength range — in this case, the mid-infrared — was crucial to detect the cat’s tail, as it only appeared in the MIRI data. Webb’s mid-infrared data also revealed differences in temperature between Beta Pic’s two discs, which likely is due to differences in composition.

“We didn’t expect Webb to reveal that there are two different types of material around Beta Pic, but MIRI clearly showed us that the material of the secondary disc and cat’s tail is hotter than the main disc,” said Christopher Stark, a co-author of the study at NASA’s Goddard Space Flight Center in Greenbelt, Maryland. “The dust that forms that disc and tail must be very dark, so we don’t easily see it at visible or near-infrared wavelengths — but in the mid-infrared, it’s glowing.”

To explain the hotter temperature, the team deduced that the dust may be highly porous “organic refractory material,” similar to the matter found on the surfaces of comets and asteroids in our solar system. For example, a preliminary analysis of material sampled from asteroid Bennu by NASA’s OSIRIS-Rex mission found it to be very dark and carbon-rich, much like what MIRI detected at Beta Pic.

The Tail’s Puzzling Beginning Warrants Future Research

However, a major lingering question remains: What could explain the shape of the cat’s tail, a uniquely curved feature unlike what is seen in discs around other stars?

Rebollido and the team modelled various scenarios in an attempt to emulate the cat’s tail and unravel its origins. Though further research and testing is required, the team presents a strong hypothesis that the cat’s tail is the result of a dust production event that occurred a mere one hundred years ago.

“Something happens — like a collision — and a lot of dust is produced,” shared Marshall Perrin, a co-author of the study at the Space Telescope Science Institute in Baltimore, Maryland. “At first, the dust goes in the same orbital direction as its source, but then it also starts to spread out. The light from the star pushes the smallest, fluffiest dust particles away from the star faster, while the bigger grains do not move as much, creating a long tendril of dust.”

“The cat’s tail feature is highly unusual, and reproducing the curvature with a dynamical model was difficult,” explained Stark. “Our model requires dust that can be pushed out of the system extremely rapidly, which again suggests it’s made of organic refractory material.”

The team’s preferred model explains the sharp angle of the tail away from the disc as a simple optical illusion. Our perspective combined with the curved shape of the tail creates the observed angle of the tail, while in fact, the arc of material is only departing from the disc at a five-degree incline. Taking into consideration the tail’s brightness, the team estimates the amount of dust within the cat’s tail to be equivalent to a large main belt asteroid spread out across 16 billion kilometres.

A recent dust production event within Beta Pic’s debris discs could also explain an asymmetry previously spotted by the Atacama Large Millimeter/submillimeter Array in 2014: a clump of carbon monoxide (CO) located near the cat’s tail. Since the star’s radiation should break down CO within roughly one hundred years, this still-present concentration of gas could be lingering evidence of the same event.

“Our research suggests that Beta Pic may be even more active and chaotic than we had previously thought,” said Stark. “Webb continues to surprise us, even when looking at the most well-studied objects. We have a completely new window into these planetary systems.”

These results were presented in a press conference at the 243rd meeting of the American Astronomical Society in New Orleans, Louisiana.

The observations were taken as part of Guaranteed Time Observation program 1411.

Notes

[1] Learn more about these 2006 Hubble observations that revealed a second debris disc in the Beta Pic system here.

A wide, thin horizontal orange line appears at the centre, extending almost to the edges, a debris disc seen edge-on. A thin blue-green disc is inclined about five degrees counterclockwise relative to the main orange disc. Cloudy, translucent grey material is most prominent near the orange main debris disc. Some of the grey material forms a curved feature in the upper right, resembling a cat’s tail. At the centre is a black circle with a bar. The central star, represented as a small white star icon, is blocked by an instrument known as a coronagraph. The background of space is black.
This image from Webb’s MIRI (Mid-Infrared Instrument) shows the star system Beta Pictoris. An edge-on disc of dusty debris generated by collisions between planetesimals (orange) dominates the view. A hotter, secondary disc (cyan) is inclined by about 5 degrees relative to the primary disc. The curved feature at upper right, which the science team nicknamed the “cat’s tail,” has never been seen before. A coronagraph (black circle and bar) has been used to block the light of the central star, whose location is marked with a white star shape. In this image light at 15.5 microns is coloured cyan and 23 microns is orange (filters F1550C and F2300C, respectively).
Credit: NASA, ESA, CSA, STScI, C. Stark and K. Lawson (NASA GSFC), J. Kammerer (ESO), and M. Perrin (STScI)

 

Press release from ESA Webb.

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Webb looks for Fomalhaut’s asteroid belt and finds much more

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Webb asteroid belt Fomalhaut’s The NASA/ESA Hubble Space Telescope and ESA's Herschel Space Observatory, as well as the Atacama Large Millimeter/submillimeter Array (ALMA), have previously taken sharp images of the outermost belt. However, none of them found any structure interior to it. [Image description: An orange oval extends from the 1 o’clock to 7 o’clock positions. It features a prominent outer ring, a darker gap, an intermediate ring, a narrower dark gap, and a bright inner disc. At the centre is a ragged black spot indicating a lack of data.] Credit: NASA, ESA, CSA, A. Pagan (STScI), A. Gáspár (University of Arizona)

Webb looks for Fomalhaut’s asteroid belt and finds much more

Astronomers used the NASA/ESA/CSA James Webb Space Telescope to image the warm dust around a nearby young star, Fomalhaut, in order to study the first asteroid belt ever seen outside of our Solar System in infrared light. But to their surprise, they found that the dusty structures are much more complex than the asteroid and Kuiper dust belts of our Solar System. Overall, there are three nested belts extending out to 23 billion kilometres from the star — that’s 150 times the distance of Earth from the Sun. The scale of the outermost belt is roughly twice the scale of our Solar System’s Kuiper Belt of small bodies and cold dust beyond Neptune. The inner belts — which had never been seen before — were revealed by Webb for the first time.

Webb Fomalhaut’s asteroid beltThe NASA/ESA Hubble Space Telescope and ESA's Herschel Space Observatory, as well as the Atacama Large Millimeter/submillimeter Array (ALMA), have previously taken sharp images of the outermost belt. However, none of them found any structure interior to it. [Image description: An orange oval extends from the 1 o’clock to 7 o’clock positions. It features a prominent outer ring, a darker gap, an intermediate ring, a narrower dark gap, and a bright inner disc. At the centre is a ragged black spot indicating a lack of data.] Credit: NASA, ESA, CSA, A. Pagan (STScI), A. Gáspár (University of Arizona)
Webb looks for Fomalhaut’s asteroid belt and finds much more. This image of the dusty debris disc surrounding the young star Fomalhaut is from Webb’s Mid-Infrared Instrument (MIRI). It reveals three nested belts extending out to 23 billion kilometres from the star. The inner belts — which had never been seen before — were revealed by Webb for the first time.
The NASA/ESA Hubble Space Telescope and ESA’s Herschel Space Observatory, as well as the Atacama Large Millimeter/submillimeter Array (ALMA), have previously taken sharp images of the outermost belt. However, none of them found any structure interior to it.
These belts are most likely shaped by the gravitational forces produced by unseen planets. Credit: NASA, ESA, CSA, A. Pagan (STScI), A. Gáspár (University of Arizona)
The belts encircle the young hot star, which can be seen with the naked eye as the brightest star in the southern constellation Piscis Austrinus. The dusty belts are the debris from collisions of larger bodies, analogous to asteroids and comets, and are frequently described as ‘debris discs’. 

“I would describe Fomalhaut as the archetype of debris discs found elsewhere in our galaxy, because it has components similar to those we have in our own planetary system,” said András Gáspár of the University of Arizona in Tucson and lead author of a new paper describing these results. “By looking at the patterns in these rings, we can actually start to make a little sketch of what a planetary system ought to look like — if we could actually take a deep enough picture to see the suspected planets.”

The NASA/ESA Hubble Space Telescope and ESA’s Herschel Space Observatory, as well as the Atacama Large Millimeter/submillimeter Array (ALMA), have previously taken sharp images of the outermost belt. However, none of them found any structure interior to it. The inner belts have been resolved for the first time by Webb in infrared light.

“Where Webb really excels is that we’re able to physically resolve the thermal glow from dust in those inner regions. So you can see inner belts that we could never see before,” said Schuyler Wolff, another member of the team at the University of Arizona.

Hubble, ALMA, and Webb are tag-teaming to assemble a holistic view of the debris discs around a number of stars. “With Hubble and ALMA, we were able to image a bunch of Kuiper Belt analogues, and we’ve learned loads about how outer discs form and evolve,” said Wolff. “But we need Webb to allow us to image a dozen or so asteroid belts elsewhere. We can learn just as much about the inner warm regions of these discs as Hubble and ALMA taught us about the colder outer regions.”

These belts are most likely shaped by the gravitational forces produced by unseen planets. Similarly, inside our Solar System Jupiter corrals the asteroid belt, the inner edge of the Kuiper Belt is sculpted by Neptune, and the outer edge could be shepherded by as-yet-unseen bodies beyond it. As Webb images more systems, we will learn about the configurations of their planets.

Webb looks for Fomalhaut’s asteroid belt and finds much more. This image of the Fomalhaut system, captured by Webb’s Mid-Infrared Instrument (MIRI), shows compass arrows, scale bar, and colour key for reference. Labels indicate the various structures. At right, a great dust cloud is highlighted and pullouts show it in two infrared wavelengths: 23 and 25.5 microns.
The north and east compass arrows show the orientation of the image on the sky. Note that the relationship between north and east on the sky (as seen from below) is flipped relative to direction arrows on a map of the ground (as seen from above).
The scale bar is labelled in astronomical units, which is the average distance between Earth and the Sun: 150 million kilometres. The outer ring is about 240 astronomical units in diameter.
This image shows invisible mid-infrared wavelengths of light that have been translated into visible-light colours. The colour key and labels show which MIRI filters were used when collecting the light.
Credit: NASA, ESA, CSA, A. Pagan (STScI), A. Gáspár (University of Arizona)

Fomalhaut’s dust ring was discovered in 1983 in observations made by NASA’s Infrared Astronomical Satellite (IRAS). The existence of the ring has also been inferred from previous and longer-wavelength observations using submillimetre telescopes on Maunakea, Hawai‘i, NASA’s Spitzer Space Telescope, and Caltech’s Submillimeter Observatory.

“The belts around Fomalhaut are kind of a mystery novel: Where are the planets?” said George Rieke, another team member and US science lead for Webb’s Mid-Infrared Instrument (MIRI), which made these observations. “I think it’s not a very big leap to say there’s probably a really interesting planetary system around the star.”

“We definitely didn’t expect the more complex structure with the second intermediate belt and then the broader asteroid belt,” added Wolff. “That structure is very exciting because any time an astronomer sees a gap and rings in a disc, they say, ‘There could be an embedded planet shaping the rings!’”

Webb also imaged what Gáspár dubs ‘the great dust cloud’, which may be evidence for a collision occurring in the outer ring between two protoplanetary bodies. This is a different feature from the suspected planet first seen inside the outer ring by Hubble in 2008. Subsequent Hubble observations showed that by 2014 the object had vanished. A plausible interpretation is that this newly discovered feature, like the earlier one, is an expanding cloud of very fine dust particles from two icy bodies that smashed into each other.

The idea of a protoplanetary disc around a star goes back to the late 1700s when astronomers Immanuel Kant and Pierre-Simon Laplace independently developed the theory that the Sun and planets formed from a rotating gas cloud that collapsed and flattened under gravity. Debris discs develop later, following the formation of planets and dispersal of the primordial gas in the systems. They show that small bodies like asteroids are colliding catastrophically and pulverising their surfaces into huge clouds of dust and other debris. Observations of dust provide unique clues to the structure of an exoplanetary system, reaching down to Earth-sized planets and even asteroids, which are much too small to see individually.

“This very exciting result highlights the unique power of MIRI to study the structures carved by planets in the innermost regions of circumstellar discs,“ adds Gillian Wright, European principal investigator for MIRI and Director of the UK Astronomy Technology Centre (UKATC).

The team’s results are being published in the journal Nature Astronomy.

 

Press release from ESA Webb.

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ALMA finds possible sign of neutron star in supernova 1987A

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Supernova 1987A

ALMA finds possible sign of neutron star in supernova 1987A

Two teams of astronomers have made a compelling case in the 33-year-old mystery surrounding Supernova 1987A. Based on observations of the Atacama Large Millimeter/submillimeter Array (ALMA) and a theoretical follow-up study, the scientists provide new insight for the argument that a neutron star is hiding deep inside the remains of the exploded star. This would be the youngest neutron star known to date.

 

Supernova 1987A
This artist’s illustration of Supernova 1987A shows the dusty inner regions of the exploded star’s remnants (red), in which a neutron star might be hiding. This inner region is contrasted with the outer shell (blue), where the energy from the supernova is colliding (green) with the envelope of gas ejected from the star prior to its powerful detonation. Credits: NRAO/AUI/NSF, B. Saxton

Ever since astronomers witnessed one of the brightest explosions of a star in the night sky, creating Supernova 1987A (SN 1987A), they have been searching for a compact object that should have formed in the leftovers from the blast.

Because particles known as neutrinos were detected on Earth on the day of the explosion (23 February 1987), astronomers expected that a neutron star had formed in the collapsed center of the star. But when scientists could not find any evidence for that star, they started to wonder whether it subsequently collapsed into a black hole instead. For decades the scientific community has been eagerly awaiting a signal from this object that has been hiding behind a very thick cloud of dust.

The “blob”

Supernova 1987A
Extremely high-resolution ALMA images revealed a hot “blob” in the dusty core of Supernova 1987A (inset), which could be the location of the missing neutron star. The red color shows dust and cold gas in the center of the supernova remnant, taken at radio wavelengths with ALMA. The green and blue hues reveal where the expanding shock wave from the exploded star is colliding with a ring of material around the supernova. The green represents the glow of visible light, captured by NASA’s Hubble Space Telescope. The blue color reveals the hottest gas and is based on data from NASA’s Chandra X-ray Observatory. The ring was initially made to glow by the flash of light from the original explosion. Over subsequent years the ring material has brightened considerably as the explosion’s shock wave slams into it. Credits: ALMA (ESO/NAOJ/NRAO), P. Cigan and R. Indebetouw; NRAO/AUI/NSF, B. Saxton; NASA/ESA

Recently, observations from the ALMA radio telescope provided the first indication of the missing neutron star after the explosion. Extremely high-resolution images revealed a hot “blob” in the dusty core of SN 1987A, which is brighter than its surroundings and matches the suspected location of the neutron star.

“We were very surprised to see this warm blob made by a thick cloud of dust in the supernova remnant,” said Mikako Matsuura from Cardiff University and a member of the team that found the blob with ALMA. “There has to be something in the cloud that has heated up the dust and which makes it shine. That’s why we suggested that there is a neutron star hiding inside the dust cloud.”

Even though Matsuura and her team were excited about this result, they wondered about the brightness of the blob. “We thought that the neutron star might be too bright to exist, but then Dany Page and his team published a study that indicated that the neutron star can indeed be this bright because it is so very young,” said Matsuura.

Dany Page is an astrophysicist at the National Autonomous University of Mexico, who has been studying SN 1987A from the start. “I was halfway through my PhD when the supernova happened,” he said, “it was one of the biggest events in my life that made me change the course of my career to try to solve this mystery. It was like a modern holy grail.”

The theoretical study by Page and his team, published today in The Astrophysical Journal, strongly supports the suggestion made by the ALMA team that a neutron star is powering the dust blob. “In spite of the supreme complexity of a supernova explosion and the extreme conditions reigning in the interior of a neutron star, the detection of a warm blob of dust is a confirmation of several predictions,” Page explained.

These predictions were the location and the temperature of the neutron star. According to supernova computer models, the explosion has “kicked away” the neutron star from its birthplace with a speed of hundreds of kilometers per second (tens of times faster than the fastest rocket). The blob is exactly at the place where astronomers think the neutron star would be today. And the temperature of the neutron star, which was predicted to be around 5 million degrees Celsius, provides enough energy to explain the brightness of the blob.

Not a pulsar or a black hole

Contrary to common expectations, the neutron star is likely not a pulsar. “A pulsar’s power depends on how fast it spins and on its magnetic field strength, both of which would need to have very finely tuned values to match the observations,” said Page, “while the thermal energy emitted by the hot surface of the young neutron star naturally fits the data.”

“The neutron star behaves exactly like we expected,” added James Lattimer of Stony Brook University in New York, and a member of Page’s research team. Lattimer has also followed SN 1987A closely, having published prior to SN 1987A predictions of a supernova’s neutrino signal that subsequently matched the observations. “Those neutrinos suggested that a black hole never formed, and moreover it seems difficult for a black hole to explain the observed brightness of the blob. We compared all possibilities and concluded that a hot neutron star is the most likely explanation.”

This neutron star is a 25 km wide, extremely hot ball of ultra-dense matter. A teaspoon of its material would weigh more than all the buildings within New York City combined. Because it can only be 33 years old, it would be the youngest neutron star ever found. The second youngest neutron star that we know of is located in the supernova remnant Cassiopeia A and is 330 years old.

Only a direct picture of the neutron star would give definite proof that it exists, but for that astronomers may need to wait a few more decades until the dust and gas in the supernova remnant become more transparent.

Detailed ALMA images

This colorful, multiwavelength image of the intricate remains of Supernova 1987A is produced with data from three different observatories. The red color shows dust and cold gas in the center of the supernova remnant, taken at radio wavelengths with ALMA. The green and blue hues reveal where the expanding shock wave from the exploded star is colliding with a ring of material around the supernova. The green represents the glow of visible light, captured by NASA’s Hubble Space Telescope. The blue color reveals the hottest gas and is based on data from NASA’s Chandra X-ray Observatory. The ring was initially made to glow by the flash of light from the original explosion. Over subsequent years the ring material has brightened considerably as the explosion’s shock wave slams into it. Credits: ALMA (ESO/NAOJ/NRAO), P. Cigan and R. Indebetouw; NRAO/AUI/NSF, B. Saxton; NASA/ESA

Even though many telescopes have made images of SN 1987A, none of them have been able to observe its core with such high precision as ALMA. Earlier (3-D) observations with ALMA already showed the types of molecules found in the supernova remnant and confirmed that it produced massive amounts of dust.

“This discovery builds upon years of ALMA observations, showing the core of the supernova in more and more detail thanks to the continuing improvements to the telescope and data processing,” said Remy Indebetouw of the National Radio Astronomy Observatory and the University of Virginia, who has been a part of the ALMA imaging team.

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This research is presented in two papers:

ALMA observation of the “blob”: “High Angular Resolution ALMA Images of Dust and Molecules in the SN 1987A Ejecta”, by P. Cigan et al., The Astrophysical Journal. https://doi.org/10.3847/1538-4357/ab4b46

Theoretical study favoring a neutron star: “NS 1987A in SN 1987A”, by D. Page et al., The Astrophysical Journal. https://doi.org/10.3847/1538-4357/ab93c2

The National Radio Astronomy Observatory is a facility of the National Science Foundation, operated under cooperative agreement by Associated Universities, Inc.

The Atacama Large Millimeter/submillimeter Array (ALMA), an international astronomy facility, is a partnership of the European Organisation for Astronomical Research in the Southern Hemisphere (ESO), the U.S. National Science Foundation (NSF) and the National Institutes of Natural Sciences (NINS) of Japan in cooperation with the Republic of Chile. ALMA is funded by ESO on behalf of its Member States, by NSF in cooperation with the National Research Council of Canada (NRC) and the Ministry of Science and Technology (MOST) and by NINS in cooperation with the Academia Sinica (AS) in Taiwan and the Korea Astronomy and Space Science Institute (KASI).

ALMA construction and operations are led by ESO on behalf of its Member States; by the National Radio Astronomy Observatory (NRAO), managed by Associated Universities, Inc. (AUI), on behalf of North America; and by the National Astronomical Observatory of Japan (NAOJ) on behalf of East Asia. The Joint ALMA Observatory (JAO) provides the unified leadership and management of the construction, commissioning and operation of ALMA.

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Press release on Supernova 1987A from the National Radio Astronomy Observatory

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ALMA spots twinkling heart of Milky Way

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ALMA Milky Way

Astronomers using the Atacama Large Millimeter/submillimeter Array (ALMA) found quasi-periodic flickers in millimeter-waves from the center of the Milky Way, Sagittarius (Sgr) A*. The team interpreted these blinks to be due to the rotation of radio spots circling the supermassive black hole with an orbit radius smaller than that of Mercury. This is an interesting clue to investigate space-time with extreme gravity.

“It has been known that Sgr A* sometimes flares up in millimeter wavelength,” tells Yuhei Iwata, the lead author of the paper published in the Astrophysical Journal Letters and a graduate student at Keio University, Japan. “This time, using ALMA, we obtained high-quality data of radio-wave intensity variation of Sgr A* for 10 days, 70 minutes per day. Then we found two trends: quasi-periodic variations with a typical time scale of 30 minutes and hour-long slow variations.”

The different color dots show the flux at different frequencies (blue: 234.0 GHz, green: 219.5 GHz, red: 217.5 GHz). Variations with about a 30-minute period are seen in the diagram. Credits: Y. Iwata et al./Keio University

Astronomers presume that a supermassive black hole with a mass of 4 million suns is located at the center of Sgr A*. Flares of Sgr A* have been observed not only in millimeter wavelength, but also in infrared light and X-ray. However, the variations detected with ALMA are much smaller than the ones previously detected, and it is possible that these levels of small variations always occur in Sgr A*.

ALMA Milky Way
Hot spots circling around the black hole could produce the quasi-periodic millimeter emission detected with ALMA. Credits: Keio University

The black hole itself does not produce any kind of emission. The source of the emission is the scorching gaseous disk around the black hole. The gas around the black hole does not go straight to the gravitational well, but it rotates around the black hole to form an accretion disk.

The team focused on short timescale variations and found that the variation period of 30 minutes is comparable to the orbital period of the innermost edge of the accretion disk with the radius of 0.2 astronomical units (1 astronomical unit corresponds to the distance between the Earth and the Sun: 150 million kilometers). For comparison, Mercury, the solar system’s innermost planet, circles around the Sun at a distance of 0.4 astronomical units. Considering the colossal mass at the center of the black hole, its gravity effect is also extreme in the accretion disk.

“This emission could be related with some exotic phenomena occurring at the very vicinity of the supermassive black hole,” says Tomoharu Oka, a professor at Keio University.

Their scenario is as follows. Hot spots are sporadically formed in the disk and circle around the black hole, emitting strong millimeter waves. According to Einstein’s special relativity theory, the emission is largely amplified when the source is moving toward the observer with a speed comparable to that of light. The rotation speed of the inner edge of the accretion disk is quite large, so this extraordinary effect arises. The astronomers believe that this is the origin of the short-term variation of the millimeter emission from Sgr A*.

The team supposes that the variation might affect the effort to make an image of the supermassive black hole with the Event Horizon Telescope. “In general, the faster the movement is, the more difficult it is to take a photo of the object,” says Oka. “Instead, the variation of the emission itself provides compelling insight for the gas motion. We may witness the very moment of gas absorption by the black hole with a long-term monitoring campaign with ALMA.” The researchers aim to draw out independent information to understand the mystifying environment around the supermassive black hole.

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The research team members are: Yuhei Iwata (Keio University), Tomoharu Oka (Keio University), Masato Tsuboi (Japan Space Exploration Agency/The University of Tokyo), Makoto Miyoshi (National Astronomical Observatory of Japan/SOKENDAI), and Shunya Takekawa (National Astronomical Observatory of Japan)

Press release on ALMA spotting twinkling heart of Milky Way from the National Institutes of Natural Sciences

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