ST/ Elusive, dusty inner region of distant galaxy

Paradigm

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Paradigm

36 min readNov 23, 2022

Space biweekly vol.65, 9th November — 23d November

TL;DR

An international team of scientists has achieved the milestone of directly observing the long-sought, innermost dusty ring around a supermassive black hole, at a right angle to its emerging jet. Such a structure was thought to exist in the nucleus of galaxies but had been difficult to observe directly because intervening material obscured our line of sight.
A research team has reconstructed the origin of an unusual gravitational wave signal. The signal GW190521 may result from the merger of two massive black holes that captured each other in their gravitational field and then collided while spinning around each other in a rapid, eccentric motion.
New data throws out the textbook picture of a spherical stellar halo and reinforces a dynamic origin story of two galaxies that collided billions of years ago.
When Mars was a young planet, it was bombarded by icy asteroids that delivered water and organic chemistry necessary for life to emerge. According to the professor behind a new study, this means that the first life in our solar system may have been on Mars.
A team of astronomers has found that planet formation in our young Solar System started much earlier than previously thought, with the building blocks of planets growing at the same time as their parent star.
First in line to receive data transmissions from the James Webb Space Telescope, a team of astronomers is using unprecedentedly clear observations to reveal the secret inner workings of galaxies.
An international research team has succeeded in significantly narrowing the scope for the existence of dark matter. The experiment makes an important contribution to the search for these particles.
Space scientists may need to rethink how gamma-ray bursts are formed after new research shows new-born supermassive stars, not black holes, are sometimes responsible for these huge extragalactic bursts of energy.
It is still a glimpse into the future: Astronauts could be put into artificial hibernation and in this state be better protected from cosmic radiation. At present, there are already promising approaches to follow up such considerations. An international research team now has found decisive indications of the possible benefits of artificial hibernation for radiation resistance.
In two connected studies, engineers, astrophysicists, astrobiologists, and astronauts lay out the research that needs to be done to get us closer to answering the old-age question about life beyond Earth, and explore the possibility of extraterrestrial life living in caves.
Upcoming industry events. And more!

Space industry in numbers

The global smart space market size is projected to grow from USD 9.4 billion in 2020 to USD 15.3 billion by 2025, at a Compound Annual Growth Rate (CAGR) of 10.2% during the forecast period. The increasing venture capital funding and growing investments in smart space technology to drive market growth.

Analysts at Morgan Stanley and Goldman Sachs have predicted that economic activity in space will become a multi-trillion-dollar market in the coming decades. Morgan Stanley’s Space Team estimates that the roughly USD 350 billion global space industry could surge to over USD 1 trillion by 2040.

Source: Satellite Industry Association, Morgan Stanley Research, Thomson Reuters. *2040 estimates

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Latest research

The Dust Sublimation Region of the Type 1 AGN NGC 4151 at a Hundred Microarcsecond Scale as Resolved by the CHARA Array Interferometer

by Makoto Kishimoto, Matthew Anderson, Theo ten Brummelaar, et al in The Astrophysical Journal

An international team of scientists has achieved the milestone of directly observing the long-sought, innermost dusty ring around a supermassive black hole, at a right angle to its emerging jet. Such a structure was thought to exist in the nucleus of galaxies but had been difficult to observe directly because intervening material obscured our line of sight.

Now the inner disk is detected using the highest spatial resolution in the infrared wavelengths ever done for an extragalactic object.

“This is a very exciting step forward to view the inner region of a distant galaxy with such fine detail,” said Gail Schaefer, Associate Director of the Center for High Angular Resolution Astronomy (CHARA) Array.

Sampled uv points, color-coded with observed visibility squared.

A supermassive black hole is thought to exist at the center of every large galaxy. As material in the surrounding region gets pulled toward the center, the gas forms a hot and bright disk-like structure. In some cases, a jet emerges from the vicinity of the black hole in a direction at a right angle to the disk. However, this flat structure, which is essentially the ‘engine’ of this active supermassive black hole system, has never been directly seen because it’s too small to be captured by conventional telescopes.

One way to approach this key structure is to directly see an outer ‘dusty ring’ — interstellar gas contains dust grains, tiny solid particles made of heavy elements, which can only survive in the outer region where temperature is low enough (< ~1500K — otherwise metals evaporate). The heated dust emits thermal infrared radiation, and thus would look like an outer ring around the black hole, if the central system indeed has a flat structure. The detection of its structure would be a key step to delineate how the central engine works.

Attempts to see this structure from edge-on directions are difficult, because the system is obscured by the same dust acting as an absorber of light. Instead, in the new investigation the team focused on a system with a face-on view, the brightest such object in the nearby universe. However, the detection needed very high spatial resolution in the infrared wavelengths, and at the same time, a large array of telescopes that is laid out suitably to observe objects at different orientations.

a) The same ring radii with the fitted thin-ring model shown in dotted line. The inner dashed–solid line indicates the polar axis as probed by the optical polarization, and the outer dashed–solid line segments show the PA of the radio jet. (b) HST/WFPC2 archival image of the narrow-line region in [O iii]5007 line, with the two sets of dashed–solid line segments corresponding to those in panel (a). (c) Three-dimensional distribution of [O iii]-emitting clouds reconstructed from HST/STIS multi-slit data, which cover the volume indicated by gray lines. For reference, the HST image from panel (b) in green is also shown at the back of the 3D cube, as the 2D flux distribution projected on to the sky plane.

The Georgia State University CHARA Array interferometer at the Mount Wilson Observatory in California is the only facility which meets both of these requirements. The Array consists of 6 telescopes, each of which has a 1-meter diameter mirror, that are combined to achieve the spatial resolution of a much larger telescope. While each individual telescope is relatively small, the array layout is optimized to observe objects in a variety of angles and with large distances between telescopes. This achieves a very high spatial resolution capability. The CHARA Array actually has the sharpest eyes in the world in infrared wavelengths. With the CHARA Array, the team finally detected the dusty ring, at a right angle to the emerging jet in the center of the galaxy called NGC 4151.

“We’ve been hoping to see this structure in a bare nucleus object for a long, long time,” says Makoto Kishimoto, principal investigator of the project at Kyoto Sangyo University.

A big boost was that each telescope has recently added a new system called “adaptive optics.” Matt Anderson, a postdoctoral researcher at the CHARA Array who played a critical role in conducting the observations, says “This greatly increased the injection rate of the light, compensating for the relatively small collecting mirror to observe the extragalactic target, which is much fainter than the stellar targets typically observed in our Galaxy.”

Schematic 3D geometry inferred for the central region.

Over the last nearly 40 years, researchers in the field believed that this dusty ring is a key to understanding different characteristics of accreting supermassive blackhole systems. The properties we observe depend on whether we have an obscured, edge-on view or clear, face-on view of the nucleus of the active galaxy. The detection of this ring-like structure validates this model.

Furthermore, the detection probably is not just an indication of a flat structure. Additional studies have been showing that the structure seen at slightly longer infrared wavelengths, corresponding to an even larger outer region, seems elongated along the jet, and not at a right angle to it. This has been interpreted as an indication for a dusty wind being blown out toward the jet direction. The present finding that the inner structure looks flat and perpendicular to the jet, is an important link to the windy structure and its interaction with the rest of the galaxy surrounding the active black hole system.

These groundbreaking observations measured the size and orientation of the dusty disk. The team is working to get an even more detailed image of the central region by building a new instrument at the CHARA Array that can see deeper into space and resolve finer scale structure of the source.

GW190521 as a dynamical capture of two nonspinning black holes

by R. Gamba, M. Breschi, G. Carullo, S. Albanesi, P. Rettegno, S. Bernuzzi, A. Nagar in Nature Astronomy

When black holes collide in the universe, the clash shakes up space and time: the amount of energy released during the merger is so great that it causes space-time to oscillate, similar to waves on the surface of water. These gravitational waves spread out through the entire universe and can still be measured thousands of light years away, as was the case on 21 May 2019, when the two gravitational wave observatories LIGO (USA) and Virgo (Italy) captured such a signal. Named GW190521 after the date of its discovery, the gravitational wave event has since provoked discussion among experts because it differs markedly from previously measured signals.

The signal had initially been interpreted to mean that the collision involved two black holes moving in near-circular orbits around each other. “Such binary systems can be created by a number of astrophysical processes,” explains Prof. Sebastiano Bernuzzi, a theoretical physicist from the University of Jena, Germany. Most of the black holes discovered by LIGO and Virgo, for example, are of stellar origin. “That means they are the remnants of massive stars in binary star systems,” adds Bernuzzi, who led the current study. Such black holes orbit each other in quasi-circular orbits, just as the original stars did previously.

Number of encounters as a function of the initial energy and angular momentum.

“GW190521 behaves significantly differently, however,” explains Rossella Gamba. The lead author of the publication is doing her doctorate in Jena Research Training Group 2522 and is part of Bernuzzi’s team. “Its morphology and explosion-like structure are very different from previous observations.”

So, Rossella Gamba and her colleagues set out to find an alternative explanation for the unusual gravitational wave signal. Using a combination of state-of-the-art analytical methods and numerical simulations on supercomputers, they calculated different models for the cosmic collision. They came to the conclusion that it must have occurred on a strongly eccentric path instead of a quasi-circular one. A black hole initially moves freely in an environment that is relatively densely filled with matter and, as soon as it gets close to another black hole, it can be “captured” by the other’s gravitational field. This also leads to the formation of a binary system, but here the two black holes do not orbit in a circle, but move eccentrically, in tumbling motions around each other.

“Such a scenario explains the observations much better than any other hypothesis presented so far. The probability is 1:4300,” says Matteo Breschi, doctoral student and co-author of the study, who developed the infrastructure for the analysis. And postdoctoral researcher Dr Gregorio Carullo adds: “Even though we don’t currently know exactly how common such dynamic movements by black holes are, we don’t expect them to be a frequent occurrence.” This makes the current results all the more exciting, he adds. Nevertheless, more research is needed to clarify beyond doubt the processes that created GW190521.

The Stellar Halo of the Galaxy is Tilted and Doubly Broken

by Jiwon Jesse Han, Charlie Conroy, Benjamin D. Johnson, Joshua S. Speagle, Ana Bonaca, Vedant Chandra, Rohan P. Naidu, Yuan-Sen Ting, Turner Woody, Dennis Zaritsky in The Astronomical Journal

A new study has revealed the true shape of the diffuse cloud of stars surrounding the disk of our galaxy. For decades, astronomers have thought that this cloud of stars — called the stellar halo — was largely spherical, like a beach ball. Now a new model based on modern observations shows the stellar halo is oblong and tilted, much like a football that has just been kicked.

The findings offer insights into a host of astrophysical subject areas. The results, for example, shed light on the history of our galaxy and galactic evolution, while also offering clues in the ongoing hunt for the mysterious substance known as dark matter.

“The shape of the stellar halo is a very fundamental parameter that we’ve just measured to greater accuracy than was possible before,” says study lead author Jiwon “Jesse” Han, a PhD student at the Center for Astrophysics | Harvard & Smithsonian. “There are a lot of important implications of the stellar halo not being spherical but instead shaped like a football, rugby ball, or zeppelin — take your pick!”

H3 Survey sky coverage as of 2022 May in Galactic coordinates.

“For decades, the general assumption has been that the stellar halo is more or less spherical and isotropic, or the same in every direction,” adds study co-author Charlie Conroy, Han’s advisor, and a professor of astronomy at Harvard University and the Center for Astrophysics. “We now know that the textbook picture of our galaxy embedded within a spherical volume of stars has to be thrown out.”

The Milky Way’s stellar halo is the visible portion of what is more broadly called the galactic halo. This galactic halo is dominated by invisible dark matter, whose presence is only measurable through the gravity that it exerts. Every galaxy has its own halo of dark matter. These halos serve as a sort of scaffold upon which ordinary, visible matter hangs. In turn, that visible matter forms stars and other observable galactic structure. To better understand how galaxies form and interact, as well as the underlying nature of dark matter, stellar haloes are accordingly valuable astrophysical targets.

“The stellar halo is a dynamic tracer of the galactic halo,” says Han. “In order to learn more about galactic haloes in general, and especially our own galaxy’s galactic halo and history, the stellar halo is a great place to start.”

Fathoming the shape of the Milky Way’s stellar halo, though, has long challenged astrophysicists for the simple reason that we are embedded within it. The stellar halo extends out several hundred thousand light years above and below the star-filled plane of our galaxy, where our Solar System resides.

“Unlike with external galaxies, where we just look at them and measure their halos,” says Han, “we lack the same sort of aerial, outside perspective of our own galaxy’s halo.”

Complicating matters further, the stellar halo has proven to be quite diffuse, containing only about one percent of the mass of all the galaxy’s stars. Yet over time, astronomers have succeeded in identifying many thousands of stars that populate this halo, which are distinguishable from other Milky Way stars due to their distinctive chemical makeup (gaugeable by studies of their starlight), as well as by their distances and motions across the sky. Through such studies, astronomers have realized that halo stars are not evenly distributed. The goal has since been to study the patterns of over-densities of stars — spatially appearing as bunches and streams — to sort out the ultimate origins of the stellar halo.

The new study by CfA researchers and colleagues leverages two major datasets gathered in recent years that have plumbed the stellar halo as never before. The first set is from Gaia, a revolutionary spacecraft launched by the European Space Agency in 2013. Gaia has continued compiling the most precise measurements of the positions, motions, and distances of millions of stars in the Milky Way, including some nearby stellar halo stars. The second dataset is from H3 (Hectochelle in the Halo at High Resolution), a ground-based survey conducted at the MMT, located at the Fred Lawrence Whipple Observatory in Arizona, and a collaboration between the CfA and the University of Arizona. H3 has gathered detailed observations of tens of thousands of stellar halo stars too far away for Gaia to assess.

Combining these data in a flexible model that allowed for the stellar halo shape to emerge from all the observations yielded the decidedly non-spherical halo — and the football shape nicely dovetails with other findings to date. The shape, for example, independently and strongly agrees with a leading theory regarding the formation of the Milky Way’s stellar halo. According to this framework, the stellar halo formed when a lone dwarf galaxy collided 7–10 billion years ago with our far-larger galaxy. The departed dwarf galaxy is amusingly known as Gaia-Sausage-Enceladus (GSE), where “Gaia” refers to the aforementioned spacecraft, “Sausage” for a pattern appearing when plotting the Gaia data and “Enceladus” for the Greek mythological giant who was buried under a mountain — rather like how GSE was buried in the Milky Way. As a consequence of this galactic collisional event, the dwarf galaxy was ripped apart and its constituent stars strewn out into a dispersed halo. Such an origin story accounts for the stellar halo stars’ inherent unlikeness to stars born and bred in the Milky Way.

Posterior distribution from fitting a mock data set constructed to resemble the H3 Survey. Blue lines indicate the sample mode, and red lines are the true value. The true parameters are all within the statistical uncertainty of the fit. We adopt a uniform prior for all fits. Breaking radii are in units of kiloparsec.

The study’s results further chronicle just how GSE and the Milky Way interacted all those eons ago. The football shape — technically called a triaxial ellipsoid — reflects the observations of two pileups of stars in the stellar halo. The pileups ostensibly formed when GSE went through two orbits of the Milky Way. During these orbits, GSE would have slowed down twice at so-called apocenters, or the furthest points in the dwarf galaxy’s orbit of the greater gravitational attractor, the hefty Milky Way; these pauses led to the extra shedding of GSE stars. Meanwhile, the tilt of the stellar halo indicates that GSE encountered the Milky Way at an incident angle and not straight-on.

“The tilt and distribution of stars in the stellar halo provide dramatic confirmation that our galaxy collided with another smaller galaxy 7–10 billion years ago,” says Conroy.

Notably, so much time has passed since the GSE-Milky Way smashup that the stellar halo stars would have been expected to dynamically settle into the classical, long-assumed spherical shape. The fact that they haven’t likely speaks to the broader galactic halo, the team says. This dark matter-dominated structure is itself probably askew, and through its gravity, is likewise keeping the stellar halo off-kilter.

“The tilted stellar halo strongly suggests that the underlying dark matter halo is also tilted,” says Conroy. “A tilt in the dark matter halo could have significant ramifications for our ability to detect dark matter particles in laboratories on Earth.”

Conroy’s latter point alludes to the multiple dark matter detector experiments now running and planned. These detectors could increase their chances of capturing an elusive interaction with dark matter if astrophysicists can adjudge where the substance is more heavily concentrated, galactically speaking. As Earth moves through the Milky Way, it will periodically encounter these regions of dense and higher-velocity dark matter particles, boosting odds of detection. The discovery of the stellar halo’s most plausible configuration stands to move many astrophysical investigations forward while filling in basic details about our place in the universe.

“These are such an intuitively interesting questions to ask about our galaxy: ‘What does the galaxy look like?’ and ‘What does the stellar halo look like?’,” says Han. “With this line of research and study in particular, we are finally answering those questions.”

Late delivery of exotic chromium to the crust of Mars by water-rich carbonaceous asteroids

by Ke Zhu, Martin Schiller, Lu Pan, Nikitha Susan Saji, Kirsten K. Larsen, Elsa Amsellem, Courtney Rundhaug, Paolo Sossi, Ingo Leya, Frederic Moynier, Martin Bizzarro in Science Advances

Mars is called the red planet. But once, it was actually blue and covered in water, bringing us closer to finding out if Mars had ever harboured life.

Most researchers agree that there has been water on Mars, but just how much water is still debated. Now a study from the University of Copenhagen shows that some 4.5 billion years ago, there was enough water for the entire planet to be covered in a 300-metre-deep ocean.

“At this time, Mars was bombarded with asteroids filled with ice. It happened in the first 100 million years of the planet’s evolution. Another interesting angle is that the asteroids also carried organic molecules that are biologically important for life,” says Professor Martin Bizzarro from the Centre for Star and Planet Formation.

In addition to water, the icy asteroids also brought biologically relevant molecules such as amino acids to the Red Planet. Amino acids are used when DNA and RNA form bases that contain everything a cell needs.

Chromium mass-independent isotope compositions (μ53Cr and μ54Cr) and Mg number.

The new study indicates that the oceans that covered the entire planet in water were at least 300 metres deep. They may have been up to one kilometre deep. In comparison, there is actually very little water on Earth, explains Martin Bizzarro.

“This happened within Mars’s first 100 million years. After this period, something catastrophic happened for potential life on Earth. It is believed that there was a gigantic collision between the Earth and another Mars-sized planet. It was an energetic collision that formed the Earth-Moon system and, as the same time, wiped out all potential life on Earth,” says Martin Bizzarro.

Therefore, the researchers have really strong evidence that conditions allowing the emergence of life were present on Mars long before Earth.

It was by means of a meteorite that is billions of years old that the researchers have been able to look into Mars’s past history. The meteorite was once part of Mars’s original crust and offers a unique insight into what happened at the time when the solar system was formed. The whole secret is hiding in the way Mars’s surface has been created — and of which the meteorite was once a part — because it is a surface that does not move. On Earth it is opposite. The tectonic plates are in perpetual motion and recycled in the planet’s interior.

“Plate tectonics on Earth erased all evidence of what happened in the first 500 million years of our planet’s history. The plates constantly move and are recycled back and destroyed into the interior of our planet. In contrast, Mars does not have plate tectonics such that planet’s surface preserves a record of the earliest history of the planet,” explains Martin Bizzarro.

Rapid formation of exoplanetesimals revealed by white dwarfs

by Amy Bonsor, Tim Lichtenberg, Joanna Dra̧żkowska, Andrew M. Buchan in Nature Astronomy

A team of astronomers have found that planet formation in our young Solar System started much earlier than previously thought, with the building blocks of planets growing at the same time as their parent star.

A study of some of the oldest stars in the Universe suggests that the building blocks of planets like Jupiter and Saturn begin to form while a young star is growing. It had been thought that planets only form once a star has reached its final size, but new results suggests that stars and planets ‘grow up’ together. The research, led by the University of Cambridge, changes our understanding of how planetary systems, including our own Solar System, formed, potentially solving a major puzzle in astronomy.

“We have a pretty good idea of how planets form, but one outstanding question we’ve had is when they form: does planet formation start early, when the parent star is still growing, or millions of years later?” said Dr Amy Bonsor from Cambridge’s Institute of Astronomy, the study’s first author.

To attempt to answer this question, Bonsor and her colleagues studied the atmospheres of white dwarf stars — the ancient, faint remnants of stars like our Sun — to investigate the building blocks of planet formation. The study also involved researchers from the University of Oxford, the Ludwig-Maximilians-Universität in Munich, the University of Groningen and the Max Planck Institute for Solar System Research, Gottingen.

“Some white dwarfs are amazing laboratories, because their thin atmospheres are almost like celestial graveyards,” said Bonsor.

Enrichment in Fe, Ni and Cr relative to Ca, Mg and Si of planetary materials accreted by white dwarfs suggests the accretion of core- or mantle-rich material.

Normally, the interiors of planets are out of reach of telescopes. But a special class of white dwarfs — known as ‘polluted’ systems — have heavy elements such as magnesium, iron, and calcium in their normally clean atmospheres. These elements must have come from small bodies like asteroids left over from planet formation, which crashed into the white dwarfs and burned up in their atmospheres. As a result, spectroscopic observations of polluted white dwarfs can probe the interiors of those torn-apart asteroids, giving astronomers direct insight into the conditions in which they formed.

Planet formation is believed to begin in a protoplanetary disc — made primarily of hydrogen, helium, and tiny particles of ices and dust — orbiting a young star. According to the current leading theory on how planets form, the dust particles stick to each other, eventually forming larger and larger solid bodies. Some of these larger bodies will continue to accrete, becoming planets, and some remain as asteroids, like those that crashed into the white dwarfs in the current study.

The researchers analysed spectroscopic observations from the atmospheres of 200 polluted white dwarfs from nearby galaxies. According to their analysis, the mixture of elements seen in the atmospheres of these white dwarfs can only be explained if many of the original asteroids had once melted, which caused heavy iron to sink to the core while the lighter elements floated on the surface. This process, known as differentiation, is what caused the Earth to have an iron-rich core.

“The cause of the melting can only be attributed to very short-lived radioactive elements, which existed in the earliest stages of the planetary system but decay away in just a million years,” said Bonsor. “In other words, if these asteroids were melted by something which only exists for a very brief time at the dawn of the planetary system, then the process of planet formation must kick off very quickly.”

The study suggests that the early-formation picture is likely to be correct, meaning that Jupiter and Saturn had plenty of time to grow to their current sizes.

“Our study complements a growing consensus in the field that planet formation got going early, with the first bodies forming concurrently with the star,” said Bonsor. “Analyses of polluted white dwarfs tell us that this radioactive melting process is a potentially ubiquitous mechanism affecting the formation of all extrasolar planets.
“This is just the beginning — every time we find a new white dwarf, we can gather more evidence and learn more about how planets form. We can trace elements like nickel and chromium and say how big an asteroid must have been when it formed its iron core. It’s amazing that we’re able to probe processes like this in exoplanetary systems.”

GOALS-JWST: Resolving the Circumnuclear Gas Dynamics in NGC 7469 in the Mid-infrared

by Vivian U, Thomas Lai, Marina Bianchin, Raymond P. Remigio, et al in The Astrophysical Journal Letters

First in line to receive data transmissions from the James Webb Space Telescope, a team of astronomers at the University of California, Irvine and other institutions is using the unprecedentedly clear observations to reveal the secret inner workings of galaxies.

In a paper, the researchers describe their examination of the nearby galaxy NGC 7469 with the JWST’s ultrasensitive mid-infrared detection instruments. They conducted the most detailed analysis yet of the interactions between an active galactic nucleus dominated by a supermassive black hole and the star-forming galaxy regions surrounding it.

“What we are seeing in this system has been a surprise for us,” said lead author Vivian U, UCI assistant research scientist in physics and astronomy and member of one of 13 JWST Early Release Science teams. “Viewing this galaxy face-on, we are able to see not only winds from the supermassive black hole blowing in our direction but also ‘shock heating’ of the gas induced by said winds very close to the central active galactic nucleus, which is something we had not expected to be able to discern so clearly.”

The distribution of flux (top; in log erg s−1 cm−2 pixel−1), velocity (middle; in km s−1), and velocity dispersion (bottom; in km s−1) for several bright emission lines in Ch1: [Fe ii] λ5.34 μm (left), H2 S(5) λ6.91 μm (middle), [Ar ii] λ6.99 μm (right).

U noted that shock heating happens when wind from a black hole in a galaxy’s center pushes on surrounding dense gas, creating a shock front that deposits energy into the interstellar medium. This effect could influence star formation in two opposing ways, she said. By compressing the gas into molecular form, it can foster the birth of new stars, or excessively strong feedback processes from the galactic wind can prevent birth by destroying stellar nurseries.

According to U, NGC 7469 is a Seyfert galaxy with an active center hosting a supermassive black hole and a ring of star-forming regions. For decades, astronomers have tried to study the detailed dynamics of these systems, which make up about 10 percent of all galaxies, but dust — commonly abundant at the center of them — has made that a challenge. The JWST gave U and her co-authors access to what lies behind the dust veil.

Using the telescope’s 6.5-meter mirror and advanced suite of tools, including the Mid-Infrared Instrument, the researchers were able to map several key ionized and molecular gas emission lines that inform astronomers about the conditions of the interstellar medium — the gas, dust and radiation that exist between star systems in a galaxy — pinpointing star-forming regions within a starburst ring. They also detected a high-velocity outflow of ionized gas that’s “blueshifted,” meaning it’s coming toward the observer versus traveling in the opposite direction.

“The newly realized capability of mid-infrared integral field spectroscopy from the JWST’s Mid-Infrared Instrument now allows us to see not just what’s there behind the dust but also how things are moving at very small scales that we couldn’t previously see at these wavelengths,” U said.
“We now have a more coherent picture — at least in this system — of how the active galactic nucleus is driving out gas and how that’s impacting the surrounding material,” she added. “We see definitive signs of the black hole-driven winds dumping energy out into the interstellar medium.”

(Top left) Extraction grid (cyan) overlaid on the Channel 1 flux image at 7.1 μm. Each extraction region is 06 on a side, capturing the inner ISM region in this 3 × 3 grid. The PSF FWHM is marked with a filled circle in the bottom-left corner. (Bottom) The Ch 1 short–medium–long stitched spectra extracted from the grid, each labeled by its direction relative to the center “cen.” Spectral features are labeled; the spectra are normalized at [Ar ii] λ6.99 μm for ease of comparison.

U said that a significant contributor to the roiling dynamics of NGC 7469 is the fact that it’s merging with a second galaxy.

“The interaction with another galaxy means that galactic materials are being moved around as a result of tidal forces, and they file toward the center of the galaxy system when angular momentum is lost. This process tends to make the galaxy center very dusty,” she explained. “That’s why you need instruments like the ones aboard the JWST that allow us to peer through the dust and facilitate our understanding of the dusty cores of merging galaxies.”

New Limit on Axionlike Dark Matter Using Cold Neutrons

by Ivo Schulthess, Estelle Chanel, Anastasio Fratangelo, Alexander Gottstein, Andreas Gsponer, Zachary Hodge, Ciro Pistillo, Dieter Ries, Torsten Soldner, Jacob Thorne, Florian M. Piegsa in Physical Review Letters

With the use of a precision experiment developed at the University of Bern, an international research team has succeeded in significantly narrowing the scope for the existence of dark matter. The experiment was carried out at the European Research Neutron Source at the Institute Laue-Langevin in France, and makes an important contribution to the search for these particles, of which little is known.

Cosmological observations of the orbits of stars and galaxies enable clear conclusions to be drawn about the attractive gravitational forces that act between the celestial bodies. The astonishing finding: visible matter is far from sufficient for being able to explain the development or movements of galaxies. This suggests that there exists another, so far unknown, type of matter. Accordingly, in the year 1933, the Swiss physicist and astronomer Fritz Zwicky inferred the existence of what is known now as dark matter. Dark matter is a postulated form of matter which isn’t directly visible but interacts via gravity, and consists of approximately five times more mass than the matter with which we are familiar.

Recently, following a precision experiment developed at the Albert Einstein Center for Fundamental Physics (AEC) at the University of Bern, an international research team succeeded in significantly narrowing the scope for the existence of dark matter. With more than 100 members, the AEC is one of the leading international research organisations in the field of particle physics.

Schematic of the experimental setup where a neutron beam enters from the left, polarized along the B0 field.

“What dark matter is actually made of is still completely unclear,” explains Ivo Schulthess, a PhD student at the AEC and the lead author of the study. What is certain, however, is that it is not made from the same particles that make up the stars, planet Earth or us humans. Worldwide, increasingly sensitive experiments and methods are being used to search for possible dark matter particles — until now, however, without success.

Certain hypothetical elementary particles, known as axions, are a promising category of possible candidates for dark matter particles. An important advantage of these extremely lightweight particles is that they could simultaneously explain other important phenomena in particle physics which have not yet been understood.

“Thanks to many years of expertise, our team has succeeded in designing and building an extremely sensitive measurement apparatus — the Beam EDM experiment,” explains Florian Piegsa, Professor for Low Energy and Precision Physics at the AEC, who was awarded one of the prestigious ERC Starting Grants from the European Research Council in 2016 for his research with neutrons. If the elusive axions actually exist, they should leave behind a characteristic signature in the measurement apparatus.

“Our experiment enables us to determine the rotational frequency of neutron spins, which move through a superposition of electric and magnetic fields,” explains Schulthess. The spin of each individual neutron acts as a kind of compass needle, which rotates due to a magnetic field similarly to the second hand of a wristwatch — but nearly 400,000 times faster.

“We precisely measured this rotational frequency and examined it for the smallest periodic fluctuations which would be caused by the interactions with the axions,” explains Piegsa. The results of the experiment were clear: “The rotational frequency of the neutrons remained unchanged, which means that there is no evidence of axions in our measurement,” says Piegsa.

The data for the top beam (blue upward triangle), the bottom beam (yellow downward triangle), and the difference between the two beams (red circle) are shown for various stages in the data processing.

Parameter space successfully narrowed down The measurements, which were carried out with researchers from France at the European Research Neutron Source at the Institute Laue-Langevin, allowed for the experimental exclusion of a previously completely unexplored parameter space of axions. It also proved possible to search for hypothetical axions which would be more than 1,000 times heavier than was previously possible with other experiments.

“Although the existence of these particles remains mysterious, we have successfully excluded an important parameter space of dark matter,” concludes Schulthess. Future experiments can now build on this work. “Finally answering the question of dark matter would give us a significant insight into the fundamentals of nature and take us a big step closer to a complete understanding of the universe,” explains Piegsa.

A Short Gamma-Ray Burst from a Protomagnetar Remnant

by N. Jordana-Mitjans, C. G. Mundell, C. Guidorzi, R. J. Smith, E. Ramírez-Ruiz, B. D. Metzger, S. Kobayashi, A. Gomboc, I. A. Steele, M. Shrestha, M. Marongiu, A. Rossi, B. Rothberg in The Astrophysical Journal

Gamma-ray bursts (GRBs) have been detected by satellites orbiting Earth as luminous flashes of the most energetic gamma-ray radiation lasting milliseconds to hundreds of seconds. These catastrophic blasts occur in distant galaxies, billions of light years from Earth.

A sub-type of GRB known as a short-duration GRB starts life when two neutron stars collide. These ultra-dense stars have the mass of our Sun compressed down to half the size of a city like London, and in the final moments of their life, just before triggering a GRB, they generate ripples in space-time — known to astronomers as gravitational waves.

Until now, space scientists have largely agreed that the ‘engine’ powering such energetic and short-lived bursts must always come from a newly formed black hole (a region of space-time where gravity is so strong that nothing, not even light, can escape from it). However, new research by an international team of astrophysicists, led by Dr Nuria Jordana-Mitjans at the University of Bath in the UK, is challenging this scientific orthodoxy. According to the study’s findings, some short-duration GRBs are triggered by the birth of a supramassive star (otherwise known as a neutron star remnant) not a black hole.

Dr Jordana-Mitjans said: “Such findings are important as they confirm that newborn neutron stars can power some short-duration GRBs and the bright emissions across the electromagnetic spectrum that have been detected accompanying them. This discovery may offer a new way to locate neutron star mergers, and thus gravitational waves emitters, when we’re searching the skies for signals.”

GRB 180618A light curves at the gamma-ray, X-ray, ultraviolet and optical bands.

Much is known about short-duration GRBs. They start life when two neutron stars, which have been spiralling ever closer, constantly accelerating, finally crash. And from the crash site, a jetted explosion releases the gamma-ray radiation that makes a GRB, followed by a longer-lived afterglow. A day later, the radioactive material that was expelled in all directions during the explosion produces what researchers call a kilonova. However, precisely what remains after two neutron stars collide — the ‘product’ of the crash — and consequently the power source that gives a GRB its extraordinary energy, has long been a matter of debate. Scientists may now be closer to resolving this debate, thanks to the findings of the Bath-led study.

Space scientists are split between two theories. The first theory has it that neutron stars merge to briefly form an extremely massive neutron star, only for this star to then collapse into a black hole in a fraction of a second. The second argues that the two neutron stars would result in a less heavy neutron star with a higher life expectancy. So the question that has been needling astrophysicists for decades is this: are short-duration GRBs powered by a black hole or by the birth of a long-lived neutron star? To date, most astrophysicists have supported the black hole theory, agreeing that to produce a GRB, it is necessary for the massive neutron star to collapse almost instantly.

From top to bottom: two-dimensional MODS-2 spectra of the galaxy G2 and the GRB 180618A host galaxy (G1), corresponding night-sky emission lines, and one-dimensional spectrum of the G1 galaxy.

Astrophysicists learn about neutron star collisions by measuring the electromagnetic signals of the resultant GRBs. The signal originating from a black hole would be expected to differ from that coming from a neutron star remnant. The electromagnetic signal from the GRB explored for this study (named GRB 180618A) made it clear to Dr Jordana-Mitjans and her collaborators that a neutron star remnant rather than a black hole must have given rise to this burst.

Elaborating, Dr Jordana-Mitjans said: “For the first time, our observations highlight multiple signals from a surviving neutron star that lived for at least one day after the death of the original neutron star binary.”

Professor Carole Mundell, study co-author and professor of Extragalactic Astronomy at Bath, where she holds the Hiroko Sherwin Chair in Extragalactic Astronomy, said: “We were excited to catch the very early optical light from this short gamma-ray burst — something that is still largely impossible to do without using a robotic telescope. But when we analysed our exquisite data, we were surprised to find we couldn’t explain it with the standard fast-collapse black hole model of GRBs.

“Our discovery opens new hope for upcoming sky surveys with telescopes such as the Rubin Observatory LSST with which we may find signals from hundreds of thousands of such long-lived neutron stars, before they collapse to become black holes.”

What initially puzzled the researchers was that the optical light from the afterglow that followed GRB 180618A disappeared after just 35 minutes. Further analysis showed that the material responsible for such a brief emission was expanding close to the speed of light due to some source of continuous energy that was pushing it from behind.

What was more surprising was that this emission had the imprint of a newborn, rapidly spinning and highly magnetised neutron star, called a millisecond magnetar. The team found that the magnetar after GRB 180618A was reheating the leftover material of the crash as it was slowing down.

Synthetic torpor protects rats from exposure to accelerated heavy ions

by Anggraeini Puspitasari, Fabio Squarcio, Martina Quartieri, et al in Scientific Reports

It is still a glimpse into the future: Astronauts could be put into artificial hibernation and in this state be better protected from cosmic radiation. At present, there are already promising approaches to follow up such considerations. An international research team led by the Biophysics Department of the GSI Helmholtzzentrum in Darmstadt now has found decisive indications of the possible benefits of artificial hibernation for radiation resistance. The research partners from Germany, Japan, Italy, the UK and the USA have recently published their results.

Scientists call the state, which hibernating animals enter, torpor. In this state, life-supporting functions of an organism are reduced: Body temperature is lowered, metabolism is reduced and body functions such as heart rate and respiration rate or oxygen uptake are significantly slowed down. At the molecular level, gene activity and protein biosynthesis are also reduced to a slower pace. In the study now published on synthetic torpor (i.e. a kind of artificially produced hibernation) and protection from ionizing radiation, the scientists demonstrated biological effects suggesting that synthetic torpor increases resistance to radiation. A proof that can be very useful in the long term for astronauts.

The 5′-AMP injection reduced activated microglia and maintained the number of resident macrophages.

Space radiation is acknowledged as one of the main health risks for human space exploration. Harmful effects of space radiation are a major challenge, especially for future long-term missions. The majority of radiation dose absorbed by crews in manned interplanetary missions is produced by galactic cosmic radiation (GCR), high-energy charged particles, including densely ionizing heavy ions, produced in distant galaxies. The energy of these particles is so high that shielding of the spacecraft cannot stop them and lead to exposure rates over 200 times higher than the radiation background on Earth over a very long period. For these reasons, radiation countermeasures for future missions are being investigated.

“The connections between torpor and radioresistance represent a highly innovative research approach. Our results indicate that synthetic torpor is a promising tool to enhance radioprotection in living organism during long-term space missions. It could thus be an effective strategy to protect humans as they explore the solar system,” summarizes Professor Marco Durante, Head of the GSI Biophysics Division.

It is already known that naturally hibernating animals acquire radioresistance in this state. However, the recent study is so significant because it is the first time that a hibernation-like biological state was induced in a non-hibernating animal (rat) and radioresistance to high-energy heavy ions could be proved. In experiments at Japan’s Gunma University Heavy-ion Medical Center, accelerated carbon ions were used to simulate radiation in space. The other in vitro cell experiments were performed at the GSI/FAIR campus in Darmstadt and were part of the FAIR Phase 0 experimental period.

The 5′-AMP administration in rats suppresses the radiation-induced liver damage.

The main results of the research team after irradiation and induction of a synthetic torpor proved the hypotheses: Synthetic hibernation may have protective effects on a lethal dose of C?ions. In addition, synthetic hibernation reduces the tissues damage from total body irradiation.

Furthermore, GSI scientists were able to characterize the underlying mechanism in their studies on rat tissue cells. They showed that lower oxygen concentration in the tissues (hypoxia) and reduced metabolism at low temperature (hypothermia) could be two important factors in the prevention of cell damage. The immunohistological analyses indicated that the synthetic torpor spares the tissue from energetic ion radiation. In addition, changes in metabolism at low temperatures could also affect DNA repair.

A lot of research is still needed to investigate and better understand the radioprotective effect of synthetic torpor in organs. Currently it is not possible technically to hibernate a human in a safe and controlled way. However, research is progressing. Only recently, the neuronal pathways that control torpor are been unraveled. Now the current publication adds another important component.

Fundamental Science and Engineering Questions in Planetary Cave Exploration

by J. Judson Wynne, Timothy N. Titus, Ali‐akbar Agha‐Mohammadi, et al in Journal of Geophysical Research: Planets

Is there life in Martian caves? It’s a good question, but it’s not the right question — yet. An international collaboration of scientists led by NAU researcher Jut Wynne has dozens of questions we need asked and answered. Once we figure out how to study caves on the Moon, Mars and other planetary bodies, then we can return to that question.

Wynne, an assistant research professor of cave ecology, is the lead author of two related studies, both published in a special collection of papers on planetary caves by the Journal of Geophysical Research Planets. The first, “Fundamental Science and Engineering Questions in Planetary Cave Research,” was done by an interdisciplinary team of 31 scientists, engineers and astronauts who produced a list of 198 questions that they, working with another 82 space and cave scientists and engineers, narrowed down to the 53 most important. Harnessing the knowledge of a considerable swath of the space science community, this work is the first study designed to identify the research and engineering priorities to advance the study of planetary caves. The team hopes their work will inform what will ultimately be needed to support robotic and human missions to a planetary cave — namely on the Moon and/or Mars. The second, “Planetary Caves: A Solar System View of Products and Processes,” was born from the first study. Wynne realized there had been no effort to catalog planetary caves across the solar system, which is another important piece of the big-picture puzzle. He assembled another team of planetary scientists to tackle that question.

Evaluation of potential bias of survey participants by professional specialty for the 31 survey participants in Survey 1.

“With the necessary financial investment and institutional support, the research and technological development required to achieve these necessary advancements over the next decade are attainable,” Wynne said. “We now have what I hope will become two foundational papers that will help propel planetary cave research from an armchair contemplative exercise to robots probing planetary subsurfaces.”

There are a lot of them. Scientists have identified at least 3,545 potential caves on 11 different moons and planets throughout the solar system, including the Moon, Mars and moons of Jupiter and Saturn. Cave formation processes have even been identified on comets and asteroids. If the surrounding environment allows for access into the subsurface, that presents an opportunity for scientific discovery that’s never been available before. The discoveries in these caves could be massive. Caves may one day allow scientists to “peer into the depths” of these rocky and icy bodies, which will provide insights into how they were formed (but also can provide further insights into how Earth was formed). They could also, of course, hold secrets of life.

“Caves on many planetary surfaces represent one of the best environments to search for evidence of extinct or perhaps extant lifeforms,” Wynne said. “For example, as Martian caves are sheltered from deadly surface radiation and violent windstorms, they are more likely to exhibit a more constant temperature regime compared to the surface, and some may even contain water ice. This makes caves on Mars one of the most important exploration targets in the search for life.”

And it’s not just finding life — these same factors make caves good locations for astronaut shelters on Mars and the Moon when crewed missions are able to explore.

“Radiation shielding will be essential for human exploration of the Moon and Mars,” said Leroy Chiao, a retired astronaut, former commander of the International Space Station and co-author of the first paper. “One possible solution is to utilize caves for this purpose. The requirements for astronaut habitats, EVA suits and equipment should take cave exploration and development into consideration, for protection from both solar and galactic cosmic radiation.”

Wynne, whose primary research is in terrestrial caves, said planetary cave research has long been a parallel research question to the earthly variety for nearly two decades. Caves support unique ecosystems that are sometimes quite divorced from the surface ecosystem in the same area. Who’s to say a cave on the Moon or Mars would not be similar? So, many questions he’s investigated about caves on Earth, he’s wondered how it could apply on other planets. He’s not the only one making the connection. Wynne has done multiple research projects with NASA to help advance detection technologies, and his modeling of cave habitats does not much care if a cave is terrestrial or extraterrestrial. There are enough similarities in the cave environment to make reasonable predictions that will factor prominently into the selection of cave targets for exploration.

“Tellurian caves at depth are often characterized by complete darkness, a stable temperature approximating the average annual surface temperature, low to no air flow and a near-water-saturated atmosphere,” he said. “The caves of other planetary bodies likely exhibit similar environmental conditions, but these will also be influenced by the surface conditions of the planetary body and the internal structure of the cave.”

Keith Cowing, editor of SpaceRef.com and NASAWatch.com, said using the existing infrastructure of a planet’s surface and subsurface may help humans get to other planets sooner than if we had to bring everything needed to survive with us.

“Humans have been living in caves for hundreds of thousands of years. Then they built their own when none were available,” he said. “As such, it is only natural to assume that caves will offer similar utility as humanity expands to other worlds. While planet-wide terraforming may be an end goal, the use of large, pre-existing structures such as caves and lava tubes may be a more practical way to bootstrap the technology to the maturity needed to tackle the surface of an entire planet.”

While much of this research is forward-looking, there’s also a need to consider what resources, research and support currently exist. Numerous robotic platforms and instrumentation suites are being tested, but the roadblock comes where it so often does — the lack of funding. With sufficient support, a robotic exploration mission to a lunar or Martian cave could be possible in the next five to 10 years. This research builds on past work to form a road map of sorts to move forward; Wynne sees it as a to-do list for that same process. The questions the scientists and engineers answered identify the tasks needed to prepare for that robotic exploration; it also looks even further ahead to the advancements needed in spacesuit technology, habitation modules and hardware that will enable humans to live and work safely underground on the Moon and Mars.

“This is an untapped area of inquiry in planetary science, and its importance in the search for life should not be overlooked,” he said. “In our lifetime, it is quite possible that we will peer into underground Mars to address the age-old question, ‘Does life exist beyond Earth?’”