ST/ Neutrino factories in deep outer space

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Paradigm

34 min readJul 20, 2022

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Space biweekly vol.56, 6th July — 20th July

TL;DR

Highly energetic and difficult to detect, neutrinos travel billions of light years before reaching our planet. Although it is known that these elementary particles come from the depths of our Universe, their precise origin is still unknown. Researchers are now shedding light on one aspect of this mystery: neutrinos are thought to be born in blazars, galactic nuclei fed by supermassive black holes.
An animated dive into the dusty Milky Way reveals the outlines of our galaxy taking shape as we look out further and further from Earth. Based on new data from an interactive tool that exploits data from the European Space Agency’s Gaia mission and other space science data sets, astronomers have created an animation to model dust in the Milky Way.
Astronomers have discovered a mysterious short-duration astronomical event that was as bright as a superluminous supernova, but evolving much faster.
New COMAP radio survey will peer beneath the ‘tip of the iceberg’ of galaxies to unveil a hidden era of star formation.
Astronomers detected a persistent radio signal from a far-off galaxy that appears to flash with surprising regularity. Named FRB 20191221A, this fast radio burst, or FRB, is currently the longest-lasting FRB, with the clearest periodic pattern, detected to date.
A team of physicists has developed a method for predicting the composition of dark matter — invisible matter detected only by its gravitational pull on ordinary matter and whose discovery has been long sought by scientists.
A newly discovered star only takes four years to travel around the black hole at the center of our galaxy.
In 2019, astronomers observed the nearest example to date of a star that was shredded, or ‘spaghettified,’ after approaching too close to a massive black hole. That tidal disruption of a sun-like star by a black hole 1 million times more massive than itself took place 215 million light years from Earth. Luckily, this was the first such event bright enough that astronomers could study the optical light from the stellar death, specifically the light’s polarization, to learn more about what happened after the star was torn apart.
When NASA’s OSIRIS-REx spacecraft arrived at the asteroid Bennu, scientists discovered something surprising: The asteroid’s surface wasn’t smooth like many were expecting but was covered in large boulders. Now, a team of physicists think they know why.
What do Mars and Iceland have in common? These days, not so much. But more than 4.5 billion years ago, it’s possible the Red Planet had a crust comparable to Iceland today. This discovery, hidden in the oldest martian fragments found on Earth, could provide information about our planet that was lost over billions of years of geological movement and could help explain why the Earth developed into a planet that sustains a broad diversity of life and Mars did not.
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

Space industry news

Latest research

Beginning a Journey Across the Universe: The Discovery of Extragalactic Neutrino Factories

by Sara Buson, Andrea Tramacere, Leonard Pfeiffer, Lenz Oswald, Raniere de Menezes, Alessandra Azzollini, Marco Ajell in The Astrophysical Journal Letters

Highly energetic and difficult to detect, neutrinos travel billions of light years before reaching our planet. Although it is known that these elementary particles come from the depths of our Universe, their precise origin is still unknown. An international research team, led by the University of Würzburg and the University of Geneva (UNIGE), is shedding light on one aspect of this mystery: neutrinos are thought to be born in blazars, galactic nuclei fed by supermassive black holes.

The Earth’s atmosphere is continuously bombarded by cosmic rays. These consist of electrically charged particles of energies up to 1020 electron volts. That is a million times more than the energy achieved in the world’s most powerful particle accelerator, the Large Hadron Collider near Geneva. The extremely energetic particles come from deep outer space, they have travelled billions of light years. Where do they originate, what shoots them through the Universe with such tremendous force? These questions are among the greatest challenges of astrophysics for over a century.

Cosmic rays’ birthplaces produce neutrinos. Neutrinos are neutral particles difficult to detect. They have almost no mass and hardly interact with matter. They race through the Universe and can travel through galaxies, planets and the human body almost without a trace. “Astrophysical neutrinos are produced exclusively in processes involving cosmic ray acceleration,” explains astrophysics Professor Sara Buson from Julius-Maximilians-Universität (JMU) Würzburg in Bavaria, Germany. This is precisely what makes these neutrinos unique messengers paving the way to pinpoint cosmic ray sources.

Pretrial p-value for the blazar/neutrino correlation as a function of the association radii rassoc, for neutrino data set with Lmin = [3.5, 4.0, 4.5]. The y-axis displays values on a logarithmic scale. The minimum chance probability of 3 × 10−7 is achieved with the set of parameters Lmin = 4.0 and rassoc = 055. The estimated posttrial chance probability is 6 × 10−7.

Despite the vast amount of data which astrophysicists have collected, the association of high-energy neutrinos with the astrophysical sources that originate them has been an unsolved problem for years. Sara Buson has always considered it a major challenge. It was in 2017 that the researcher and collaborators first brought a blazar (TXS 0506+056) into the discussion as a putative neutrino source in the journal Science. Blazars are active galactic nuclei powered by supermassive black holes that emit much more radiation than their entire galaxy. The publication sparked a scientific debate about whether there truly is a connection between blazars and high-energy neutrinos.

Following this first encouraging step, in June 2021 Prof. Buson’s group began an ambitious multi-messenger research project with the support of the European Research Council. This involves analysing various signals (“messengers,” e.g. neutrinos) from the Universe. The main goal is to shed light into the origin of astrophysical neutrinos, possibly establishing blazars as the first source of extragalactic high-energy neutrinos with high certainty. The project is now showing its first success: Sara Buson, along with her group, the former postdoc Raniere de Menezes (JMU) and with Andrea Tramacere from the University of Geneva, reports that blazars can be confidently associated with astrophysical neutrinos at an unprecedented degree of certainty.

All-sky map in equatorial coordinates (J2000) of the IceCube neutrino local p-value logarithms denoted as L. Locations of PeVatron blazars associated with neutrino hotspots are pointed out by black squares. For visualization clarity, the label of 5BZCat objects is limited to reporting the unique numerical coordinate part. Unassociated hotspots are highlighted by green squares. The location of TXS 0506+056 is shown for reference (green circle). Squares are not to scale and serve the only purpose of highlighting the blazars’ locations. The Galactic plane and Galactic center are shown for reference as a green line and star, respectively.

Andrea Tramacere is one of the experts in numerical modelling of acceleration processes and radiation mechanisms acting in relativistic jets — outflows of accelerated matter, approaching the speed of the light — in particular blazar jets. “The accretion process and the rotation of the black hole lead to the formation of relativistic jets, where particles are accelerated and emit radiation up to energies of a thousand billion of that of visible light! The discovery of the connection between these objects and the cosmic rays may be the ‘Rosetta stone’ of high-energy astrophysics!”

To arrive at these results, the research team utilized neutrino data from the IceCube Neutrino Observatory in Antarctica — the most sensitive neutrino detector currently in operation — and BZCat, one of the most accurate catalogues of blazars. “With this data, we had to prove that the blazars whose directional positions coincided with those of the neutrinos were not there by chance.” To do this, the UNIGE researcher developed a software capable of estimating how much the distributions of these objects in the sky look like the same. “After rolling the dice several times, we discovered that the random association can only exceed that of the real data once in a million trials! This is strong evidence that our associations are correct.”

Despite this success, the research team believes that this first sample of objects is only the ‘tip of the iceberg’. This work has enabled them to gather “new observational evidence,” which is the most important ingredient for building more realistic models of astrophysical accelerators. “What we need to do now is to understand what the main difference is between objects that emit neutrinos and those that do not. This will help us to understand the extent to which the environment and the accelerator ‘talk’ to each other. We will then be able to rule out some models, improve the predictive power of others and, finally, add more pieces to the eternal puzzle of cosmic ray acceleration!”

Updated Gaia-2MASS 3D maps of Galactic interstellar dust

by R. Lallement, J. L. Vergely, C. Babusiaux, N. L. J. Cox in Astronomy & Astrophysics

An animated dive into the dusty Milky Way reveals the outlines of our galaxy taking shape as we look out further and further from Earth.

Based on new data from an interactive tool that exploits data from the European Space Agency’s Gaia mission and other space science data sets, astronomers have created an animation to model dust in the Milky Way. The animation shows the cumulative build-up of dust looking from Earth’s local neighbourhood to ~13000 lightyears towards the galactic centre — around 10% of the overall distance across the Milky Way. Close by, dust swirls all around but, further out, the concentration of dust along the galactic plane becomes clear. Two ‘windows’, one above and one below the galactic plane, are also revealed.

“Dust clouds are related to the formation and death of stars, so their distribution tells a story of how structures formed in the galaxy and how the galaxy evolves,” said Nick Cox, coordinator of the EXPLORE project which is developing the tools. “The maps are also important for cosmologists in revealing regions where there is no dust and we can have a clear, unobstructed view out of the Milky Way to study the Universe beyond, such as to make Deep Field observations with Hubble or the new James Webb Space Telescope.”

De-reddened Hess diagram. The greyscale corresponds to the square root of the stellar density.

The tools used to create the animation combine data from the Gaia mission and the 2MASS All Sky Survey. The tools are part of a suite of applications designed to support studies of stars and galaxies, as well as lunar exploration, and have been developed through funding from the European Union’s Horizon 2020 Programme.

“State-of-the-art machine learning and visual analytics have the power to greatly enhance scientific return and discovery for space science missions, but their use is still relatively novel in the field of astronomy,” said Albert Zijlstra, of the University of Manchester and the EXPLORE project. “With a constant stream of new data, such as the recent third release of Gaia data in June 2022, we have an increasing wealth of information to mine — beyond the scope of what humans could process in a lifetime. We need tools like the ones we are developing for EXPLORE to support scientific discovery, such as by helping us to characterise properties within the data, or to pick out the most interesting or unusual features and structures.”

MUSSES2020J: The Earliest Discovery of a Fast Blue Ultraluminous Transient at Redshift 1.063

by Ji-an Jiang, Naoki Yasuda, Keiichi Maeda, Nozomu Tominaga, Mamoru Doi, et al in The Astrophysical Journal Letters

A team of astronomers have discovered a mysterious short-duration astronomical event, or transient, that is as bright as a superluminous supernova, but evolving much faster.

The universe is full of energetic transient phenomena, astronomical events that occur over a short period of time. For example, most massive stars end their lives by exploding spectacularly, known as a supernova, a major type of transients. In order to understand the origin of these transient phenomena, various time-domain surveys have been carried out in the past few decades. As more and more transients have been discovered, researchers began noticing some new transient types in recent years.

To figure out the nature of various transient phenomena, an international transient survey project called “MUltiband Subaru Survey for Early-phase Supernovae” (MUSSES), led by Ji-an Jiang, a former Kavli Institute for the Physics and Mathematics of the Universe (Kavli IPMU) Project Researcher (currently postdoctoral fellow at the National Astronomical Observatory of Japan (NAOJ)) attempt to catch various fast-evolving transients within one day of their occurrence, using the most powerful survey facility in the world, the Hyper Suprime-Cam (HSC) mounted on the 8.2-m Subaru telescope. By carrying out consecutive Subaru/HSC observations in December 2020, 20 fast-evolving transients have been discovered, and one of them, MUSSES2020J (AT 2020afay), caught Jiang’s attention.

Light curves of MUSSES2020J, FBUTs (Vinkó et al. 2015; Perley et al. 2019; Ho et al. 2020; Perley et al. 2021; here we classify Dougie as an FBUT due to the extremely high luminosity and fast light-curve decline in UV), SN 2018gep (Ho et al. 2019a), and normal FBOTs discovered by previous HSC and PS1 observations (broken lines; 3σ g-band nondetection limits are given as open triangles; Tanaka et al. 2016; Tampo et al. 2020; Drout et al. 2014). Light curves of some optically selected TDEs and candidates (Gezari et al. 2012; Arcavi et al. 2014; Blagorodnova et al. 2017) are plotted with transparent symbols for comparisons.

“MUSSES2020J was discovered with very low brightness on December 11 in 2020, and its brightness showed significant brightening during our observation. More surprisingly, the fast light curve evolution and very high redshift of the transient confirmed by follow-up observations indicate that the brightness of MUSSES2020J was about 50 times higher, while the rising phase was much shorter than those of normal supernovae, which indeed show high similarity to a recently discovered peculiar transient, AT 2018cow. We suggest calling these extreme transients as Fast Blue Ultraluminous Transient (FBUT). So far only a handful of them have been discovered, and we had never seen one soon after its occurrence due to their extremely fast evolution. Thanks to the high-cadence survey mode and the excellent performance of Subaru/HSC, we were able to perfectly catch this amazing phenomenon for the first time. The early multiband light-curve data bring some unique information to understand the origin of these amazing transients,” said first author Jiang.

The data has stimulated intensive discussion about the origins of MUSSES2020J and a few other FBUTs, led by various researchers within the team including Kyoto University graduate student Kohki Uno, Kyoto University Associate Professor Keiichi Maeda, NAOJ Assistant Professor Takashi Moriya, and Kavli IPMU Senior Scientist Ken’ichi Nomoto. The theoretical investigation is still ongoing, but the team has so far narrowed down the possibilities to a few scenarios, most of which involve an active compact object — either a black hole or a highly magnetized neutron star — to power these extremely bright objects.

Locations of MUSSES2020J and the nucleus of the host galaxy. Red spots are centers of the host galaxy measured from HSC SSP broadband images (*griz*).

“There is almost no doubt that an active compact object is involved, and it is a main reason why these transients are so different from normal supernovae. The remaining possibilities are an event where a star is tidally disrupted by a massive black hole, or a massive star collapse which is different from normal supernovae in a sense that it has probably left a highly active compact object like an accreting black hole. The very early-phase data provided for the first time for a class of FBUTs hints the existence of sub-relativistic outflow distinctly from a bulk of the slower ejecta, and this must be a key to solving the problem. We are currently checking the details of each model to robustly identify the origin of MUSSES2020J, with the strong constraint provided by this new observation,” said Maeda.

“MUSSES2020J shows a similar light curve of AT 2018cow. The light curve of AT 2018cow is well-reproduced by the model of interaction between circumstellar matter and the ejecta of a pulsational pair-instability supernova (PPISN). The PPISN is the explosion of a very massive star which would collapse to form a black hole and eject the outer layer in a jet-like form. Therefore, it is possible that a similar PPISN model with a different amount of circumstellar matter can also explain the light curve of MUSSES2020J,” Nomoto said.

Jiang’s team will continue looking for the answer of the origin of this newly confirmed transient type by carrying out transient surveys with telescopes all over the world.

“Thanks to the great capability of the Subaru Hyper Suprime-Cam, we could find a very rare mysterious transient. As the main target of our observation was different, we could not carry out follow-up observations well. It may be a failed explosion event of a star, or it may be related to a massive black hole. Next time, as we know we can find these events, we can prepare follow-up observations to understand this kind of mysterious event,” said Kavli IPMU Visiting Senior Scientist and University of Tokyo Professor Mamoru Doi.

COMAP Early Science. I. Overview

by Kieran A. Cleary, Jowita Borowska, Patrick C. Breysse, Morgan Catha, Dongwoo T. Chung, Sarah E. Church, Clive Dickinson, Hans Kristian Eriksen, et al in The Astrophysical Journal

Sometime around 400 million years after the birth of our universe, the first stars began to form. The universe’s so-called dark ages came to an end and a new light-filled era began. More and more galaxies began to take shape and served as factories for churning out new stars, a process that reached a peak about 4 billion years after the Big Bang.

Luckily for astronomers, this bygone era can be observed. Distant light takes time to reach us, and our telescopes can pick up light emitted by galaxies and stars billions of years ago (our universe is 13.8 billion years old). But the details of this chapter in our universe’s history are murky since most of the stars being formed are faint and hidden by dust. A new Caltech project, called COMAP (CO Mapping Array Project), will offer us a new glimpse into this epoch of galaxy assembly, helping to answer questions about what really caused the universe’s rapid increase in the production of stars.

Left: a simulated 2.5 deg2 field showing galaxy positions in gray (adapted from Kovetz et al. 2017). Center: simulated CO intensity map of the same field in a slice of 40 MHz bandwidth, corresponding to a redshift interval Δz = 0.004. The VLA would take about 4500 hr to cover the same area, but would detect just 1% of the galaxies (shown in red on the left). COMAP, on the other hand, is sensitive to the aggregate emission from all galaxies in the line of sight, including those too faint to detect individually. Right: a representative power spectrum for the intensity map shown in the center panel. The spectrum is composed of two components: one from the clustering of galaxies on large scales and a second that arises from the scale-independent shot noise, which dominates on small scales. The shaded region indicates schematically the scales to which the Pathfinder is most sensitive.

“Most instruments might see the tip of an iceberg when looking at galaxies from this period,” says Kieran Cleary, the project’s principal investigator and the associate director of Caltech’s Owens Valley Radio Observatory (OVRO). “But COMAP will see what lies underneath, hidden from view.”

The current phase of the project uses a 10.4-meter “Leighton” radio dish at OVRO to study the most common kinds of star-forming galaxies spread across space and time, including those that are too difficult to view in other ways because they are too faint or hidden by dust. The radio observations trace the raw material from which stars are made: cold hydrogen gas. This gas is not easy to pinpoint directly, so instead COMAP measures bright radio signals from carbon monoxide (CO) gas, which is always present along with the hydrogen. COMAP’s radio camera is the most powerful ever built to detect these radio signals. Based on observations taken one year into a planned five-year survey, COMAP set upper limits on how much cold gas must be present in galaxies at the epoch being studied, including the ones that are normally too faint and dusty to see. While the project has not yet made a direct detection of the CO signal, these early results demonstrate that it is on track to do so by the end of the initial five-year survey and ultimately will paint the most comprehensive picture yet of the universe’s history of star formation.

Redshift of the three lowest CO transition lines as a function of observed frequency. The frequency coverage for the COMAP Pathfinder Survey (26–34 GHz) is sensitive to the CO(1–0) line in the redshift range z = 2.4–3.4 and the CO(2–1) line at z = 6–8. Also shown is the frequency coverage of a future COMAP-*EoR* survey, in which a second frequency channel (12–20 GHz) is added, sensitive to the CO(1–0) line at z = 4.8–8.6.

“Looking to the future of the project, we aim to use this technique to successively look further and further back in time,” Cleary says. “Starting 4 billion years after the Big Bang, we will keep pushing back in time until we reach the epoch of the first stars and galaxies, a couple of billion years earlier.”

Anthony Readhead, the co-principal investigator and the Robinson Professor of Astronomy, Emeritus, says that COMAP will see the not only the first epoch of stars and galaxies, but also their epic decline. “We will observe star formation rising and falling like an ocean tide,” he says. COMAP works by capturing blurry radio images of clusters of galaxies over cosmic time rather than sharp images of individual galaxies. This blurriness enables the astronomers to efficiently catch all the radio light coming from a larger pool of galaxies, even the faintest and dustiest ones that have never been seen.

“In this way, we can find the average properties of typical, faint galaxies without needing to know very precisely where any individual galaxy is located,” explains Cleary. “This is like finding the temperature of a large volume of water using a thermometer rather than analyzing the motions of the individual water molecules.”

Sub-second periodicity in a fast radio burst

by The CHIME/FRB Collaboration., Andersen, B.C., Bandura, K. et al. in Nature

Astronomers at MIT and elsewhere have detected a strange and persistent radio signal from a far-off galaxy that appears to be flashing with surprising regularity.

The signal is classified as a fast radio burst, or FRB — an intensely strong burst of radio waves of unknown astrophysical origin, that typically lasts for a few milliseconds at most. However, this new signal persists for up to three seconds, about 1,000 times longer than the average FRB. Within this window, the team detected bursts of radio waves that repeat every 0.2 seconds in a clear periodic pattern, similar to a beating heart.

The researchers have labeled the signal FRB 20191221A, and it is currently the longest-lasting FRB, with the clearest periodic pattern, detected to date. The source of the signal lies in a distant galaxy, several billion light-years from Earth. Exactly what that source might be remains a mystery, though astronomers suspect the signal could emanate from either a radio pulsar or a magnetar, both of which are types of neutron stars — extremely dense, rapidly spinning collapsed cores of giant stars.

“There are not many things in the universe that emit strictly periodic signals,” says Daniele Michilli, a postdoc in MIT’s Kavli Institute for Astrophysics and Space Research. “Examples that we know of in our own galaxy are radio pulsars and magnetars, which rotate and produce a beamed emission similar to a lighthouse. And we think this new signal could be a magnetar or pulsar on steroids.”

The team hopes to detect more periodic signals from this source, which could then be used as an astrophysical clock. For instance, the frequency of the bursts, and how they change as the source moves away from Earth, could be used to measure the rate at which the universe is expanding. The discovery is authored by members of the CHIME/FRB Collaboration, including MIT co-authors Calvin Leung, Juan Mena-Parra, Kaitlyn Shin, and Kiyoshi Masui at MIT, along with Michilli, who led the discovery first as a researcher at McGill University, and then as a postdoc at MIT.

Radio signal from FRBs 20210206A and 20210213A.

Since the first FRB was discovered in 2007, hundreds of similar radio flashes have been detected across the universe, most recently by the Canadian Hydrogen Intensity Mapping Experiment, or CHIME, an interferometric radio telescope consisting of four large parabolic reflectors that is located at the Dominion Radio Astrophysical Observatory in British Columbia, Canada. CHIME continuously observes the sky as the Earth rotates, and is designed to pick up radio waves emitted by hydrogen in the very earliest stages of the universe. The telescope also happens to be sensitive to fast radio bursts, and since it began observing the sky in 2018, CHIME has detected hundreds of FRBs emanating from different parts of the sky.

The vast majority of FRBs observed to date are one-offs — ultrabright bursts of radio waves that last for a few milliseconds before blinking off. Recently, researchers discovered the first periodic FRB that appeared to emit a regular pattern of radio waves. This signal consisted of a four-day window of random bursts that then repeated every 16 days. This 16-day cycle indicated a periodic pattern of activity, though the signal of the actual radio bursts was random rather than periodic. On Dec. 21, 2019, CHIME picked up a signal of a potential FRB, which immediately drew the attention of Michilli, who was scanning the incoming data.

“It was unusual,” he recalls. “Not only was it very long, lasting about three seconds, but there were periodic peaks that were remarkably precise, emitting every fraction of a second — boom, boom, boom — like a heartbeat. This is the first time the signal itself is periodic.”

Periodicity analysis of FRBs 20210206A and 20210213A.

In analyzing the pattern of FRB 20191221A’s radio bursts, Michilli and his colleagues found similarities with emissions from radio pulsars and magnetars in our own galaxy. Radio pulsars are neutron stars that emit beams of radio waves, appearing to pulse as the star rotates, while a similar emission is produced by magnetars due to their extreme magnetic fields. The main difference between the new signal and radio emissions from our own galactic pulsars and magnetars is that FRB 20191221A appears to be more than a million times brighter. Michilli says the luminous flashes may originate from a distant radio pulsar or magnetar that is normally less bright as it rotates and for some unknown reason ejected a train of brilliant bursts, in a rare three-second window that CHIME was luckily positioned to catch.

“CHIME has now detected many FRBs with different properties,” Michilli says. “We’ve seen some that live inside clouds that are very turbulent, while others look like they’re in clean environments. From the properties of this new signal, we can say that around this source, there’s a cloud of plasma that must be extremely turbulent.”

The astronomers hope to catch additional bursts from the periodic FRB 20191221A, which can help to refine their understanding of its source, and of neutron stars in general.

“This detection raises the question of what could cause this extreme signal that we’ve never seen before, and how can we use this signal to study the universe,” Michilli says. “Future telescopes promise to discover thousands of FRBs a month, and at that point we may find many more of these periodic signals.”

Early crustal processes revealed by the ejection site of the oldest martian meteorite

by A. Lagain, S. Bouley, B. Zanda, K. Miljković, A. Rajšić, D. Baratoux, V. Payré, L. S. Doucet, N. E. Timms, R. Hewins, G. K. Benedix, V. Malarewic, K. Servis, P. A. Bland in Nature Communications

What do Mars and Iceland have in common? These days, not so much. But more than 4.5 billion years ago, it’s possible the Red Planet had a crust comparable to Iceland today. This discovery, hidden in the oldest martian fragments found on Earth, could provide information about our planet that was lost over billions of years of geological movement and could help explain why the Earth developed into a planet that sustains a broad diversity of life and Mars did not.

These insights into Earth’s past came out of a new study by an international team that includes an NAU researcher. The study details how they found the likely martian origin of the 4.48-billion-year-old meteorite, informally named Black Beauty. Its origin is one of the oldest regions of Mars.

“This meteorite recorded the first stage of the evolution of Mars and, by extension, of all terrestrial planets, including the Earth,” said Valerie Payré, a postdoctoral researcher in the Department of Astronomy and Planetary Science. “As the Earth lost its old surface mainly due to plate tectonics, observing such settings in extremely ancient terrains on Mars is a rare window into the ancient Earth surface that we lost a long time ago.”

Summary of NWA 7034 and paired stone radiometric ages, and chronology of major events experienced by the breccia.

The team, led by Anthony Lagain from Curtin University in Australia, searched for the location of origin of a martian meteorite (officially named NWA — Northwest Africa — 7034 for where it was found on Earth). This meteorite, the chemistry of which indicates that Mars had volcanic activity to that found on Earth, recorded the first stage of Mars’ evolution. Although it was ejected from the surface of Mars five to 10 million years ago after an asteroid impact, its source region and geological context has remained a mystery.

This team studied chemical and physical properties of Black Beauty to pinpoint where it came from; they determined it was from Terra Cimmeria-Sirenum, one of the most ancient regions of Mars. It may have a surface similar to Earth’s continents. Planetary bodies like Mars have impacts craters all over their surface, so finding the right one is challenging. In a previous study, Lagain’s team developed a crater detection algorithm that uses high-resolution images of the surface of Mars to identify small impact craters, finding about 90 million as small as 50 meters in diameter. In this study, they were able to isolate the most plausible ejection site — the Karratha crater that excavated ejecta of an older crater named Khujirt.

The NWA 7034 launch site geological context.

“For the first time, we know the geological context of the only brecciated Martian sample available on Earth, 10 years before the NASA’s Mars Sample Return mission is set to send back samples collected by the Perseverance rover currently exploring the Jezero crater,” said Lagain, a research fellow in the School of Earth and Planetary Sciences at Curtin. “This research paved the way to locate the ejection site of other Martian meteorites, in order to create the most exhaustive view of the Red Planet’s geological history.”

Payré studies the nature and formation of Mars’ crust to determine if Earth and Mars share a common past that include both a continent-like and ocean-like crust. She uses orbital observations captured in this region to investigate whether traces of volcanism similar to Iceland exist on Mars.

“As of today, Mars’ crust complexity is not understood, and knowing about the origin of these amazing ancient fragments could lead future rover and spatial missions to explore the Terra Sirenum-Cimmeria region that hides the truth of Mars’ evolution, and perhaps the Earth’s,” she said. “This work paves the road to locate the ejection site of other martian meteorites that will provide the most exhaustive view of the geological history of Mars and will answer one of the most intriguing questions: why Mars, now dry and cold, evolved so differently from Earth, a flourishing planet for life?”

The team’s algorithm is adapted to detect impact craters constellating Mercury and the Moon, the other terrestrial bodies. This can be used to help unravel their geographical history and answer foundational questions regarding their formation and evolution. This work is a starting point to guide future investigations of the Solar System.

Joint Cosmic Microwave Background and Big Bang Nucleosynthesis Constraints on Light Dark Sectors with Dark Radiation

by Cara Giovanetti, Mariangela Lisanti, Hongwan Liu, Joshua T. Ruderman in Physical Review Letters

A team of physicists has developed a method for predicting the composition of dark matter — invisible matter detected only by its gravitational pull on ordinary matter and whose discovery has been long sought by scientists.

The work centers on predicting “cosmological signatures” for models of dark matter with a mass between that of the electron and the proton. Previous methods had predicted similar signatures for simpler models of dark matter. This research establishes new ways to find these signatures in more complex models, which experiments continue to search for, the paper’s authors note.

“Experiments that search for dark matter are not the only way to learn more about this mysterious type of matter,” says Cara Giovanetti, a Ph.D. student in New York University’s Department of Physics and the lead author of the paper.
“Precision measurements of different parameters of the universe — for example, the amount of helium in the universe, or the temperatures of different particles in the early universe — can also teach us a lot about dark matter,” adds Giovanetti, outlining the method.

The allowed region of dark matter mass mχ and ΔNν, for a complex scalar particle and a dark photon with mass 3mχ.

In the research, conducted with Hongwan Liu, an NYU postdoctoral fellow, Joshua Ruderman, an associate professor in NYU’s Department of Physics, and Princeton physicist Mariangela Lisanti, Giovanetti and her co-authors focused on big bang nucleosynthesis (BBN) — a process by which light forms of matter, such as helium, hydrogen, and lithium, are created. The presence of invisible dark matter affects how each of these elements will form. Also vital to these phenomena is the cosmic microwave background (CMB) — electromagnetic radiation, generated by combining electrons and protons, that remained after the universe’s formation. The team sought a means to spot the presence of a specific category of dark matter — that with a mass between that of the electron and the proton — by creating models that took into account both BBN and CMB.

“Such dark matter can modify the abundances of certain elements produced in the early universe and leave an imprint in the cosmic microwave background by modifying how quickly the universe expands,” Giovanetti explains.

In its research, the team made predictions of cosmological signatures linked to the presence of certain forms of dark matter. These signatures are the result of dark matter changing the temperatures of different particles or altering how fast the universe expands. Their results showed that dark matter that is too light will lead to different amounts of light elements than what astrophysical observations see.

“Lighter forms of dark matter might make the universe expand so fast that these elements don’t have a chance to form,” says Giovanetti, outlining one scenario. “We learn from our analysis that some models of dark matter can’t have a mass that’s too small, otherwise the universe would look different from the one we observe,” she adds.

Spectropolarimetry of the tidal disruption event AT 2019qiz: a quasispherical reprocessing layer

by Kishore C Patra, Wenbin Lu, Thomas G Brink, Yi Yang, Alexei V Filippenko, Sergiy S Vasylyev in Monthly Notices of the Royal Astronomical Society

In 2019, astronomers observed the nearest example to date of a star that was shredded, or “spaghettified,” after approaching too close to a massive black hole.

That tidal disruption of a sun-like star by a black hole 1 million times more massive than itself took place 215 million light years from Earth. Luckily, this was the first such event bright enough that astronomers from the University of California, Berkeley, could study the optical light from the stellar death, specifically the light’s polarization, to learn more about what happened after the star was torn apart.

Their observations on Oct. 8, 2019, suggest that a lot of the star’s material was blown away at high speed — up to 10,000 kilometers per second — and formed a spherical cloud of gas that blocked most of the high-energy emissions produced as the black hole gobbled up the remainder of the star. Earlier, other observations of optical light from the blast, called AT2019qiz, revealed that much of the star’s matter was launched outward in a powerful wind. But the new data on the light’s polarization, which was essentially zero at visible or optical wavelengths when the event was at its brightest, tells astronomers that the cloud was likely spherically symmetric.

“This is the first time anyone has deduced the shape of the gas cloud around a tidally spaghetiffied star,” said Alex Filippenko, UC Berkeley professor of astronomy and a member of the research team.

The results support one answer to why astronomers don’t see high-energy radiation, such as X-rays, from many of the dozens of tidal disruption events observed to date: The X-rays, which are produced by material ripped from the star and dragged into an accretion disk around the black hole before falling inward, are obscured from view by the gas blown outward by powerful winds from the black hole.

“This observation rules out a class of solutions that have been proposed theoretically and gives us a stronger constraint on what happens to gas around a black hole,” said UC Berkeley graduate student Kishore Patra, lead author of the study. “People have been seeing other evidence of wind coming out of these events, and I think this polarization study definitely makes that evidence stronger, in the sense that you wouldn’t get a spherical geometry without having a sufficient amount of wind. The interesting fact here is that a significant fraction of the material in the star that is spiraling inward doesn’t eventually fall into the black hole — it’s blown away from the black hole.”

Many theorists have hypothesized that the stellar debris forms an eccentric, asymmetric disk after disruption, but an eccentric disk is expected to show a relatively high degree of polarization, which would mean that perhaps several percent of the total light is polarized. This was not observed for this tidal disruption event.

“One of the craziest things a supermassive black hole can do is to shred a star by its enormous tidal forces,” said team member Wenbin Lu, UC Berkeley assistant professor of astronomy. “These stellar tidal disruption events are one of very few ways astronomers know the existence of supermassive black holes at the centers of galaxies and measure their properties. However, due to the extreme computational cost in numerically simulating such events, astronomers still do not understand the complicated processes after a tidal disruption.”

A second set of observations on Nov. 6, 29 days after the October observation, revealed that the light was very slightly polarized, about 1%, suggesting that the cloud had thinned enough to reveal the asymmetric gas structure around the black hole. Both observations came from the 3-meter Shane telescope at Lick Observatory near San Jose, California, that is fitted with the Kast spectrograph, an instrument that can determine the polarization of light over the full optical spectrum. The light becomes polarized — its electrical field vibrates primarily in one direction — when it scatters off electrons in the gas cloud.

“The accretion disk itself is hot enough to emit most of its light in X-rays, but that light has to come through this cloud, and there are many scatterings, absorptions and reemissions of light before it can escape out of this cloud,” Patra said. “With each of these processes, the light loses some of its photon energy, going all the way down to ultraviolet and optical energies. The final scatter then determines the polarization state of the photon. So, by measuring polarization, we can deduce the geometry of the surface where the final scatter happens.”

Patra noted that this deathbed scenario may apply only to normal tidal disruptions — not “oddballs,” in which relativistic jets of material are expelled out the poles of the black hole. Only more measurements of the polarization of light from these events will answer that question.

“Polarization studies are very challenging, and very few people are well-versed enough in the technique around the world to utilize this,” he said. “So, this is uncharted territory for tidal disruption events.”

Patra, Filippenko, Lu and UC Berkeley researcher Thomas Brink, graduate student Sergiy Vasylyev and postdoctoral fellow Yi Yang reported their observations. The UC Berkeley researchers calculated that the polarized light was emitted from the surface of a spherical cloud with a radius of about 100 astronomical units (au), 100 times farther from the star than Earth is from the sun. An optical glow from hot gas emanated from a region at about 30 au. The 2019 spectropolarimetric observations — a technique that measures polarization across many wavelengths of light — were of AT2019qiz, a tidal disruption located in a spiral galaxy in the constellation of Eridanus. The zero polarization of the entire spectrum in October indicates a spherically symmetric cloud of gas — all the polarized photons balance one another. The slight polarization of the November measurements indicates a small asymmetry. Because these tidal disruptions occur so far away, in the centers of distant galaxies, they appear as only a point of light, and polarization is one of few indications of the shapes of objects.

“These disruption events are so far away that you can’t really resolve them, so you can’t study the geometry of the event or the structure of these explosions,” Filippenko said. “But studying polarized light actually helps us to deduce some information about the distribution of the matter in that explosion or, in this case, how the gas — and possibly the accretion disk — around this black hole is shaped.”

Fine-grained regolith loss on sub-km asteroids

by Hsiang-Wen Hsu, Xu Wang, Anthony Carroll, Noah Hood, Mihály Horányi in Nature Astronomy

Like corn kernels popping in a frying pan, tiny grains of dust may hop around on the surface of asteroids, according to a new study from physicists at the University of Colorado Boulder.

That popcorn-like effect may even help to tidy up smaller asteroids, causing them to lose dust and look rough and craggy from space. The findings may help scientists better understand how asteroids change shape over time — and how these bodies migrate through space, sometimes bringing them dangerously close to Earth, said Hsiang-Wen (Sean) Hsu, lead author of the study.

“The more fine-grained material, or regolith, these asteroids lose, the faster they migrate,” said Hsu, a research associate at the Laboratory for Atmospheric and Space Physics (LASP) at CU Boulder.

The research began with a few curious photos. In 2020, a NASA spacecraft named OSIRIS-REx traveled more than 1 billion miles to rendezvous with the asteroid (191055) Bennu, which is about as tall as the Empire State Building. But when the spacecraft arrived, scientists didn’t find what they were expecting: The asteroid’s surface looked like rough sandpaper, not smooth and dusty like researchers had predicted. There were even large boulders scattered over its exterior. Now, Hsu and his colleagues have drawn on computer simulations, or models, and laboratory experiments to explore that puzzle. He said that forces akin to static electricity may be kicking the smallest grains of dust, some no bigger than a single bacterium, off the asteroid and into space — leaving only larger rocks behind. Bennu isn’t alone, said study co-author Mihály Horányi.

“We’re realizing that these same physics are occurring on other airless bodies like the moon and even the rings of Saturn,” said Horányi, a researcher at LASP and professor of physics at CU Boulder.

Regolith Size Distribution Evolution Modeling.

Asteroids might look like they’re frozen in time, but these bodies evolve throughout their lifetimes. Hsu explained that asteroids like Bennu are constantly spinning, which exposes their surfaces to sunlight, then shadow and sunlight again. That never-ending cycle of heating and cooling puts a strain on the largest rocks at the surface, until they inevitably crack.

“It’s happening every day, all the time,” Hsu said. “You wind up eroding a big piece of rock into smaller pieces.”

Which is why, before scientists arrived at Bennu, many were expecting to find it covered in smooth sand — a bit like how the moon looks today. Not long before, a Japanese space mission landed on a second small asteroid called Ryugu. The team found a similarly rough and craggy terrain. Hsu and his colleagues were suspicious. Since the 1990s, researchers at LASP have used vacuum chambers in the lab to investigate the strange properties of dust in space, including a feat they call “electrostatic lofting.” Study co-lead author Xu Wang explained that as the sun’s rays bathe small grains of dust, they begin to pick up negative charges. Those charges will build until, suddenly, the particles burst apart, like two magnets repelling each other. In some cases, those grains of dust can pop away at speeds of more than 20 miles per hour (or more than 8 meters per second).

“No one had ever considered this process on the surface of an asteroid before,” said Wang, a research associate at LASP.

Size distribution of electrostatically lofted particles from laboratory experiments.

To do that, the researchers, including former CU Boulder undergraduate students Anthony Carroll and Noah Hood, ran a series of calculations examining the physics of regolith on two hypothetical asteroids. They tracked how dust might form, then hop around over hundreds of thousands of years. One of those faux asteroids was about a half-mile across (similar in size to Ryugu) and the second several miles wide (closer in diameter to big asteroids like Eros). The size made a difference. According to the team’s estimates, when grains of dust jumped on the bigger asteroid, they couldn’t gain enough speed to break free of its gravity. The same wasn’t true on the smaller, Ryugu-like asteroid.

“The gravity on the smaller asteroid is so weak that it can’t hold back the escape,” Hsu said. “The fine-grained regolith will be lost.”

That lost dust, in turn, will expose the surface of the asteroids to even more erosion, leading to a boulder-rich scenery like scientists found on Ryugu and Bennu. Within several million years, in fact, the smaller asteroid was almost completely swept clean of fine dust. The Eros-like asteroid, however, stayed dusty. Hsu noted that this scrubbing effect could help to give the orbits of small asteroids a nudge. He explained that asteroids migrate because the sun’s radiation pushes on them slowly over time. Based on previous research by other scientists, he suspects that asteroids covered in boulders may move faster than those with a dustier appearance. He and his colleagues may soon get more proof to back up their calculations. In less than 3 months, a NASA mission called the Double Asteroid Redirection Test (DART) will visit a pair of smaller asteroids — and Hsu will be watching to see how dusty they are.

“We will have new surface images to test our theory,” he said. “It’s nice for us, but also a little nerve-wracking.”

Observation of S4716 — a Star with a 4 yr Orbit around Sgr A*

by Florian Peißker, Andreas Eckart, Michal Zajaček, Silke Britzen in The Astrophysical Journal

Researchers at the University of Cologne and Masaryk University in Brno (Czech Republic) have discovered the fastest known star, which travels around a black hole in record time. The star, S4716, orbits Sagittarius A*, the black hole in the centre of our Milky Way, in four years and reaches a speed of around 8000 kilometres per second. S4716 comes as close as 100 AU (astronomical unit) to the black hole — a small distance by astronomical standards. One AU corresponds to 149,597,870 kilometres.

In the vicinity of the black hole at the centre of our galaxy is a densely packed cluster of stars. This cluster, called S cluster, is home to well over a hundred stars that differ in their brightness and mass. S stars move particularly fast.

‘One prominent member, S2, behaves like a large person sitting in front of you in a movie theatre: it blocks your view of what’s important,’ said Dr Florian Peissker, lead author of the new study. ‘The view into the centre of our galaxy is therefore often obscured by S2. However, in brief moments we can observe the surroundings of the central black hole.’

The K-band view of the GC observed with NIRC2 (Keck) in 2019.30. This image is high-pass filtered and shows the position of several S stars close to Sgr A*, which is indicated by a black cross.

By means of continuously refining methods of analysis, together with observations covering almost twenty years, the scientist now identified without a doubt a star that travels around the central supermassive black hole in just four years. A total of five telescopes observed the star, with four of these five being combined into one large telescope to allow even more accurate and detailed observations. ‘For a star to be in a stable orbit so close and fast in the vicinity of a supermassive black hole was completely unexpected and marks the limit that can be observed with traditional telescopes,’ said Peissker. Moreover, the discovery sheds new light on the origin and evolution of the orbit of fast-moving stars in the heart of the Milky Way.

‘The short-period, compact orbit of S4716 is quite puzzling,’ Michael Zajaček, an astrophysicist at Masaryk University in Brno who was involved in the study, said. ‘Stars cannot form so easily near the black hole. S4716 had to move inwards, for example by approaching other stars and objects in the S cluster, which caused its orbit to shrink significantly,’ he added.