ST/ Milky Way’s black hole: Rapid spin creates football-shaped spacetime
Space biweekly vol.92, 6th February — 23rd February
TL;DR
- The supermassive black hole at the Milky Way’s center spins rapidly, distorting spacetime into a football-like shape, revealing a speed estimated at 60% of its limit.
- Hydrothermal or metamorphic activity within the Kuiper Belt’s icy dwarf planets Eris and Makemake is indicated by methane on their surfaces, differing from comet methane.
- Mars displays diverse volcanic activity due to early crust recycling (vertical tectonics), providing insights into ancient crusts on Mars and Earth.
- Astronomers explain the gap in exoplanet size distribution at around two Earth radii by simulating the migration of icy sub-Neptunes toward the central star, altering their appearance.
- Cassini data reveals a global ocean beneath the icy shell of Saturn’s moon Mimas, formed 5–15 million years ago, suggesting potential life-supporting conditions on seemingly inactive moons.
- James Webb Space Telescope data suggests black holes at the universe’s dawn birthed stars and fueled galaxy formation.
- A molecular gas outflow from a quasar in the early universe confirms theoretical predictions, shedding light on cosmic evolution.
- Earth-like planets with a carbon monoxide (CO)-runaway gap in their atmospheres may indicate habitability, as CO is crucial for prebiotic organic compound formation.
- Theoretical physicists propose a gravastar solution to general relativity, envisioning these objects as Russian matryoshka dolls with one inside another.
- Advanced telescopes may enhance the search for extraterrestrial life by scrutinizing nearby exoplanets’ atmospheres, according to new research.
- And more!
Space industry in numbers
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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.
Latest research
New black hole spin values for Sagittarius A* obtained with the outflow method
by Ruth A Daly, Megan Donahue, Christopher P O’Dea, Biny Sebastian, Daryl Haggard, Anan Lu in Monthly Notices of the Royal Astronomical Society
The supermassive black hole in the center of the Milky Way is spinning so quickly it is warping the spacetime surrounding it into a shape that can look like a football, according to a new study using data from NASA’s Chandra X-ray Observatory and the U.S. National Science Foundation’s Karl G. Jansky Very Large Array (VLA). That football shape suggests the black hole is spinning at a substantial speed, which researchers estimated to be about 60% of its potential limit.
Astronomers call this giant black hole Sagittarius A* (Sgr A*). It is located about 26,000 light-years away from Earth in the center of the galaxy. To determine how quickly Sgr A* is spinning — one of its fundamental properties, along with mass — the researchers applied a method that uses X-ray and radio data to assess how material is flowing towards and away from the black hole. The work is led by Penn State Berks Professor of Physics Ruth Daly.
“Our work may help settle the question of how fast our galaxy’s supermassive black hole is spinning,” Daly said. “Our results indicate that Sgr A* is spinning very rapidly, which is interesting and has far-reaching implications.”
The team found the angular velocity — the number of revolutions per second — of Sgr A*’s spin is about 60% of the maximum possible value, a limit set because material cannot travel faster than the speed of light. Past estimations of Sgr A*’s speed have been made with different techniques and by other astronomers, with results ranging from no rotation at all to spinning at almost the maximum rate.
“This work, however, shows that this could change if the amount of material in the vicinity of Sgr A* increases,” Daly said.
As a black hole rotates, it pulls “spacetime” — the combination of time and the three dimensions of space — and nearby matter. The gravitational pull also squashes the spacetime, altering its shape depending on how it’s observed. Spacetime appears circular if the black hole is viewed from the top. From the side, however, the spacetime is shaped like a football. The faster the spin, the flatter the football.
The spin can also serve as an energy source, Daly said, if matter — such as gas or the remnants of a star that wanders too close — exists in the vicinity of the black hole. As the black hole spins, matter can escape in the form of narrow jets called collimated outflows. However, Sgr A* currently has limited nearby matter, so the black hole has been relatively quiet, with weakly collimated outflows, in recent millennia.
“A spinning black hole is like a rocket on the launch pad,” said Biny Sebastian, a co-author from the University of Manitoba in Winnipeg, Canada. “Once material gets close enough, it’s like someone has fueled the rocket and hit the ‘launch’ button.”
This means that in the future, if the properties of the matter and the magnetic field strength close to the black hole change, part of the enormous energy of the black hole’s spin could drive more powerful outflows. This source material could come from gas or from the remnants of a star torn apart by the black hole’s gravity if that star wanders too close to Sgr A*.
“Jets powered and collimated by a galaxy’s spinning central black hole can profoundly affect the gas supply for an entire galaxy, which affects how quickly and even whether stars can form,” said co-author Megan Donahue from Michigan State University. “The ‘Fermi bubbles’ seen in X-rays and gamma rays around our Milky Way’s black hole show the black hole was probably active in the past. Measuring the spin of our black hole is an important test of this scenario.”
Fermi bubbles refer to structures that emit gamma rays above and below the black hole that researchers have theorized resulted from prior massive outflows. The researchers used the outflow method to determine the spin of Sgr A*. Daly’s approach incorporates consideration of the relationship between the spin of the black hole and its mass, the properties of the matter near the black hole and the outflow properties. The collimated outflow produces the radio waves, while the disk of gas surrounding the black hole emits X-rays. The researchers combined observational data from Chandra and the VLA with an independent estimate of the black hole’s mass from other telescopes to inform the outflow method and determine the black hole’s spin.
“We have a special view of Sgr A* because it is the nearest supermassive black hole to us,” said co-author Anan Lu from McGill University in Montreal, Canada. “Although it’s quiet right now, our work shows that in the future it will give an incredibly powerful kick to surrounding matter. That might happen in a thousand or a million years, or it could happen in our lifetimes.”
Moderate D/H ratios in methane ice on Eris and Makemake as evidence of hydrothermal or metamorphic processes in their interiors: Geochemical analysis
by Christopher R. Glein, William M. Grundy, Jonathan I. Lunine, Ian Wong, Silvia Protopapa, Noemi Pinilla-Alonso, John A. Stansberry, Bryan J. Holler, Jason C. Cook, Ana Carolina Souza-Feliciano in Icarus
A team co-led by Southwest Research Institute found evidence for hydrothermal or metamorphic activity within the icy dwarf planets Eris and Makemake, located in the Kuiper Belt. Methane detected on their surfaces has the tell-tale signs of warm or even hot geochemistry in their rocky cores, which is markedly different than the signature of methane from a comet.
“We see some interesting signs of hot times in cool places,” said SwRI’s Dr. Christopher Glein, an expert in planetary geochemistry and lead author of a paper about this discovery.
The Kuiper Belt is a vast donut-shaped region of icy bodies beyond the orbit of Neptune at the edge of the solar system. Eris and Makemake are comparable in size to Pluto and its moon Charon. These bodies likely formed early in the history of our solar system, about 4.5 billion years ago. Far from the heat of our Sun, KBOs were believed to be cold, dead objects. Newly published work from JWST studies made the first observations of isotopic molecules on the surfaces of Eris and Makemake. These so-called isotopologues are molecules that contain atoms having a different number of neutrons. They provide data that are useful in understanding planetary evolution.
The JWST team measured the composition of the dwarf planets’ surfaces, particularly the deuterium (heavy hydrogen, D) to hydrogen (H) ratio in methane. Deuterium is believed to have formed in the Big Bang, and hydrogen is the most abundant nucleus in the universe. The D/H ratio on a planetary body yields information about the origin, geologic history and formation pathways of compounds containing hydrogen.
“The moderate D/H ratio we observed with JWST belies the presence of primordial methane on an ancient surface. Primordial methane would have a much higher D/H ratio,” Glein said.
“Instead, the D/H ratio points to geochemical origins for methane produced in the deep interior. The D/H ratio is like a window. We can use it in a sense to peer into the subsurface. Our data suggest elevated temperatures in the rocky cores of these worlds so that methane can be cooked up. Molecular nitrogen (N2) could be produced as well, and we see it on Eris. Hot cores could also point to potential sources of liquid water beneath their icy surfaces.”
Over the past two decades, scientists have learned that icy worlds can be much more internally evolved than once believed. Evidence for subsurface oceans has been found at several icy moons such as Saturn’s moon Enceladus and Jupiter’s moon Europa. Liquid water is one of the key ingredients in determining potential planetary habitability. The possibility of water oceans inside Eris and Makemake is something that scientists are going to study in the years ahead. If either of them is habitable, then it would become the most distant world in the solar system that could possibly support life. Finding chemical indicators of internally driven processes takes them a step in this direction.
“If Eris and Makemake hosted, or perhaps could still host warm, or even hot, geochemistry in their rocky cores, cryovolcanic processes could then deliver methane to the surfaces of these planets, perhaps in geologically recent times,” said Dr. Will Grundy, an astronomer at Lowell Observatory, one of Glein’s co-authors and lead author of a companion paper. “We found a carbon isotope ratio (13C/12C) that suggests relatively recent resurfacing.”
This work is part of a paradigm shift in planetary science. It is increasingly being recognized that cold, icy worlds may be warm at heart. Models developed for this study additionally point to the formation of geothermal gases on Saturn’s moon Titan, which also has abundant methane. Furthermore, the inference of unexpected activity on Eris and Makemake underscores the importance of internal processes in shaping what we see on large KBOs and is consistent with findings at Pluto.
“After the New Horizons flyby of the Pluto system, and with this discovery, the Kuiper Belt is turning out to be much more alive in terms of hosting dynamic worlds than we would have imagined,” said Glein. “It’s not too early to start thinking about sending a spacecraft to fly by another one of these bodies to place the JWST data into a geologic context. I believe that we will be stunned by the wonders that await!”
Diverse volcanism and crustal recycling on early Mars
by Joseph R. Michalski, A. Deanne Rogers, Christopher S. Edwards, Aster Cowart, Long Xiao in Nature Astronomy
Volcanoes are a common feature on the surfaces of solid planets within the solar system, resulting from magmatic activity occurring within the planetary crust. On Earth, volcanism is driven primarily by heat and crustal recycling associated with plate tectonics, but Mars lacks plate tectonics and the driver of volcanism is not well understood.
Recent research by Professor Joseph MICHALSKI, a geologist in the Department of Earth Sciences at The University of Hong Kong (HKU), has revealed intriguing insights into the volcanic activity on Mars. He proposes that Mars has significantly more diverse volcanism than previously realised, driven by an early form of crust recycling called vertical tectonics. The findings shed light on the ancient crust of Mars and its potential implications for understanding early crustal recycling on both Mars and Earth.
Traditionally, Mars has been known to have large shield volcanoes similar to those in Hawaii. However, it was not known that Mars also possessed the diverse, explosive volcanoes that form on Earth due to crustal recycling. The recent research conducted by Professor Michalski and his international team discover a vast number of diverse volcanoes in the ancient crust of Mars.
‘We have known for decades that Mars has volcanoes, but most of the recognised volcanoes correspond to large basaltic shield volcanoes similar to the ones that make up Hawaii,’ he explains.
‘In this work, we show that the ancient crust has many other types of volcanoes such as lava domes, stratovolcanoes, calderas and large shields of ash, not lava. Further, most scientists see Mars as a planet composed of basalt, which has low silica content and represents little crustal evolution, but these volcanoes have high silica content which means they formed from a complex process of magma evolution not known before.’
The paper suggests that intense volcanism occurred on ancient Mars, causing the crust to collapse into the mantle, where the rocks re-melted, resulting in magmas that have high silica. This tectonic process, called vertical tectonics, is hypothesised to have occurred on the ancient Earth, but rocks on Earth from that period (the Archean, more than 3 billion years ago) are highly modified by later geological activity, so we cannot see evidence for this process clearly on this planet. Therefore, exploring other planets like Mars, which has volcanism but no plate tectonics, can help reveal the mysteries of early crustal recycling on both the Red Planet, and by analogy, on early Earth.
Professor Michalski concluded, ‘Mars contains critical geological puzzle pieces that help us understand not only that planet, but the Earth as well. Martian volcanism is much more complex and diverse than has been previously thought.’
‘This is a significant discovery because it has revealed that crustal recycling can occur not only in plate tectonic regimes dominated by horizontal movements, but can also occur in pre-plate tectonic regimes dominated by vertical movements. This finding can help earth scientists revolve the long-term controversial issues of how and when felsic continents formed in our planet (Earth)’, said Professor Guochun ZHAO, the Chair Professor of HKU Earth Sciences.
A radius valley between migrated steam worlds and evaporated rocky cores
by Remo Burn, Christoph Mordasini, Lokesh Mishra, Jonas Haldemann, Julia Venturini, Alexandre Emsenhuber, Thomas Henning in Nature Astronomy
Astronomers from Germany and Switzerland have uncovered evidence of how the enigmatic gap in the size distribution of exoplanets at around two Earth radii emerges. Their computer simulations demonstrate that the migration of icy, so-called sub-Neptunes into the inner regions of their planetary systems could account for this phenomenon. As they draw closer to the central star, evaporating water ice forms an atmosphere that makes the planets appear larger than in their frozen state. Simultaneously, smaller rocky planets gradually lose a portion of their original gaseous envelope, causing their measured radius to shrink over time.
Ordinarily, planets in evolved planetary systems, such as the Solar System, follow stable orbits around their central star. However, many indications suggest that some planets might depart from their birthplaces during their early evolution by migrating inward or outward. This planetary migration might also explain an observation that has puzzled researchers for several years: the relatively low number of exoplanets with sizes about twice as large as Earth, known as the radius valley or gap. Conversely, there are many exoplanets smaller and larger than this size.
“Six years ago, a reanalysis of data from the Kepler space telescope revealed a shortage of exoplanets with sizes around two Earth radii,” Remo Burn explains, an exoplanet researcher at the Max Planck Institute for Astronomy (MPIA) in Heidelberg.
“In fact, we — like other research groups — predicted based on our calculations, even before this observation, that such a gap must exist,” explains co-author Christoph Mordasini, a member of the National Centre of Competence in Research (NCCR) PlanetS. He heads the Division of Space Research and Planetary Sciences at the University of Bern. This prediction originated during his tenure as a scientist at MPIA, which has been jointly researching this field with the University of Bern for many years.
The most commonly suggested mechanism to explain the emergence of such a radius valley is that planets might lose a part of their original atmosphere due to the irradiation from the central star — especially volatile gases like hydrogen and helium. “However, this explanation neglects the influence of planetary migration,” Burn clarifies. It has been established for about 40 years that under certain conditions, planets can move inward and outward through planetary systems over time. How effective this migration is and to what extent it influences the development of planetary systems impacts its contribution to forming the radius valley.
Two different types of exoplanets inhabit the size range surrounding the gap. On one hand, there are rocky planets, which can be more massive than Earth and are hence called super-Earths. On the other hand, astronomers are increasingly discovering so-called sub-Neptunes (also mini-Neptunes) in distant planetary systems, which are, on average, slightly larger than the super-Earths.
“However, we do not have this class of exoplanets in the Solar System,” Burn points out. “That’s why, even today, we’re not exactly sure about their structure and composition.”
Still, astronomers broadly agree that these planets possess significantly more extended atmospheres than rocky planets. Consequently, understanding how these sub-Neptunes’ characteristics contribute to the radius gap has been uncertain. Could the gap even suggest that these two types of worlds form differently?
“Based on simulations we already published in 2020, the latest results indicate and confirm that instead, the evolution of sub-Neptunes after their birth significantly contributes to the observed radius valley,” concludes Julia Venturini from Geneva University. She is a member of the PlanetS collaboration mentioned above and led the 2020 study.
In the icy regions of their birthplaces, where planets receive little warming radiation from the star, the sub-Neptunes should indeed have sizes missing from the observed distribution. As these presumably icy planets migrate closer to the star, the ice thaws, eventually forming a thick water vapour atmosphere. This process results in a shift in planet radii to larger values. After all, the observations employed to measure planetary radii cannot differentiate whether the determined size is due to the solid part of the planet alone or an additional dense atmosphere. At the same time, as already suggested in the previous picture, rocky planets ‘shrink’ by losing their atmosphere. Overall, both mechanisms produce a lack of planets with sizes around two Earth radii.
“The theoretical research of the Bern-Heidelberg group has already significantly advanced our understanding of the formation and composition of planetary systems in the past,” explains MPIA Director Thomas Henning. “The current study is, therefore, the result of many years of joint preparatory work and constant improvements to the physical models.”
The latest results stem from calculations of physical models that trace planet formation and subsequent evolution. They encompass processes in the gas and dust disks surrounding young stars that give rise to new planets. These models include the emergence of atmospheres, the mixing of different gases, and radial migration.
“Central to this study were the properties of water at pressures and temperatures occurring inside planets and their atmospheres,” explains Burn. Understanding how water behaves over a wide range of pressures and temperatures is crucial for simulations. This knowledge has been of sufficient quality only in recent years. It is this component which permits realistic calculation of the sub-Neptunes’ behaviour, hence explaining the manifestation of extensive atmospheres in warmer regions.
“It’s remarkable how, as in this case, physical properties on molecular levels influence large-scale astronomical processes such as the formation of planetary atmospheres,” Henning adds.
“If we were to expand our results to cooler regions, where water is liquid, this might suggest the existence of water worlds with deep oceans,” Mordasini says. “Such planets could potentially host life and would be relatively straightforward targets for searching for biomarkers thanks to their size.”
A recently formed ocean inside Saturn’s moon Mimas
by V. Lainey, N. Rambaux, G. Tobie, N. Cooper, Q. Zhang, B. Noyelles, K. Baillie in Nature
Hidden beneath the heavily cratered surface of Mimas, one of Saturn’s smallest moons, lies a secret: a global ocean of liquid water. This astonishing discovery, led by Dr. Valéry Lainey of the Observatoire de Paris-PSL, reveals a “young” ocean formed just 5 to 15 million years ago, making Mimas a prime target for studying the origins of life in our Solar System.
“Mimas is a small moon, only about 400 kilometers in diameter, and its heavily cratered surface gave no hint of the hidden ocean beneath,” says Dr Nick Cooper, a co-author of the study and Honorary Research Fellow in the Astronomy Unit of the School of Physical and Chemical Sciences at Queen Mary University of London.
“This discovery adds Mimas to an exclusive club of moons with internal oceans, including Enceladus and Europa, but with a unique difference: its ocean is remarkably young, estimated to be only 5 to 15 million years old.”
This young age, determined through detailed analysis of Mimas’s tidal interactions with Saturn, suggests the ocean formed recently, based on the discovery of an unexpected irregularity in its orbit. As a result, Mimas provides a unique window into the early stages of ocean formation and the potential for life to emerge.
“The existence of a recently formed liquid water ocean makes Mimas a prime candidate for study, for researchers investigating the origin of life,” explains Dr Cooper.
The discovery was made possible by analysing data from NASA’s Cassini spacecraft, which meticulously studied Saturn and its moons for over a decade. By closely examining the subtle changes in Mimas’s orbit, the researchers were able to infer the presence of a hidden ocean and estimate its size and depth.
Dr Cooper continues: “This has been a great team effort, with colleagues from five different institutions and three different countries coming together under the leadership of Dr Valéry Lainey to unlock another fascinating and unexpected feature of the Saturn system, using data from the Cassini mission.”
The discovery of Mimas’s young ocean has significant implications for our understanding of the potential for life beyond Earth. It suggests that even small, seemingly inactive moons can harbor hidden oceans capable of supporting life-essential conditions. This opens up exciting new avenues for future exploration, potentially leading us closer to answering the age-old question: are we alone in the universe?
Which Came First: Supermassive Black Holes or Galaxies? Insights from JWST
by Joseph Silk, Mitchell C. Begelman, Colin Norman, Adi Nusser, Rosemary F. G. Wyse in The Astrophysical Journal Letters
Black holes not only existed at the dawn of time, they birthed new stars and supercharged galaxy formation, a new analysis of James Webb Space Telescope data suggests.
The insights upend theories of how black holes shape the cosmos, challenging classical understanding that they formed after the first stars and galaxies emerged. Instead, black holes might have dramatically accelerated the birth of new stars during the first 50 million years of the universe, a fleeting period within its 13.8 billion — year history.
“We know these monster black holes exist at the center of galaxies near our Milky Way, but the big surprise now is that they were present at the beginning of the universe as well and were almost like building blocks or seeds for early galaxies,” said lead author Joseph Silk, a professor of physics and astronomy at Johns Hopkins University and at Institut of Astrophysics, Paris, Sorbonne University.
“They really boosted everything, like gigantic amplifiers of star formation, which is a whole turnaround of what we thought possible before — so much so that this could completely shake up our understanding of how galaxies form.”
Distant galaxies from the very early universe, observed through the Webb telescope, appear much brighter than scientists predicted and reveal unusually high numbers of young stars and supermassive black holes, Silk said. Conventional wisdom holds that black holes formed after the collapse of supermassive stars and that galaxies formed after the first stars lit up the dark early universe. But the analysis by Silk’s team suggests that black holes and galaxies coexisted and influenced each other’s fate during the first 100 million years. If the entire history of the universe were a 12-month calendar, those years would be like the first days of January, Silk said.
“We’re arguing that black hole outflows crushed gas clouds, turning them into stars and greatly accelerating the rate of star formation,” Silk said. “Otherwise, it’s very hard to understand where these bright galaxies came from because they’re typically smaller in the early universe. Why on earth should they be making stars so rapidly?”
Black holes are regions in space where gravity is so strong that nothing can escape their pull, not even light. Because of this force, they generate powerful magnetic fields that make violent storms, ejecting turbulent plasma and ultimately acting like enormous particle accelerators, Silk said. This process, he said, is likely why Webb’s detectors have spotted more of these black holes and bright galaxies than scientists anticipated.
“We can’t quite see these violent winds or jets far, far away, but we know they must be present because we see many black holes early on in the universe,” Silk explained.
“These enormous winds coming from the black holes crush nearby gas clouds and turn them into stars. That’s the missing link that explains why these first galaxies are so much brighter than we expected.”
Silk’s team predicts the young universe had two phases. During the first phase, high-speed outflows from black holes accelerated star formation, and then, in a second phase, the outflows slowed down. A few hundred million years after the big bang, gas clouds collapsed because of supermassive black hole magnetic storms, and new stars were born at a rate far exceeding that observed billions of years later in normal galaxies, Silk said. The creation of stars slowed down because these powerful outflows transitioned into a state of energy conservation, he said, reducing the gas available to form stars in galaxies.
“We thought that in the beginning, galaxies formed when a giant gas cloud collapsed,” Silk explained. “The big surprise is that there was a seed in the middle of that cloud — a big black hole — and that helped rapidly turn the inner part of that cloud into stars at a rate much greater than we ever expected. And so the first galaxies are incredibly bright.”
The team expects future Webb telescope observations, with more precise counts of stars and supermassive black holes in the early universe, will help confirm their calculations. Silk expects these observations will also help scientists piece together more clues about the evolution of the universe.
“The big question is, what were our beginnings? The sun is one star in 100 billion in the Milky Way galaxy, and there’s a massive black hole sitting in the middle, too. What’s the connection between the two?” he said. “Within a year we’ll have so much better data, and a lot of our questions will begin to get answers.”
Molecular Outflow in the Reionization-epoch Quasar J2054–0005 Revealed by OH 119 μm Observations
by Dragan Salak, Takuya Hashimoto, Akio K. Inoue, Tom J. L. C. Bakx, Darko Donevski, Yoichi Tamura, Yuma Sugahara, Nario Kuno, Yusuke Miyamoto, Seiji Fujimoto, Suphakorn Suphapolthaworn in The Astrophysical Journal
Theoretical predictions have been confirmed with the discovery of an outflow of molecular gas from a quasar when the Universe was less than a billion years old.
A quasar is a compact region powered by a supermassive black hole located in the center of a massive galaxy. They are extremely luminous, with a point-like appearance similar to stars, and are extremely distant from Earth. Owing to their distance and brightness, they provide a peek into conditions of the early Universe, when it was less than 1 billion years old.
A team of researchers led by Assistant Professor Dragan Salak at Hokkaido University, Assistant Professor Takuya Hashimoto at the University of Tsukuba, and Professor Akio Inoue at Waseda University, has discovered the first evidence of suppression of star formation driven by an outflow of molecular gas in a quasar-host galaxy in the early Universe. Their findings, based on observations they made using the Atacama Large Millimeter/submillimeter Array (ALMA), in Chile.
Molecular gas is vital to the formation of stars. As the primary fuel of star formation, the ubiquity and high concentrations of molecular gas within a galaxy would lead to a vast number of stars being formed. By ejecting this gas into intergalactic space faster than it could be consumed by star formation, molecular outflows effectively suppress the formation of stars in galaxies that host quasars.
“Theoretical work suggests that molecular gas outflows play an important role in the formation and evolution of galaxies from an early age, because they can regulate star formation,” Salak explains. “Quasars are especially energetic sources, so we expected that they may be able to generate powerful outflows.”
The quasar the researchers observed, J2054–0005, has a very high redshift — it and the Earth are apparently moving away from each other very fast.
“J2054–0005 is one of the brightest quasars in the distant Universe, so we decided to target this object as an excellent candidate to study powerful outflows,” Hashimoto says.
The researchers used ALMA to observe the outflow of molecular gas from the quasar. As the only telescope in the world that has the sensitivity and frequency coverage to detect molecular gas outflows in the early Universe, ALMA was key to this study.
Speaking about the method used in the study, Salak comments: “The outflowing molecular (OH) gas was discovered in absorption. This means we did not observe microwave radiation coming directly from the OH molecules; instead, we observed the radiation coming from the bright quasar — and absorption means that OH molecules happened to absorb a part of the radiation from the quasar. So, it was like revealing the presence of a gas by seeing the ‘shadow’ it cast in front of the light source.”
Relative Abundances of CO2, CO, and CH4 in Atmospheres of Earth-like Lifeless Planets
by Yasuto Watanabe, Kazumi Ozaki in The Astrophysical Journal
A carbon monoxide (CO)-runaway gap identified in the atmospheres of Earth-like planets by researchers at Tokyo Tech can help expand the search for habitable planets. This gap, identified through atmospheric modeling, is an indicator of a CO-rich atmosphere on Earth-like planets orbiting Sun-like stars. CO is an important compound for the formation of prebiotic organic compounds, which are building blocks for more complex molecules for the formation of life.
The search for habitable exoplanets involves looking for planets with similar conditions to the Earth, such as liquid water, a suitable temperature range and atmospheric conditions. One crucial factor is the planet’s position in the habitable zone, the region around a star where liquid water could potentially exist on the planet’s surface. NASA’s Kepler telescope, launched in 2009, revealed that 20–50% of visible stars may host such habitable Earth-sized rocky planets. However, the presence of liquid water alone does not guarantee a planet’s habitability.
On Earth, carbon compounds such as carbon dioxide (CO2), methane (CH4), and carbon monoxide (CO) played a crucial role in shaping the climate and biogeochemistry and could have contributed to the emergence of life. Taking this into consideration, a recent study by Associate Professor Kazumi Ozaki from Tokyo Institute of Technology, along with Associate Researcher Yasuto Watanabe from The University of Tokyo, aims to expand the search for habitable planets. Researchers used atmospheric modeling to identify conditions that could result in a CO-rich atmosphere on Earth-like planets that orbit sun-like (F-, G-, and K-type) stars. This phenomenon, known as CO runaway, is suggested by atmospheric models to have possibly occurred in early planetary atmospheres, potentially favoring the emergence of life.
“The possibility of CO runaway is critical in resolving the fundamental problem regarding the origin of life on Earth because various organic compounds suitable for the prebiotic chemistry are more likely to form in a CO-rich atmosphere than in a CO2-rich atmosphere,” explains Dr. Ozaki.
The researchers modeled the CO cycle between the atmosphere and the oceans, considering the various sources of CO production, its transport mechanisms and the processes involved in its removal. The photolysis of CO2, in which CO2 breaks down into CO when exposed to light, was considered the primary source of CO. Additional sources included photochemical reactions in the atmosphere, emissions from volcanic gases, and the hydrothermal decomposition of formaldehyde (H2CO) in the ocean.
The removal of CO from the atmosphere primarily occurred through its reaction with hydroxyl (OH) radicals formed due to the photolysis of water vapor, and to a lesser extent, by deposition to the planet’s surface. The researchers found that a CO runaway occurs when the CO production surpasses the removal by OH radicals. This can occur due to higher CO2 levels or the presence of reducing gases from volcanoes which compete for the OH radicals. At a temperature of 277 K, conditions for CO runaway are met when the partial pressure of CO2 exceeds 0.2 bar. However, at higher temperatures (300 K), a CO runaway needs even higher CO2 and volcanic gas levels due to increased water vapor in the atmosphere, which is a major source of OH radicals.
Once initiated, the CO levels in the atmosphere are limited only by surface deposition, where CO is deposited onto the planet’s surface. Notably, the changes in the CO, CO2 and CH4 levels before and after the runaway effect led to a gap reflected in the phase space defined by the ratios of their partial pressures (pCO/pCO2 and pCH4/pCO2). “Our results suggest that this CO-runaway gap is a general feature of Earth-like lifeless planets orbiting Sun-like stars, providing insights into the characteristics and potential habitability of exoplanets,” says Dr. Ozaki.
Although the exact conditions that lead to the emergence of life remain uncertain, discoveries like the CO-runaway gap provide valuable clues in our quest to find habitable planets that could facilitate the origin of life among nearly 40 billion Earth-size planets orbiting Sun-like stars in the Milky Way galaxy.
Nested solutions of gravitational condensate stars
by Daniel Jampolski, Luciano Rezzolla in Classical and Quantum Gravity
If gravitational condensate stars (or gravastars) actually existed, they would look similar to black holes to a distant observer. Two theoretical physicists at Goethe University Frankfurt have now found a new solution to Albert Einstein’s theory of general relativity, according to which gravitational stars could be structured like a Russian matryoshka doll, with one gravastar located inside another.
The interior of black holes remains a conundrum for science. In 1916, German physicist Karl Schwarzschild outlined a solution to Albert Einstein’s equations of general relativity, according to which the center of a black hole consists of a so-called singularity, a point at which space and time no longer exist. Here, the theory goes, all physical laws, including Einstein’s general theory of relativity, no longer apply; the principle of causality is suspended. This constitutes a great nuisance for science: after all, it means that no information can escape from a black hole beyond the so-called event horizon.
This could be a reason why Schwarzschild’s solution did not attract much attention outside the theoretical realm for a long time — that is, until the first candidate for a black hole was discovered in 1971, followed by the discovery of the black hole in the center of our Milky Way in the 2000s, and finally the first image of a black hole, captured by the Event Horizon Telescope Collaboration in 2019.
In 2001, Pawel Mazur and Emil Mottola proposed a different solution to Einstein’s field equations that led to objects which they called gravitational condensate stars, or gravastars. Contrary to black holes, gravastars have several advantages from a theoretical astrophysics perspective.
On the one hand, they are almost as compact as black holes and also exhibit a gravity at their surface that is essentially as strong as that of a black hole, hence resembling a black hole for all practical purposes. On the other hand, gravastars do not have an event horizon, that is, a boundary from within which no information can be sent out, and their core does not contain a singularity. Instead, the center of gravastars is made up of an exotic — dark — energy that exerts a negative pressure to the enormous gravitational force compressing the star.
The surface of gravastars is represented by a wafer-thin skin of ordinary matter, the thickness of which approaches zero. Theoretical physicists Daniel Jampolski and Prof. Luciano Rezzolla of Goethe University Frankfurt have now presented a solution to the field equations of general relativity that describes the existence of a gravastar inside another gravastar. They have given this hypothetical celestial object the name “nestar” (from the English “nested”).
Daniel Jampolski, who discovered the solution as part of his Bachelor’s thesis supervised by Luciano Rezzolla, says: “The nestar is like a matryoshka doll,” adding that, “our solution to the field equations allows for a whole series of nested gravastars.” Whereas Mazur and Mottola posit that the gravastar has a near infinite thin skin consisting of normal matter, the nestar’s matter-composed shell is somewhat thicker: “It’s a little easier to imagine that something like this could exist.”
Luciano Rezzolla, Professor of Theoretical Astrophysics at Goethe University, explains: “It’s great that even 100 years after Schwarzschild presented his first solution to Einstein’s field equations from the general theory of relativity, it’s still possible to find new solutions. It’s a bit like finding a gold coin along a path that has been explored by many others before. Unfortunately, we still have no idea how such a gravastar could be created. But even if nestars don’t exist, exploring the mathematical properties of these solutions ultimately helps us to better understand black holes.”
Detecting Biosignatures in Nearby Rocky Exoplanets Using High-contrast Imaging and Medium-resolution Spectroscopy with the Extremely Large Telescope
by Huihao Zhang, Ji Wang, Michael K. Plummer in The Astronomical Journal
The next generation of advanced telescopes could sharpen the hunt for potential extraterrestrial life by closely scrutinizing the atmospheres of nearby exoplanets, new research suggests.
The next generation of advanced telescopes could sharpen the hunt for potential extraterrestrial life by closely scrutinizing the atmospheres of nearby exoplanets, new research suggests.
A new paper details how a team of astronomers from The Ohio State University examined upcoming telescopes’ ability to detect chemical traces of oxygen, carbon dioxide, methane and water on 10 rocky exoplanets. These elements are biosignatures also found in Earth’s atmosphere that can provide key scientific evidence of life.
The study found that for a pair of these nearby worlds, Proxima Centauri b and GJ 887 b, these telescopes are highly adept at detecting the presence of potential biosignatures. Of the two, findings show that only for Proxima Centauri b would the machines be able to detect carbon dioxide if it were present. Though no exoplanet has been found to precisely twin Earth’s early conditions for life, this work suggests that if examined in greater detail, such unique Super Earths — planets more massive than Earth but smaller than Neptune — could make a suitable target for future research missions.
To further the search for habitable planets, Huihao Zhang, lead author of the study and a senior in astronomy at Ohio State, and his colleagues also sought to determine the effectiveness of specialized imaging instruments like the James Webb Space Telescope (JWST) and other Extremely Large Telescopes (ELTs) such as the European Extremely Large Telescope, the Thirty-Meter-Telescope and the Giant Magellan Telescope at directly imaging exoplanets.
“Not every planet is suitable for direct imaging, but that’s why simulations give us a rough idea of what the ELTs would have delivered and the promises they’re meant to hold when they are built,” said Zhang.
The direct method of imaging exoplanets involves using a coronagraph or starshade to block a host star’s light, allowing for scientists to capture a faint image of the new world in orbit. But because locating them in this way can be difficult and time-consuming, the researchers aimed to see how well the ELT telescopes might handle the challenge. To do this, they tested each telescope’s instruments’ abilities to differentiate universal background noise from the planetary noise they aimed to capture while detecting biosignatures; called the signal-to-noise ratio, the higher it is, the easier a planet’s wavelength is able to be detected and analyzed.
Results showed that the direct imaging mode of one of the European ELT’s instruments, called the Mid-infrared ELT Imager and Spectrograph, performed better for three planets (GJ 887 b, Proxima b and Wolf 1061 c) in discerning the presence of methane, carbon dioxide and water, while its High Angular Resolution Monolithic Optical and Near-infrared Integral field spectrograph instrument could detect methane, carbon dioxide, oxygen and water, but needed a great deal more exposure time.
Additionally, since these conclusions were about instruments that will have to peer through the chemical fog of Earth’s atmosphere to progress the search for cosmic life, they were compared to JWST’s current outer space capabilities, said Zhang.
“It’s hard to say whether space telescopes are better than ground-based telescopes, because they’re different,” he said. “They have different environments, different locations, and their observations have different influences.”
In this case, findings revealed that while GJ 887 b is one of the most suitable targets for ELT direct imaging as its location and size result in an especially high signal-to-noise ratio, for some transiting planets, such as the TRAPPIST-1 system, JWST’s techniques for studying planetary atmospheres are more suitable for detecting them than direct imaging from the ELTs on Earth. But because the study took on a more conservative assumption with the data, Zhang said, the true effectiveness of future astronomical tools could still surprise scientists. And subtle contrasts in performance aside, these powerful technologies serve to widen our understanding of the universe and are meant to complement each other, said Ji Wang, co-author of the study and an assistant professor in astronomy at Ohio State. It’s why studies like this one, that assess the limitations of those technologies, is necessary, he said.
“The importance of simulation, especially for missions that cost billions of dollars, cannot be stressed enough,” said Wang. “Not only do people have to build the hardware, they also try really hard to simulate the performance and be prepared to achieve those glorious results.”
In all likelihood, as the ELTs won’t be completed until the tail end of the decade, researchers’ next steps will settle around simulating how well future ELT instruments will take to investigating the intricacies of our own planet’s rampant proofs of life.
“We want to see to what extent we can study our atmosphere to exquisite detail and how much information we can extract from it,” said Wang. “Because if we cannot answer habitability questions with Earth’s atmosphere, then there’s no way we can start to answer these questions around other planets.”
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