ST/ Simulations provide clue to missing planets mystery

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Paradigm

31 min readNov 17, 2021

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Space biweekly vol.39, 3d November — 17th November

TL;DR

New supercomputer simulations show that after creating a ring, a planet can move away and leave the ring behind. Not only does this bolster the planet theory for ring formation, the simulations show that a migrating planet can produce a variety of patterns matching those actually observed in disks.
After decades of uncertainty, researchers have confirmed the existence of lunar carbon dioxide cold traps that could potentially contain solid carbon dioxide. The discovery will likely have a major influence in shaping future lunar missions and could impact the feasibility of a sustained robot or human presence on the moon.
A near-Earth asteroid named Kamo`oalewa could be a fragment of our moon, according to a new paper.
A new method has allowed scientists to quickly detect a transiting planet with two suns.
Researchers have pinpointed the likely origin of a group of meteorites ejected from Mars, using a machine learning algorithm that analyses high-resolution planetary images.
Astronomers have discovered a small black hole outside the Milky Way by looking at how it influences the motion of a star in its close vicinity. This is the first time this detection method has been used to reveal the presence of a black hole outside of our galaxy. The method could be key to unveiling hidden black holes in the Milky Way and nearby galaxies, and to help shed light on how these mysterious objects form and evolve.
A husband-and-wife team of astronomers joined forces for the first time in their scientific careers during the pandemic to develop a new method to look back in time and change the way we understand the history of galaxies.
Strange ‘eggshell planets’ are among the rich variety of exoplanets possible, according to a study. These rocky worlds have an ultra-thin outer brittle layer and little to no topography. Such worlds are unlikely to have plate tectonics, raising questions as to their habitability. Planetary geologists have said at least three such worlds found during previous astronomical surveys may already be known.
An enormous jet of particles emitted by the giant galaxy M87 can be observed astronomically in various wavelengths. Scientists have developed a theoretical model of the morphology of this jet using complex supercomputer calculations. The images from these calculations provide an unprecedented match with astronomical observations and confirm Einstein’s theory of general relativity.
How are chemical elements produced in our Universe? Where do heavy elements like gold and uranium come from? Using computer simulations, a research team shows that the synthesis of heavy elements is typical for certain black holes with orbiting matter accumulations, so-called accretion disks. The predicted abundance of the formed elements provides insight into which heavy elements need to be studied in future laboratories to unravel the origin of heavy elements.
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Space industry in numbers

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

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

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

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Latest research

Dust Rings as a Footprint of Planet Formation in a Protoplanetary Disk

by Kazuhiro D. Kanagawa, Takayuki Muto, Hidekazu Tanaka in The Astrophysical Journal

Forming planets are one possible explanation for the rings and gaps observed in disks of gas and dust around young stars. But this theory has trouble explaining why it is rare to find planets associated with rings. New supercomputer simulations show that after creating a ring, a planet can move away and leave the ring behind. Not only does this bolster the planet theory for ring formation, the simulations show that a migrating planet can produce a variety of patterns matching those actually observed in disks.

Young stars are encircled by protoplanetary disks of gas and dust. One of the world’s most powerful radio telescope arrays, ALMA (Atacama Large Millimeter/submillimeter Array), has observed a variety of patterns of denser and less dense rings and gaps in these protoplanetary disks. Gravitational effects from planets forming in the disk are one theory to explain these structures, but follow-up observations looking for planets near the rings have largely been unsuccessful.

Time variation of dust surface density distribution in the case ofMp/M = 10−4, H0 = 0.05, and = 3×10−4. The outer dashed circle indicates the initial orbital radius of the planet at R0, and the inner dotted circle denotes the orbital radius of the planet at the particular time of each panel. In this case, tb,form = 60 t0, tb,max = 210 t0, tb,leak = 570 t0, and tb,end = 1500 t0. The cross in each panel indicates the location of the planet.

In the new research a team from Ibaraki University, Kogakuin University, and Tohoku University in Japan used the world’s most powerful supercomputer dedicated to astronomy, ATERUI II at the National Astronomical Observatory of Japan, to simulate the case of a planet moving away from its initial formation site.

Their results showed that in a low viscosity disk, a ring formed at the initial location of a planet doesn’t move as the planet migrates inwards.

Time variation of planet orbital radius in the case shown in Figure 1. Thin dashed and dotted lines indicate the lines with the migration velocity of −5 × 10−4R0/t0 (equivalent to R0/type I, type I given by Equation 5) and −1.7×10−4R0/t0 (2R0/type II, type II given by Equation 6), respectively.

The team identified three distinct phases. In Phase I, the initial ring remains intact as the planet moves inwards. In Phase II, the initial ring begins to deform and a second ring starts forming at the new location of the planet. In Phase III, the initial ring disappears and only the latter ring remains.

Schematic picture of the morphology of the dust rings and definition of evolutionary phases. As stated in the text, when the migration timescale of the planet is much shorter than dust drift timescale and deformation time of the initial (outer) ring, Phase II and III are not realized.

These results help explain why planets are rarely observed near the outer rings, and the three phases identified in the simulations match well with the patterns observed in actual rings. Higher resolution observations from next-generation telescopes, which will be better able to search for planets close to the central star, will help determine how well these simulations match reality.

Carbon Dioxide Cold Traps on the Moon

by Norbert Schorghofer, Jean‐Pierre Williams, Jose Martinez‐Camacho, David A. Paige, Matthew A. Siegler in Geophysical Research Letters

After decades of uncertainty, researchers have confirmed the existence of lunar carbon dioxide cold traps that could potentially contain solid carbon dioxide. The discovery will likely have a major influence in shaping future lunar missions and could impact the feasibility of a sustained robot or human presence on the moon.

In the permanently shadowed regions at the poles of our moon, temperatures dip below those in the coldest areas of Pluto, allowing for carbon dioxide cold traps. In these cold traps, carbon dioxide molecules could freeze and remain in solid form even during peak temperatures in the lunar summer.

Temperature time series for the spatial pixel that includes the LCROSS impact location in Cabeus Crater. (a) Temperature data are divided into six seasonal bins (based on ecliptic longitude, Ls

Future human or robot explorers could use the solid carbon dioxide in these cold traps to produce fuel or materials for longer lunar stays. The carbon dioxide and other potential volatile organics could also help scientists better understand the origin of water and other elements on the moon.

Although cold traps have been predicted by planetary scientists for years, this new study is the first to firmly establish and map the presence of carbon dioxide cold traps. To find the coldest spots on the moon’s surface, researchers analyzed 11 years of temperature data from the Diviner Lunar Radiometer Experiment, an instrument flying aboard NASA’s Lunar Reconnaissance Orbiter.

The new research, which publishes high-impact, short-format reports with immediate implications spanning all Earth and space sciences, shows that these cold traps include several pockets concentrated around the lunar southern pole. The total area of these carbon dioxide traps totals 204 square kilometers, with the largest area in the Amundsen Crater hosting 82 square kilometers of traps. In these areas, temperatures continually remain below 60 degrees Kelvin (about minus 352 degrees Fahrenheit.)

The existence of carbon dioxide cold traps does not guarantee the existence of solid carbon dioxide on the moon, but this verification does make it highly likely that future missions could find carbon dioxide ice there, according to the researchers.

Map of CO2 cold traps. Long-term average of the potential sublimation rate, E, of CO2 in the south polar region of the Moon poleward of 80°S. Areas where meant(E) <100 kg m−2Gyr−1 are colored. Black contours show the boundaries of H2

“I think when I started this, the question was, ‘Can we confidently say there are carbon dioxide cold traps on the moon or not?’” said Norbert Schörghofer, a planetary scientist at the Planetary Science Institute and lead author on the study. “My surprise was that they’re actually, definitely there. It could have been that we can’t establish their existence, [they might have been] one pixel on a map… so I think the surprise was that we really found contiguous regions which are cold enough, beyond doubt.”

The existence of carbon dioxide traps on the moon will likely have implications for the planning of future lunar exploration and international policy regarding the resource.

If there is indeed solid carbon dioxide in these cold traps, it could potentially be used in a variety of ways. Future space explorers could use the resource in the production of steel as well as rocket fuel and biomaterials, which would both be essential for sustained robot or human presence on the moon. This potential has already attracted interest from governments and private companies.

Sublimation rate of water ice and supervolatiles. The rates are calculated from extrapolated vapor pressures (Text S1 in Supporting Information S1). No measurements are available for H2

Scientists could also study lunar carbon to understand how organic compounds form and what kind of molecules can be naturally produced in these harsh environments.

The carbon dioxide cold traps could also help scientists answer long-standing questions about the origins of water and other volatiles in the Earth-moon system, according to Paul Hayne, a planetary scientist at the University of Colorado, Boulder who was not involved in the study.

Carbon dioxide could be a tracer for the sources of water and other volatiles on the lunar surface, helping scientists to understand how they arrived on the moon and on Earth.

“These should be high-priority sites to target for future landed missions,” Hayne said. “This sort of pinpoints where you might go on the lunar surface to answer some of these big questions about volatiles on the moon and their delivery from elsewhere in the solar system.”

Neutrino absorption and other physics dependencies in neutrino-cooled black hole accretion disks

by O Just, S Goriely, H-Th Janka, S Nagataki, A Bauswein in Monthly Notices of the Royal Astronomical Society

How are chemical elements produced in our Universe? Where do heavy elements like gold and uranium come from? Using computer simulations, a research team from the GSI Helmholtzzentrum für Schwerionenforschung in Darmstadt, together with colleagues from Belgium and Japan, shows that the synthesis of heavy elements is typical for certain black holes with orbiting matter accumulations, so-called accretion disks. The predicted abundance of the formed elements provides insight into which heavy elements need to be studied in future laboratories — such as the Facility for Antiproton and Ion Research (FAIR), which is currently under construction — to unravel the origin of heavy elements.

All heavy elements on Earth today were formed under extreme conditions in astrophysical environments: inside stars, in stellar explosions, and during the collision of neutron stars. Researchers are intrigued with the question in which of these astrophysical events the appropriate conditions for the formation of the heaviest elements, such as gold or uranium, exist. The spectacular first observation of gravitational waves and electromagnetic radiation originating from a neutron star merger in 2017 suggested that many heavy elements can be produced and released in these cosmic collisions. However, the question remains open as to when and why the material is ejected and whether there may be other scenarios in which heavy elements can be produced.

Snapshots of model m01M3A8 (top row) and the corresponding model without neutrino absorption, m01M3A8-no𝜈 (bottom row).

Promising candidates for heavy element production are black holes orbited by an accretion disk of dense and hot matter. Such a system is formed both after the merger of two massive neutron stars and during a so-called collapsar, the collapse and subsequent explosion of a rotating star. The internal composition of such accretion disks has so far not been well understood, particularly with respect to the conditions under which an excess of neutrons forms. A high number of neutrons is a basic requirement for the synthesis of heavy elements, as it enables the rapid neutron-capture process or r-process. Nearly massless neutrinos play a key role in this process, as they enable conversion between protons and neutrons.

“In our study, we systematically investigated for the first time the conversion rates of neutrons and protons for a large number of disk configurations by means of elaborate computer simulations, and we found that the disks are very rich in neutrons as long as certain conditions are met,” explains Dr. Oliver Just from the Relativistic Astrophysics group of GSI’s research division Theory. “The decisive factor is the total mass of the disk. The more massive the disk, the more often neutrons are formed from protons through capture of electrons under emission of neutrinos, and are available for the synthesis of heavy elements by means of the r-process. However, if the mass of the disk is too high, the inverse reaction plays an increased role so that more neutrinos are recaptured by neutrons before they leave the disk. These neutrons are then converted back to protons, which hinders the r-process.”

As the study shows, the optimal disk mass for prolific production of heavy elements is about 0.01 to 0.1 solar masses. The result provides strong evidence that neutron star mergers producing accretion disks with these exact masses could be the point of origin for a large fraction of the heavy elements. However, whether and how frequently such accretion disks occur in collapsar systems is currently unclear.

Mass-weighted averages of the electron fraction.

In addition to the possible processes of mass ejection, the research group led by Dr. Andreas Bauswein is also investigating the light signals generated by the ejected matter, which will be used to infer the mass and composition of the ejected matter in future observations of colliding neutron stars. An important building block for correctly reading these light signals is accurate knowledge of the masses and other properties of the newly formed elements.

“These data are currently insufficient. But with the next generation of accelerators, such as FAIR, it will be possible to measure them with unprecedented accuracy in the future. The well-coordinated interplay of theoretical models, experiments, and astronomical observations will enable us researchers in the coming years to test neutron star mergers as the origin of the r-process elements,” predicts Bauswein.

Lunar-like silicate material forms the Earth quasi-satellite (469219) 2016 HO3 Kamoʻoalewa

by Benjamin N. L. Sharkey, Vishnu Reddy, Renu Malhotra, Audrey Thirouin, Olga Kuhn, Albert Conrad, Barry Rothberg, Juan A. Sanchez, David Thompson, Christian Veillet in Communications Earth & Environment

A near-Earth asteroid named Kamo`oalewa could be a fragment of our moon, according to a new paper by a team of astronomers led by the University of Arizona.

Kamo`oalewa is a quasi-satellite — a subcategory of near-Earth asteroids that orbit the sun but remain relatively close to Earth. Little is known about these objects because they are faint and difficult to observe. Kamo`oalewa was discovered by the PanSTARRS telescope in Hawaii in 2016, and the name — found in a Hawaiian creation chant — alludes to an offspring that travels on its own. The asteroid is roughly the size of a Ferris wheel — between 150 and 190 feet in diameter — and gets as close as about 9 million miles from Earth.

**Kamoʻoalewa lightcurve and Rotational Properties.**

Due to its orbit, Kamo`oalewa can only be observed from Earth for a few weeks every April. Its relatively small size means that it can only be seen with one of the largest telescopes on Earth. Using the UArizona-managed Large Binocular Telescope on Mount Graham in southern Arizona, a team of astronomers led by planetary sciences graduate student Ben Sharkey found that Kamo`oalewa’s pattern of reflected light, called a spectrum, matches lunar rocks from NASA’s Apollo missions, suggesting it originated from the moon.

The team can’t yet be sure how it may have broken loose. The reason, in part, is because there are no other known asteroids with lunar origins.

“I looked through every near-Earth asteroid spectrum we had access to, and nothing matched,” said Sharkey, the paper’s lead author.

The debate over Kamo`oalewa’s origins between Sharkey and his adviser, UArizona associate professor Vishnu Reddy, led to another three years of hunting for a plausible explanation.

**Comparison of Kamoʻoalewa’s Spectral Slope with Typical NEAs.**

“We doubted ourselves to death,” said Reddy, a co-author who started the project in 2016. After missing the chance to observe it in April 2020 due to a COVID-19 shutdown of the telescope, the team found the final piece of the puzzle in 2021.

“This spring, we got much needed follow-up observations and went, ‘Wow it is real,’” Sharkey said. “It’s easier to explain with the moon than other ideas.”

Kamo`oalewa’s orbit is another clue to its lunar origins. Its orbit is similar to the Earth’s, but with the slightest tilt. Its orbit is also not typical of near-Earth asteroids, according to study co-author Renu Malhotra, a UArizona planetary sciences professor who led the orbit analysis portion of the study.

“It is very unlikely that a garden-variety near-Earth asteroid would spontaneously move into a quasi-satellite orbit like Kamo`oalewa’s,” she said. “It will not remain in this particular orbit for very long, only about 300 years in the future, and we estimate that it arrived in this orbit about 500 years ago,” Malhotra said. Her lab is working on a paper to further investigate the asteroid’s origins.

**Data Processing Validation with NASA Infrared Telescope Facility.**

Kamo`oalewa is about 4 million times fainter than the faintest star the human eye can see in a dark sky.

“These challenging observations were enabled by the immense light gathering power, of the twin 8.4-meter telescopes of the Large Binocular Telescope,” said study co-author Al Conrad, a staff scientist with the telescope.

The Star Formation History of a Post-starburst Galaxy Determined from Its Cluster Population

by Rupali Chandar, Angus Mok, K. Decker French, Adam Smercina, John-David T. Smith in The Astrophysical Journal

A husband-and-wife team of astronomers at The University of Toledo joined forces for the first time in their scientific careers during the pandemic to develop a new method to look back in time and change the way we understand the history of galaxies.

Until now forging parallel but separate careers while juggling home life and carpooling to cross country meets, Dr. Rupali Chandar, professor of astronomy, and Dr. J.D. Smith, director of the UToledo Ritter Astrophysical Research Center and professor of astronomy, merged their areas of expertise.

Post-starburst galaxy S12 and its companion to the northeast, in an HST UBR composite image (asinh-scaled).

Working along with UToledo alumnus Dr. Adam Smercina who graduated with a bachelor’s degree in physics in 2015 and is currently a postdoctoral researcher at the University of Washington, they used NASA’s Hubble Space Telescope to focus on a post-starburst galaxy nearly 500 million light years away called S12 that looks like a jellyfish with a host of stars streaming out of the galaxy on one side.

Smercina, the “glue” that brought Smith and Chandar together on this research, worked with Smith as an undergraduate student starting in 2012 on the dust and gas in post-starburst galaxies.

While spiral galaxies like our Milky Way have continued to form stars at a fairly steady rate, post-starburst galaxies experienced an intense burst of star formation sometime in the last half billion years, shutting down their star formation.

A zoomed-in, UBR color image of S12 from HST observations.

The resulting breakthrough research outlines their new method to establish the star formation history of a post-starburst galaxy using its cluster population. The approach uses the age and mass estimates of stellar clusters to determine the strength and speed of the starburst that stopped more stars from forming in the galaxy. Using this method, the astronomers discovered that S12 experienced two periods of starburst before it stopped forming stars, not one.

“Post-starbursts represent a phase of galaxy evolution that is pretty rare today,” Smith said. “We think that nearly half of all galaxies went through this phase at some point in their lives. So far, their star-forming histories have been determined almost exclusively from detailed modeling of their composite starlight.”

Smith has studied post-starburst galaxies for more than a decade, and Chandar works on the stellar clusters in galaxies that are typically about three or four times closer than those in Smith’s data.

“Clusters are like fossils — they can be age-dated and give us clues to the past history of galaxies,” Chandar said. “Clusters can only be detected in these galaxies with the clear eyed-view of the Hubble Space Telescope. No clusters can be detected in even the highest quality images taken with telescopes on the ground.”

Smith has led several large multi-wavelength projects to better understand the evolutionary history of post-starburst galaxies. He discovered, for example, that the raw fuel for star formation — gas and dust — is still present in surprising quantities in some of these systems including S12, even though no stars are currently being formed.

“While studying the light from these galaxies at multiple wavelengths has helped establish the time that the burst happened, we hadn’t been able to determine how strong and how long the burst that shutoff star formation actually was,” Smith said. “And that’s important to know to better understand how these galaxies evolve.”

The astronomers used well-studied cluster masses and star formation rates in eight nearby galaxies to develop the new method, which could be applied to determine the recent star formation histories for a number of post-starburst systems.

The locations of clusters in the 3 age intervals of interest in S12.

The researchers applied their different approach to S-12, which is short for SDSS 623–52051–207, since it was discovered and catalogued in the Sloan Digitized Sky Survey (SDSS).

“It must have had one of the highest rates of star formation of any galaxy we have ever studied,” Chandar said. “S12 is the most distant galaxy I’ve ever worked on.”

The study indicates star formation in S12 shut off 70 million years ago after a short but intense burst formed some of the most massive clusters known, with masses several times higher than similar-age counterparts forming in actively merging galaxies. The method also revealed an earlier burst of star formation that the previous method of composite starlight modeling could not detect.

“These results suggest that S12’s unusual history may be even more complicated than expected, with multiple major events compounding to fully shut off star formation,” Smith said.

A black hole detected in the young massive LMC cluster NGC 1850

by S Saracino, S Kamann, M G Guarcello, C Usher, N Bastian, I Cabrera-Ziri, M Gieles, S Dreizler, G S Da Costa, T-O Husser, V Hénault-Brunet in Monthly Notices of the Royal Astronomical Society

Using the European Southern Observatory’s Very Large Telescope (ESO’s VLT), astronomers have discovered a small black hole outside the Milky Way by looking at how it influences the motion of a star in its close vicinity. This is the first time this detection method has been used to reveal the presence of a black hole outside of our galaxy. The method could be key to unveiling hidden black holes in the Milky Way and nearby galaxies, and to help shed light on how these mysterious objects form and evolve.

The newly found black hole was spotted lurking in NGC 1850, a cluster of thousands of stars roughly 160,000 light-years away in the Large Magellanic Cloud, a neighbour galaxy of the Milky Way.

a) The central pointing of NGC 1850, as seen by MUSE. Green circles identify the position of NGC 1850 as well as the younger cluster NGC 1850B. The red cross indicates the target star. An inset of the region in the blue square is displayed in panel b). The image is taken from an archival HST/WFC3 image in the F814W band. The position of the target star is highlighted by red arrows. (c) Optical CMD of NGC 1850 from the archival HST data.

“Similar to Sherlock Holmes tracking down a criminal gang from their missteps, we are looking at every single star in this cluster with a magnifying glass in one hand trying to find some evidence for the presence of black holes but without seeing them directly,” says Sara Saracino from the Astrophysics Research Institute of Liverpool John Moores University in the UK, who led the research. “The result shown here represents just one of the wanted criminals, but when you have found one, you are well on your way to discovering many others, in different clusters.”

This first “criminal” tracked down by the team turned out to be roughly 11 times as massive as our Sun. The smoking gun that put the astronomers on the trail of this black hole was its gravitational influence on the five-solar-mass star orbiting it.

Astronomers have previously spotted such small, “stellar-mass” black holes in other galaxies by picking up the X-ray glow emitted as they swallow matter, or from the gravitational waves generated as black holes collide with one another or with neutron stars. However, most stellar-mass black holes don’t give away their presence through X-rays or gravitational waves.

“The vast majority can only be unveiled dynamically,” says Stefan Dreizler, a team member based at the University of Göttingen in Germany. “When they form a system with a star, they will affect its motion in a subtle but detectable way, so we can find them with sophisticated instruments.”

Merged RGB Chandra/ACIS-S images of NGC 1850 analyzed in this work, with events in the hard bands in red, medium band in green, and soft band in blue. The left panel shows the whole eld, while the right panel is centered on the position of the candidate black hole and the bright SNR N103B.

This dynamical method used by Saracino and her team could allow astronomers to find many more black holes and help unlock their mysteries. “Every single detection we make will be important for our future understanding of stellar clusters and the black holes in them,” says study co-author Mark Gieles from the University of Barcelona, Spain.

The detection in NGC 1850 marks the first time a black hole has been found in a young cluster of stars (the cluster is only around 100 million years old, a blink of an eye on astronomical scales). Using their dynamical method in similar star clusters could unveil even more young black holes and shed new light on how they evolve. By comparing them with larger, more mature black holes in older clusters, astronomers would be able to understand how these objects grow by feeding on stars or merging with other black holes. Furthermore, charting the demographics of black holes in star clusters improves our understanding of the origin of gravitational wave sources.

To carry out their search, the team used data collected over two years with the Multi Unit Spectroscopic Explorer (MUSE) mounted at ESO’s VLT, located in the Chilean Atacama Desert. “MUSE allowed us to observe very crowded areas, like the innermost regions of stellar clusters, analysing the light of every single star in the vicinity. The net result is information about thousands of stars in one shot, at least 10 times more than with any other instrument,” says co-author Sebastian Kamann, a long-time MUSE expert based at Liverpool’s Astrophysics Research Institute. This allowed the team to spot the odd star out whose peculiar motion signalled the presence of the black hole. Data from the University of Warsaw’s Optical Gravitational Lensing Experiment and from the NASA/ESA Hubble Space Telescope enabled them to measure the mass of the black hole and confirm their findings.

ESO’s Extremely Large Telescope in Chile, set to start operating later this decade, will allow astronomers to find even more hidden black holes. “The ELT will definitely revolutionise this field,” says Saracino. “It will allow us to observe stars considerably fainter in the same field of view, as well as to look for black holes in globular clusters located at much greater distances.”

TIC 172900988: A Transiting Circumbinary Planet Detected in One Sector of TESS Data

by Veselin B. Kostov, Brian P. Powell, Jerome A. Orosz, William F. Welsh, et al. in The Astronomical Journal

A new technique developed in part by University of Hawaii astronomer Nader Haghighipour has allowed scientists to quickly detect a transiting planet with two suns.

Termed circumbinary planets, these objects orbit around a pair of stars. For years, these planets were merely the subject of science fiction, like Tatooine in Star Wars. However, thanks to NASA’s successful planet-hunting Kepler and Transiting Exoplanet Survey Satellite (TESS) missions, a team of astronomers, including Haghighipour, have found 14 such bodies so far.

Left: 4:30 4:30 DSS red image of the target (highlighted with yellow cross-hair); Right: 4:30 4:30 Skyview image superimposed on the TESS pixels of the target for Sector 21, showing all nearby resolved Gaia sources down to G = 21 mag.

Kepler and TESS detect planets via the transit method, where astronomers measure the tiny dimming of a star as a planet passes in front of its host star, blocking some of the starlight. Usually, astronomers need to see at least three of these transits to pin down the planet’s orbit. This becomes challenging when there are two host stars.

“Detecting circumbinary planets is much more complicated than finding planets orbiting single stars. When a planet orbits a double-star system, transits of the same star don’t occur at consistent intervals,” explained Haghighipour. “The planet might transit one star, and then transit the other, before transiting the first star again, and so on.”

Adding to the challenge, the orbital periods of circumbinary planets are always much longer than the orbital period of the binary star. That means, in order to observe three transits, scientists need to observe the binary for a long time. While that was not a problem with the Kepler space telescope (this telescope observed only one region of the sky for 3.5 years), it makes it challenging to use the TESS telescope to detect circumbinary planets, because TESS observes one portion (or sector) of the sky for only 27 days before pointing someplace else, making it impossible to observe three transits of a planet with TESS.

Archival and follow-up phototometric observations of TIC 1729 highlighting the baseline covered from the available data.

In 2020, Haghighipour and his team found a way around this limitation. In an article published in The Astronomical Journal, they described a novel technique that would enable them to detect circumbinary planets using TESS, as long as the planet transited both of its host stars within the 27-day observing window.

Now, that same team of astronomers has actually found the first such circumbinary planet in TESS data, demonstrating that their technique works. The target binary is known by its catalog designation, TIC 172900988, and was observed in a single sector by TESS, where its lightcurve showed signs of two transits, one across each star, separated by just five days — during the same conjunction.

“This planet’s orbit takes almost 200 days — with the traditional transit method, we would have needed to wait over a year to detect two additional transits. Our new technique reduced that time to just five days, showing that despite its short window of observation, TESS can be used to detect circumbinary planets. The new planet is the proof of the validity, applicability and success of our invented technique,” said Haghighipour, founder of the TESS Circumbinary Planet Working Group. “This discovery demonstrates that our new technique works and will be able to find many more planets.”

The Effects of Planetary and Stellar Parameters on Brittle Lithospheric Thickness

by Paul K. Byrne, Bradford J. Foley, Marie E. S. Violay, Michael J. Heap, Sami Mikhail in Journal of Geophysical Research: Planets

Strange ‘eggshell planets’ are among the rich variety of exoplanets possible, according to a study from Washington University in St. Louis. These rocky worlds have an ultra-thin outer brittle layer and little to no topography. Such worlds are unlikely to have plate tectonics, raising questions as to their habitability.

Only a small subset of extrasolar planets are likely eggshell planets. Planetary geologist Paul Byrne, first author of the new modeling study, said at least three such worlds found during previous astronomical surveys may already be known. Scientists could use planned and future space telescopes to examine these exoplanets in greater detail and confirm their geological characteristics.

Calculated brittle–ductile transition depths as a function of surface gravitational acceleration, g (a), plate age, t, (b), surface temperature, Ts ©, and mantle interior temperature, Tm (d).

“Understanding whether you’ve got the possibility of plate tectonics is a really important thing to know about a world, because plate tectonics may be required for a large rocky planet to be habitable,” said Byrne, associate professor in the Department of Earth and Planetary Sciences in Arts & Sciences and a faculty fellow of the university’s McDonnell Center for the Space Sciences. “It’s therefore especially important when we’re talking about looking for Earth-like worlds around other stars and when we’re characterizing planetary habitability generally.”
“What we’ve laid out here is essentially a how-to guide, or handy manual,” he said. “If you have a planet of a given size, at a given distance from its star and of a given mass, then with our results you can make some estimates for a variety of other features — including whether it may have plate tectonics.”

To date, exoplanets have largely been the domain of astronomers, because space scientists rely on astronomical techniques and instruments to detect exoplanets. More than 4,000 exoplanets have been discovered and are considered “confirmed.” Byrne’s study offers new and concrete ways that other scientists could identify eggshell planets, as well as other types of exoplanets that could be interesting because of their particular combinations of size, age and distance to their host star.

“We have imaged a few exoplanets, but they are splotches of light orbiting a star. We have no technical ability to actually see the surface of exoplanets yet,” Byrne said. “This paper is one of a small but growing number of studies taking a geological or geophysical perspective to try and understand the worlds that we cannot directly measure right now.”

Planets have certain qualities that are inherent to the planets themselves, like their size, interior temperature and the materials that they are made of. Other properties are more of a function of the planet’s environment, like how far it is from the sun. The planets that humans know best are those in our own solar system — but these truths are not necessarily universal for planets that orbit other stars.

“We know from published work that there are exoplanets that experience conditions in a more extreme way than what we see in our solar system,” Byrne said. “They might be closer to their star, or they might be much larger, or have hotter surfaces, than the planets we see in our own system.”

Byrne and his collaborators wanted to see which planetary and stellar parameters play the most important role in determining the thickness of a planet’s outer brittle layer, which is known as the lithosphere. This thickness helps determine whether, for example, a planet can support high topography such as mountains, or has the right balance between rigidity and flexibility for one part of the surface to dive down, or subduct, beneath another — the hallmark of plate tectonics. It is this process that helps Earth regulate its temperature over geological timescales, and the reason why plate tectonics is thought to be an important component of planetary habitability. For their modeling effort, the scientists chose a generic rocky world as a starting point.

“And then we spun the dials,” Byrne said. “We literally ran thousands of models.”

Calculated BDT depths as a function of surface temperature, Ts, with model colored by surface gravitational acceleration, g. In all cases, p = 0.5, q = 2, and there is no pore pressure present. Here, strain rate is as follows: 10–13 s–1 (a), 10–14 s–1 (b), 10–15 s–1 (c), and 10–16 s–1 (d).

They discovered that surface temperature is the primary control on the thickness of brittle exoplanet lithospheres, although planetary mass, distance to its star and even age all play a role. The new models predict that worlds that are small, old or far from their star likely have thick, rigid layers, but, in some circumstances, planets might have an outer brittle layer only a few kilometers thick — these so-called eggshell planets.

Although we are a long way from directly imaging the surfaces of these eggshell planets, they might resemble the lowlands on Venus, Byrne noted. Those lowlands contain vast expanses of lavas but have little high-standing terrain, because the lithosphere there is thin as a result of searing surface temperatures.

“Our overall goal is more than just understanding the vagaries of exoplanets,” Byrne said. “Ultimately we want to help contribute to identifying the properties that make a world habitable. And not just temporarily, but habitable for a long time, because we think life probably needs a while to get going and become sustainable.”

The fundamental question behind this research is, of course, are we alone?

“That is the big reach,” Byrne said. “Ultimately most of this work is tied into this final destination, which is ‘how unique, or not, is Earth?’ One of the many things we are going to need to know is what kinds of properties influence a world like Earth. And this study helps address some of that question by showing the kinds of ways these parameters interact, what other outcomes might be possible and which worlds we should prioritize for study with new-generation telescopes.”

State-of-the-art energetic and morphological modelling of the launching site of the M87 jet

by Alejandro Cruz-Osorio, Christian M. Fromm, Yosuke Mizuno, Antonios Nathanail, Ziri Younsi, Oliver Porth, Jordy Davelaar, Heino Falcke, Michael Kramer, Luciano Rezzolla in Nature Astronomy

The galaxy Messier 87 (M87) is located 55 million light years away from Earth in the Virgo constellation. It is a giant galaxy with 12,000 globular clusters, making the Milky Way’s 200 globular clusters appear modest in comparison. A black hole of six and a half billion sun masses is harboured at the centre of M87. It is the first black hole for which an image exists, created in 2019 by the international research collaboration Event Horizon Telescope.

This black hole (M87*) shoots a jet of plasma at near the speed of light, a so-called relativistic jet, on a scale of 6,000 light years. The tremendous energy needed to power this jet probably originates from the gravitational pull of the black hole, but how a jet like this comes about and what keeps it stable across the enormous distance is not yet fully understood.

**Large-scale morphology of the jet from GRMHD simulations of a Kerr BH with spin a⋆ = 0.9375 (the BH spin is aligned with the z axis).**

The black hole M87* attracts matter that rotates in a disc in ever smaller orbits until it is swallowed by the black hole. The jet is launched from the centre of the accretion disc surrounding M87, and theoretical physicists at Goethe University, together with scientists from Europe, USA and China, have now modelled this region in great detail.

They used highly sophisticated three-dimensional supercomputer simulations that use the staggering amount of a million CPU hours per simulation and had to simultaneously solve the equations of general relativity by Albert Einstein, the equations of electromagnetism by James Maxwell, and the equations of fluid dynamics by Leonhard Euler.

The result was a model in which the values calculated for the temperatures, the matter densities and the magnetic fields correspond remarkably well with what deduced from the astronomical observations. On this basis, scientists were able to track the complex motion of photons in the curved spacetime of the innermost region of the jet and translate this into radio images. They were then able to compare these computer modelled images with the observations made using numerous radio telescopes and satellites over the past three decades.

Dr Alejandro Cruz-Osorio, lead author of the study, comments: “Our theoretical model of the electromagnetic emission and of the jet morphology of M87 matches surprisingly well with the observations in the radio, optical and infrared spectra. This tells us that the supermassive black hole M87* is probably highly rotating and that the plasma is strongly magnetized in the jet, accelerating particles out to scales of thousands of light years.”
Professor Luciano Rezzolla, Institute for Theoretical Physics at Goethe University Frankfurt, remarks: “The fact that the images we calculated are so close to the astronomical observations is another important confirmation that Einstein’s theory of general relativity is the most precise and natural explanation for the existence of supermassive black holes in the centre of galaxies. While there is still room for alternative explanations, the findings of our study have made this room much smaller.”

The Tharsis mantle source of depleted shergottites revealed by 90 million impact craters

by Lagain, A., Benedix, G.K., Servis, K. et al. in Nature Communications

Curtin University researchers have pinpointed the likely origin of a group of meteorites ejected from Mars, using a machine learning algorithm that analyses high-resolution planetary images.

The new research identified meteorites that landed on Earth likely originated from Mars’ Tooting crater, located in the Tharsis region, which is the largest volcanic province in the solar system.

About 166 Martian rocks have landed on Earth over the past 20 million years, however their precise origins on Mars were unknown.

Lead researcher Dr Anthony Lagain, from Curtin University’s Space Science and Technology Centre in the School of Earth and Planetary Sciences, said the new findings would help provide the context to unravel the geological history of the Red Planet.

“In this study, we compiled a new database of 90 million impact craters using a machine learning algorithm that allowed us to determine the potential launch positions of Martian meteorites,” Dr Lagain said.
“By observing the secondary crater fields — or the small craters formed by the ejecta that was thrown out of the larger crater formed recently on the planet, we found that the Tooting crater is the most likely source of these meteorites ejected from Mars 1.1 million years ag
“For the first time, through this research, the geological context of a group of Martian meteorites is accessible, 10 years before NASA’s Mars Sample Return mission is set to send back samples collected by the Perseverance rover currently exploring the Jezero crater.”

Co-Lead Professor Gretchen Benedix, also from Curtin University’s Space Science and Technology Centre, said the algorithm that made this possible was a major step forward in how scientists can use the terabytes of planetary data available.

“We would not have been able to recognise the youngest craters on Mars without counting the tens of millions of craters smaller than one kilometre across,” Professor Benedix said.
“This finding implies that volcanic eruptions occurred in this region 300 million years ago, which is very recent at a geological time scale. It also provides new insights on the structure of the planet, beneath this volcanic province.”

**Close-up of cratering density around the two most likely crater source of the depleted shergottites.**

Dr Lagain said the research would help create a better understanding of the formation and the evolution of Mars, as well as Earth, potentially offering benefits for other industry sectors on our planet.

“Mapping craters on Mars is a first step. The algorithm we developed can be retrained to perform automated digital mapping of any celestial body. It can be applied to Earth to assist with managing agriculture, the environment and even potentially natural disasters such as fires or floods,” Dr Lagain said.

The algorithm was developed in-house by an interdisciplinary group that included members from CSIRO, the Curtin Institute for Computation and the School of Civil and Mechanical Engineering with funding from the Australian Research Council. Using the fastest supercomputer in the Southern Hemisphere, the Pawsey Supercomputing Centre, and the Curtin HIVE (Hub for Immersive Visualisation and eResearch), researchers analysed a very large volume of high-resolution planetary images through a machine learning algorithm to detect impact craters.