ST/ Ravenous black hole consumes three Earths’-worth of star every time it passes

Paradigm

Published in

Paradigm

39 min readSep 14, 2023

Space biweekly vol.84, 1st September — 14th September

TL;DR

Massive burst of X-rays detected by astronomers indicates material three times the mass of Earth burning up in a black hole. They observed a star like our own Sun being eaten away every time it orbits close. First time a Sun-like star being repeatedly disrupted by a low mass black hole has been seen, opening the possibility of a range of star and black hole combinations to be discovered.
New research has revealed the distribution of dark matter in never before seen detail, down to a scale of 30,000 light-years. The observed distribution fluctuations provide better constraints on the nature of dark matter.
A new article hints at the existence of several black holes in the Hyades cluster — the closest open cluster to our solar system — which would make them the closest black holes to Earth ever detected.
The planet HAT-P-32b is losing so much of its atmospheric helium that the trailing gas tails are among the largest structures yet known any planet outside our solar system. Three-dimensional (3D) simulations helped model the flow of the planet’s atmosphere. The scientists hope to widen their planet-observing net and survey 20 additional star systems to find more planets losing their atmosphere and learn about their evolution.
Astronomers have detected the magnetic field of a galaxy so far away that its light has taken more than 11 billion years to reach us: we see it as it was when the Universe was just 2.5 billion years old. The result provides astronomers with vital clues about how the magnetic fields of galaxies like our own Milky Way came to be.
While astrophysicists previously believed that only supernovae could generate long gamma-ray bursts (GRBs), a 2021 observation uncovered evidence that compact-object mergers also can generate the phenomenon. Now, a new simulation confirms and explains this finding. If the accretion disk around the black hole is massive, it launches a jet that lasts several seconds, matching the description of a long GRB from a merger.
Astronomers have uncovered a link between Neptune’s shifting cloud abundance and the 11-year solar cycle, in which the waxing and waning of the Sun’s entangled magnetic fields drives solar activity.
Scientists have detected and validated two of the longest-period exoplanets found by TESS to date. These long period large exoplanets orbit a K dwarf star and belong to a class of planets known as warm Jupiters, which have orbital periods of 10–200 days and are at least six times Earth’s radius. This recent discovery offers exciting research opportunities for the future of finding long-period planets that resemble those in our own solar system.
In experiments aboard the International Space Station, a surface treatment developed engineers prevented the growth of microbial biofims. These films can damage equipment and potentially cause illness.
With a remarkable observational campaign that involved 12 telescopes both on the ground and in space, including three European Southern Observatory (ESO) facilities, astronomers have uncovered the strange behavior of a pulsar, a super-fast-spinning dead star. This mysterious object is known to switch between two brightness modes almost constantly, something that until now has been an enigma. But astronomers have now found that sudden ejections of matter from the pulsar over very short periods are responsible for the peculiar switches.
And more!

Space industry in numbers

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

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

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

Space industry news

Latest research

Monthly quasi-periodic eruptions from repeated stellar disruption by a massive black hole

by P. A. Evans, C. J. Nixon, S. Campana, P. Charalampopoulos, D. A. Perley, A. A. Breeveld, K. L. Page, S. R. Oates, R. A. J. Eyles-Ferris, D. B. Malesani, L. Izzo, M. R. Goad, P. T. O’Brien, J. P. Osborne, B. Sbarufatti in Nature Astronomy

A star like our own Sun in a nearby galaxy is gradually being eaten away by a small but ravenous black hole, losing the equivalent mass of three Earths every time it passes close.

The discovery by University of Leicester astronomers provides a ‘missing link’ in our knowledge of black holes disrupting orbiting stars. It suggests a whole menagerie of stars in the process of being consumed that still lie undiscovered.

The astronomers were alerted to the star by a bright X-ray flash that seemed to come from the centre of the nearby galaxy 2MASX J02301709+2836050, around 500 million light-years away from the Milky Way. Named Swift J0230, it was spotted the moment it happened for the first time using a new tool developed by the scientists for the Neil Gehrels Swift Observatory. They rapidly scheduled further Swift observations of it, finding that instead of decaying away as expected, it would shine brightly for 7–10 days and then abruptly switch off, repeating this process roughly every 25 days.

Similar behaviour has been observed in what are termed quasi-periodic eruptions and periodic nuclear transients, where a star has material ripped away by a black hole as its orbit takes it close by, but they differ in how often they erupt, and in whether it is in X-rays or optical light that the explosion is predominant. The regularity of Swift J0230’s emissions fell between the two, suggesting that it forms the ‘missing link’ between the two types of outburst.

Location of the new transient, Swift J0230, relative to its host galaxy and an old supernova.

Using the models proposed for these two classes of event as a guide, the scientists concluded that the Swift J0230 outburst represents a star of a similar size to our own sun in an elliptical orbit around a low-mass black hole at the centre of its galaxy. As the star’s orbit takes it close to the intense gravitational pull of the black hole, material equivalent to the mass of three Earths is wrenched from the atmosphere of the star and heated up as it falls into the black hole. The intense heat, around 2 million degrees Celsius, releases a huge amount of X-rays which were first picked up by the Swift satellite.

Lead author Dr Phil Evans of the University of Leicester School of Physics and Astronomy said: “This is the first time we’ve seen a star like our Sun being repeatedly shredded and consumed by a low mass black hole. So-called ‘repeated, partial tidal disruption’ events are themselves quite a new discovery and seem to fall into two types: those that outburst every few hours, and those that outburst every year or so. This new system falls right into the gap between these, and when you run the numbers, you find the types of objects involved fall nicely into place too.”

Dr Rob Eyles-Ferris, who works with Dr Evans on the Swift satellite, recently completed his PhD at Leicester, which included the study of stars being disrupted by black holes. He explains: “In most of the systems we’ve seen in the past the star is completely destroyed. Swift J0230 is an exciting addition to the class of partially-disrupted stars as it shows us that the two classes of these objects already found are really connected, with our new system giving us the missing link.”

Optical spectrum of the host galaxy 2MASX J02301709+2836050 obtained with the NOT on day 132.

Dr Kim Page from the University of Leicester, who worked on the data analysis for the study, said: “Given that we found Swift J0230 within a few months of enabling our new transient-hunting tool, we expect that there are a lot more objects like this out there, waiting to be uncovered.”

Dr Chris Nixon is a theoretical astrophysicist who recently moved from the University of Leicester to the University of Leeds. He led the theoretical interpretation of this event. His research is funded by the UK Science and Technology Facilities Council and the Leverhulme Trust.

They estimate that the black hole is around 10,000 to 100,000 times the mass of our sun, which is quite small for the supermassive black holes usually found at the centre of galaxies. The black hole at the centre of our own galaxy is thought to be 4 million solar masses, while most are in the region of 100 million solar masses.

It is the first discovery to be made using the new transient detector for the Swift satellite, developed by the University of Leicester team and running on their computers. When an extreme event takes place, causing an X-ray burst in a region of the sky where there were previously no X-rays, astronomers call it an astronomical X-ray transient. Despite the extreme events they herald, these events are not easy to find, or at least, not quickly — and so this new tool was developed to look for new types of transients in real time.

Dr Evans adds: “This type of object was essentially undetectable until we built this new facility, and soon after it found this completely new, never-before-seen event. Swift is nearly 20 years old and it’s suddenly finding brand new events that we never knew existed. I think it shows that every single time you find a new way of looking at space, you learn something new and find there’s something out there you didn’t know about before.”
Dr Caroline Harper, Head of Space Science at the UK Space Agency, said:“This is yet another exciting discovery from the world-leading Swift mission — a low mass black hole taking ‘bites’ from a Sun-like star whenever it orbits close enough.
“The UK Space Agency has been working in partnership with NASA on this mission for many years; the UK led on the development of hardware for two of the key science instruments and we provided funding for the Swift Science Data Centre, which we continue to support. We look forward to even more insights from Swift about gamma ray bursts throughout the cosmos, and the massive events that cause them, in the future.”

ALMA Measurement of 10 kpc Scale Lensing-power Spectra toward the Lensed Quasar MG J0414+0534

by Kaiki Taro Inoue, Takeo Minezaki, Satoki Matsushita, Kouichiro Nakanishi in The Astrophysical Journal

New research has revealed the distribution of dark matter in never before seen detail, down to a scale of 30,000 light-years. The observed distribution fluctuations provide better constraints on the nature of dark matter.

Mysterious dark matter accounts for most of the matter in the Universe. Dark matter is invisible and makes itself know only through its gravitational effects. Dark matter has never been isolated in a laboratory, so researchers must rely on “natural experiments” to study it.

One type of natural experiment is a gravitational lens. Sometimes by random chance, two objects at different distances in the Universe will lie along the same line-of-sight when seen from Earth. When this happens, the spatial curvature caused by the matter around the foreground object acts like a lens, bending the path of light from the background object and making a lensed image. However, it is difficult to achieve the high resolution to detect clumps of dark matter which are less massive than galaxies in natural experiments, so the exact nature of dark matter has been poorly constrained.

Schematic picture of halos (yellow disks) and troughs (blue bars) in sight lines. The cylinder represents bundles of light rays that pass the vicinity of an Einstein ring in the lens plane.

A team of Japanese researchers led by Professor Kaiki Taro Inoue at Kindai University used ALMA (Atacama Large Millimeter/submillimeter Array) to study the gravitational lens system known as MG J0414+0534 in the direction of the constellation Taurus. In this system, the foreground object forms not one, but four images of the background object due to the gravitational force of a massive galaxy acting on the light. With the help of the bending effect and their new data analysis method, the team was able to detect fluctuations in the dark matter distribution along the line-of-sight in higher resolution than ever before, down to a scale of 30,000 light-years.

The new constraints provided by the observed distribution are consistent with models for slow moving, or “cold,” dark matter particles.

In the future the team plans to further constrain the nature of dark matter with additional observations.

Stellar-mass black holes in the Hyades star cluster?

by S Torniamenti, M Gieles, Z Penoyre, T Jerabkova, L Wang, F Anders in Monthly Notices of the Royal Astronomical Society

A new paper hints at the existence of several black holes in the Hyades cluster — the closest open cluster to our solar system — which would make them the closest black holes to Earth ever detected. The study results from a collaboration between a group of scientists led by Stefano Torniamenti, from the University of Padua (Italy), with the significant participation of with Mark Gieles, ICREA professor at the Faculty of Physics, the Institute of Cosmos Sciences of the University of Barcelona (ICCUB) and the Institute of Space Studies of Catalonia (IEEC), and Friedrich Anders (ICCUB-IEEC).

Specifically, the finding took place during a research stay of the expert Stefano Torniamenti at the ICCUB, one of the research units that make up the IEEC.

Since their discovery, black holes have been one of the most mysterious and fascinating phenomena in the Universe and have become the object of study for researchers all over the world. This is particularly true for small black holes because they have been observed during the detection of gravitational waves. Since the detection of the first gravitational waves in 2015, experts have observed many events that correspond to mergers of low-mass black hole pairs. For the published study, the team of astrophysicists used simulations that track the motion and evolution of all the stars in the Hyades — located at a distance from the Sun of about 45 parsecs or 150 light-years — to reproduce their current state.

Open clusters are loosely bound groups of hundreds of stars that share certain properties such as age and chemical characteristics. The simulation results were compared with the actual positions and velocities of the stars in the Hyades, which are now known precisely from observations made by the European Space Agency’s (ESA) Gaia satellite.

“Our simulations can only simultaneously match the mass and size of the Hyades if some black holes are present at the centre of the cluster today (or until recently),” says Stefano Torniamenti, postdoctoral researcher at the University of Padua and first author of the paper.

The observed properties of the Hyades are best reproduced by simulations with two or three black holes at present, although simulations where all the black holes have been ejected (less than 150 million years ago, roughly the last quarter of the cluster’s age) can still give a good match, because the evolution of the cluster could not erase the traces of its previous black hole population. The new results indicate that the Hyades-born black holes are still inside the cluster, or very close to the cluster. This makes them the closest black holes to the Sun, much closer than the previous candidate (namely the black hole Gaia BH1, which is 480 parsecs from the Sun).

In recent years, the breakthrough of the Gaia space telescope has made it possible for the first time to study the position and velocity of open cluster stars in detail and to identify individual stars with confidence.

“This observation helps us understand how the presence of black holes affects the evolution of star clusters and how star clusters in turn contribute to gravitational wave sources,” says Mark Gieles, a member of the UB Department of Quantum Physics and Astrophysics and host of the first author in Barcelona. “These results also give us insight into how these mysterious objects are distributed across the galaxy.”

Giant tidal tails of helium escaping the hot Jupiter HAT-P-32 b

by Zhoujian Zhang, Caroline V. Morley, Michael Gully-Santiago, et al in Science Advances

A planet about 950 light years from Earth could be the Looney Tunes’ Yosemite Sam equivalent of planets, blowing its atmospheric ‘top’ in spectacular fashion.

The planet called HAT-P-32b is losing so much of its atmospheric helium that the trailing gas tails are among the largest structures yet known of an exoplanet, a planet outside our solar system, according to observations by astronomers.

Three-dimensional (3D) simulations on the Stampede2 supercomputer of the Texas Advanced Computing Center (TACC) helped model the flow of the planet’s atmosphere, based on data from the Hobby-Eberly Telescope of The University of Texas at Austin’s McDonald Observatory. The scientists hope to widen their planet-observing net and survey 20 additional star systems to find more planets losing their atmosphere and learn about their evolution.

“We have monitored this planet and the host star with long time series spectroscopy, observations made of the star and planet over a couple of nights. And what we found is there’s a gigantic helium gas tail that is associated with the planet. The tail is large — about 53 times the planet’s radius — formed by gas that’s escaping from the planet,” said Zhoujian Zhang, a postdoctoral fellow in the Department of Astronomy & Astrophysics, University of California Santa Cruz.

Zhang is the lead author in a study on the helium tail detected from HAT-P 32b. The science team used data from the Habitable Planet Finder spectrograph, an instrument on the Hobby-Eberly telescope, which provides high spectral resolution of light in near infrared wavelengths.

The planet HAT-P-32b was discovered in 2011 using spectroscopic data from the Hungarian-made Automated Telescope Network. It’s known as a ‘hot Jupiter,’ a gas giant similar to our neighboring planet Jupiter, but with a radius twice as large. This hot Jupiter hugs closely in orbit to its host star, about three percent the distance from the Earth to the Sun. Its orbital period — what we consider a year here on Earth — is only 2.15 days, and this proximity to the star scorches it with both long and short wave radiation. The main motivation for the scientists’ interest in studying hot Jupiters is their pursuit of the mystery of the Neptunian desert, the inexplicable relative scarcity on average of intermediate-mass planets, or sub-Jupiters, with short orbital periods.

Measured helium excess in HAT-P-32 A+b planetary system.

“One of the potential explanations is that maybe the planets are losing their mass,” Zhang offered. “If we can capture planets in the process of losing their atmosphere, then we can study how fast the planet is losing their mass and what are the mechanisms that cause their atmosphere to escape from the planet. It’s good to have some examples to see like the HAT-P-32b process in action.”

The light analyzed in the study comes from the star HAT-P-32 A. It’s slightly hotter and similar in size to our own sun. The analyzed light is not just straight starlight. As the planet passes in front of the star, for just a couple of hours the starlight gets filtered the most by the planet’s gassy atmosphere. This filtering, called absorption, reveals features of the transiting planet, in this case huge outflows of helium when the spectra were analyzed.

Zhang and colleagues used a technique called transmission spectroscopy to separate the starlight into its component frequencies, like a prism separates sunlight into a rainbow spectrum. Gaps in the spectrum indicate light being absorbed by elements in the gaseous atmosphere of HAT-P-32b.

“What we see in our data is that when the planet is transiting the star, we see there’s deeper helium absorption lines. The helium absorption is stronger than what we expect from the stellar atmosphere. This excess helium absorption should be caused by the planet’s atmosphere. When the planet is transiting, its atmosphere is so huge that it blocks part of the atmosphere that absorbs the helium line, and that causes this excess absorption. That’s how we discovered the HAT-P-32b to be an interesting planet,” Zhang said.

It got more interesting as they developed 3D hydrodynamical simulations of the HAT-P-32b and host star, led by Antonija Oklopčić, Anton Pannekoek Institute for Astronomy, University of Amsterdam; and Morgan MacLeod, Institute for Theory and Computation, Harvard-Smithsonian Center for Astrophysics, Harvard University.

The models examined the interactions between the planetary outflow and stellar winds in the tidal gravitational field of the extrasolar system. The models showed columnar tails of planetary outflow both leading and trailing the planet along its orbital path with excess helium absorption even far from the transit points that matched observations. What is more, the models suggest complete loss of the atmosphere in about 4 x 10e10 Earth years.

“We made use of TACC’s Stampede2 system’s Intel Skylake nodes for our calculations,” MacLeod said. “This computation involves tracking flow as it accelerates from a slow-moving subsonic ‘atmosphere’ near the planet to a supersonic wind as it moves further away. The HAT-P-32b system was identified to have a large-scale outflow similar in size to the planet’s orbit around the star. Taken together, these requirements suggest the need for a stable, high-accuracy algorithm for solving three-dimensional gas dynamics.”

The modelers utilized the Athena++ hydrodynamic software and a custom problem setup to do their calculation on Stampede2. With it they solve the equations of gas dynamics in a rotating frame of reference that matches the planet’s orbital motion. Athena++ is a Eulerian code — the flow is discretized with volume elements — and they used nested layers of mesh refinement to capture the large-scale star-planet system along with the much smaller scale of the atmosphere near the planet’s surface.

“Using the TACC HPC systems is a joy,” MacLeod said. “A few things go into this — the first, and most important is the level of support. Whenever I have a problem, I can call the support line, get help, and get back to doing the science that I am best at. Secondly, the vast majority of my time goes into developing and validating model results, rather than running a single, full-scale calculation. The TACC systems are incredibly well set up for this reality, and it hugely speeds up the pace of development. Being able to run test calculations through the development queues or submit larger calculations of a range of sizes in the lead up to an eventual final model is crucial and effective in these environments.”

Looking ahead, the scientists hope to continue to develop sophisticated 3D models that capture effects such as atmospheric mixing of gases and even winds within the atmosphere on more distant worlds hundreds and even thousands of light years away.

Polarized thermal emission from dust in a galaxy at redshift 2.6

by Geach, J.E., Lopez-Rodriguez, E., Doherty, M.J. et al. in Nature

Using the Atacama Large Millimeter/submillimeter Array (ALMA), astronomers have detected the magnetic field of a galaxy so far away that its light has taken more than 11 billion years to reach us: we see it as it was when the Universe was just 2.5 billion years old. The result provides astronomers with vital clues about how the magnetic fields of galaxies like our own Milky Way came to be.

Lots of astronomical bodies in the Universe have magnetic fields, whether it be planets, stars or galaxies. “Many people might not be aware that our entire galaxy and other galaxies are laced with magnetic fields, spanning tens of thousands of light-years,” says James Geach, a professor of astrophysics at the University of Hertfordshire, UK, and lead author of the study.

“We actually know very little about how these fields form, despite their being quite fundamental to how galaxies evolve,” adds Enrique Lopez Rodriguez, a researcher at Stanford University, USA, who also participated in the study. It is not clear how early in the lifetime of the Universe, and how quickly, magnetic fields in galaxies form because so far astronomers have only mapped magnetic fields in galaxies close to us.

Now, using ALMA, in which the European Southern Observatory (ESO) is a partner, Geach and his team have discovered a fully formed magnetic field in a distant galaxy, similar in structure to what is observed in nearby galaxies. The field is about 1000 times weaker than the Earth’s magnetic field, but extends over more than 16,000 light-years.

The magnetic field orientation of the gravitationally lensed galaxy 9io9 at z = 2.553.

“This discovery gives us new clues as to how galactic-scale magnetic fields are formed,” explains Geach. Observing a fully developed magnetic field this early in the history of the Universe indicates that magnetic fields spanning entire galaxies can form rapidly while young galaxies are still growing.

The team believes that intense star formation in the early Universe could have played a role in accelerating the development of the fields. Moreover, these fields can in turn influence how later generations of stars will form. Co-author and ESO astronomer Rob Ivison says that the discovery opens up “a new window onto the inner workings of galaxies, because the magnetic fields are linked to the material that is forming new stars.”

To make this detection, the team searched for light emitted by dust grains in a distant galaxy, 9io9. Galaxies are packed full of dust grains and when a magnetic field is present, the grains tend to align and the light they emit becomes polarised. This means that the light waves oscillate along a preferred direction rather than randomly. When ALMA detected and mapped a polarised signal coming from 9io9, the presence of a magnetic field in a very distant galaxy was confirmed for the first time.

“No other telescope could have achieved this,” says Geach. The hope is that with this and future observations of distant magnetic fields the mystery of how these fundamental galactic features form will begin to unravel.

Large-scale Evolution of Seconds-long Relativistic Jets from Black Hole-Neutron Star Mergers

by Ore Gottlieb, Danat Issa, Jonatan Jacquemin-Ide, et al in Astrophysical Journal

Last year, Northwestern University researchers reported new observational evidence that long gamma-ray bursts (GRBs) can result from the merger of a neutron star with another compact object (either another neutron star or black hole) — a finding that was previously believed to be impossible.

Now, another Northwestern team offers a potential explanation for what generated the unprecedented and incredibly luminous burst of light. After developing the first numerical simulation that follows the jet evolution in a black hole-neutron star merger out to large distances, the astrophysicists discovered that the post-merger black hole can launch jets of material from the swallowed neutron star.

But the key ingredients are the mass of the violent whirlpool of gas (or accretion disk) surrounding the black hole and the strength of the disk’s magnetic field. In massive disks, when the magnetic field is strong, the black hole launches a short-duration jet that is much brighter than anything ever seen in observations. When the massive disk has a weaker magnetic field, however, the black hole launches a jet with the same luminosity and long duration as the mysterious GRB (dubbed GRB211211A) spotted in 2021 and reported in 2022. Not only does the new discovery help explain the origins of long GRBs, it also gives insight into the nature and physics of black holes, their magnetic fields and accretion disks.

“So far, no one else has developed any numerical works or simulations that consistently follow a jet from the compact-object merger to the formation of the jet and its large-scale evolution,” said Northwestern’s Ore Gottlieb, who co-led the work. “The motivation for our work was to do this for the first time. And what we found just so happened to match observations of GRB211211A.”
“Neutron-star mergers are a captivating multi-messenger phenomena, which result in both gravitational and electromagnetic waves,” said Northwestern’s Danat Issa, who co-led the work with Gottlieb. “However, simulating these events poses a challenge due to the vast spatial and temporal scale separations involved as well as the diverse physics operating across these scales. For the first time, we have succeeded in comprehensively modeling the entire sequence of the neutron star merger process.”

During the research, Gottlieb was a CIERA Fellow at Northwestern’s Center for Interdisciplinary Exploration and Research in Astrophysics (CIERA); now he is a Flatiron Research Fellow at the Flatiron Institute’s Center for Computational Astrophysics. Issa is a graduate student in the Department of Physics and Astronomy at Northwestern’s Weinberg College of Arts and Sciences and member of CIERA. Issa is advised by paper co-author Alexander Tchekhovskoy, an associate professor of physics and astronomy at Weinberg and member of CIERA.

When astronomers first spotted GRB211211A in December 2021, they initially assumed that the 50-second-long event was generated from the collapse of a massive star. But, as they examined the long GRB’s late-time emission, called the afterglow, they uncovered evidence of a kilonova, a rare event that only occurs after the merger of a neutron star with another compact object. The finding (published in Nature in December 2022) upended the long-established, long-accepted belief that only supernovae could generate long GRBs.

“GRB 211211A reignited interest in the origin of long-duration GRBs that are not associated with massive stars, but likely originating from compact binary mergers,” Gottlieb said.

Gamma-ray burst 211211A, the location of which is circled in red. Image by NASA, ESA, Rastinejad et al.

To further reveal what occurs during compact-merger events, Gottlieb, Issa and their collaborators sought to simulate the whole process — from before the merger all the way through to the end of the GRB event, when the GRB-producing jets shut off. Because it is such an incredibly computationally expensive feat, the entire scenario had never been modeled before. Gottlieb and Issa overcame that challenge by dividing the scenario into two simulations.

First, the researchers ran a simulation of the pre-merger phase. Then, they took the output from the first simulation and plugged it into the post-merger simulation.

“Because the space-time used by the two simulations is different, this remap was not as straightforward as we had hoped, but Danat figured it out,” Tchekhovskoy said.
“The daisy chaining of the two simulations allowed us to make the computation much less expensive,” Gottlieb said. “The physics is very complicated in the pre-merger stage because there are two objects. It gets much simpler after the pre-merger because there is only one black hole.”

In the simulation, the compact objects first merged to create a more massive black hole. The black hole’s intense gravity pulled the now-destroyed neutron star’s debris toward it. Before the debris fell into the black hole, some of the debris first swirled around the black hole as an accretion disk. In the configuration studied, the emerging disk was particularly massive with one-tenth the mass of our sun. Then, when the mass fell into the black hole from the disk, it powered the black hole to launch a jet that accelerated to near light speed.

A surprise emerged as the researchers adjusted the strength of the massive disk’s magnetic field. Whereas a strong magnetic field resulted in a short, incredibly bright GRB, a weak magnetic field generated a jet that matched observations of long GRBs.

“The stronger the magnetic field, the shorter is its lifetime,” Gottlieb said. “Weak magnetic fields produce weaker jets that the newly formed black hole can sustain for a longer time. A key ingredient here is the massive disk that can maintain, together with weak magnetic fields, a GRB consistent with observations and comparable to the luminosity and long duration of GRB211211A. Although we found this specific binary system to give rise to a long GRB, we also expect that other binary mergers that produce massive disks will lead to a similar outcome. It’s simply a question of the post-merger disk mass.”

Of course, “long” is relative in this scenario. GRBs are divided into two classes. GRBs with durations less than two seconds are considered short. If a GRB is two seconds or longer, then it’s considered long. Even events this brief are still exceptionally difficult to model.

“A major portion of this disk material ultimately gets consumed by the black hole, with the whole process lasting mere seconds,” Issa said. “Here lies the main challenge: It is very difficult to capture the evolution of these mergers, using simulations on supercomputers, over a span of several seconds.”

Evolution of Neptune at near-infrared wavelengths from 1994 through 2022

by Erandi Chavez, Imke de Pater, Erin Redwing, et al in Icarus

Astronomers have uncovered a link between Neptune’s shifting cloud abundance and the 11-year solar cycle, in which the waxing and waning of the Sun’s entangled magnetic fields drives solar activity.

This discovery is based on three decades of Neptune observations captured by NASA’s Hubble Space Telescope and the W. M. Keck Observatory in Hawaii, as well as data from the Lick Observatory in California. The link between Neptune and solar activity is surprising to planetary scientists because Neptune is our solar system’s farthest major planet and receives sunlight with about 0.1% of the intensity Earth receives. Yet Neptune’s global cloudy weather seems to be driven by solar activity, and not the planet’s four seasons, which each last approximately 40 years. At present, the cloud coverage seen on Neptune is extremely low, with the exception of some clouds hovering over the giant planet’s south pole. A University of California (UC) Berkeley-led team of astronomers discovered that the abundance of clouds normally seen at the icy giant’s mid-latitudes started to fade in 2019.

“I was surprised by how quickly clouds disappeared on Neptune,” said Imke de Pater, emeritus professor of astronomy at UC Berkeley and senior author of the study. “We essentially saw cloud activity drop within a few months,” she said.
“Even now, four years later, the most recent images we took this past June still show the clouds haven’t returned to their former levels,” said Erandi Chavez, a graduate student at the Center for Astrophysics | Harvard-Smithsonian (CfA) in Cambridge, Massachusetts, who led the study when she was an undergraduate astronomy student at UC Berkeley. “This is extremely exciting and unexpected, especially since Neptune’s previous period of low cloud activity was not nearly as dramatic and prolonged.”

To monitor the evolution of Neptune’s appearance, Chavez and her team analyzed Keck Observatory images taken from 2002 to 2022, the Hubble Space Telescope archival observations beginning in 1994, and data from the Lick Observatory in California from 2018 to 2019.

This sequence of Hubble Space Telescope images chronicles the waxing and waning of the amount of cloud cover on Neptune. This long set of observations shows that the number of clouds grows increasingly following a peak in the solar cycle — where the Sun’s level of activity rhythmically rises and falls over an 11-year period. Credits: NASA, ESA, Erandi Chavez (UC Berkeley), Imke de Pater (UC Berkeley)

In recent years, the Keck observations have been complemented by images taken as part of the Twilight Zone program and by Hubble’s Outer Planet Atmospheres Legacy (OPAL) program. The images reveal an intriguing pattern between seasonal changes in Neptune’s cloud cover and the solar cycle — the period when the Sun’s magnetic field flips every 11 years as it becomes more tangled like a ball of yarn. This is evident in the increasing number of sunspots and increasing solar flare activity. As the cycle progresses, the Sun’s tempestuous behavior builds to a maximum, until the magnetic field beaks down and reverses polarity. Then the Sun settles back down to a minimum, only to start another cycle.

When it’s stormy weather on the Sun, more intense ultraviolet (UV) radiation floods the solar system. The team found that two years after the solar cycle’s peak, an increasing number of clouds appear on Neptune. The team further found a positive correlation between the number of clouds and the ice giant’s brightness from the sunlight reflecting off it.

“These remarkable data give us the strongest evidence yet that Neptune’s cloud cover correlates with the Sun’s cycle,” said de Pater. “Our findings support the theory that the Sun’s UV rays, when strong enough, may be triggering a photochemical reaction that produces Neptune’s clouds.”

Scientists discovered the connection between the solar cycle and Neptune’s cloudy weather pattern by looking at 2.5 cycles of cloud activity recorded over the 29-year span of Neptunian observations. During this time, the planet’s reflectivity increased in 2002 then dimmed in 2007. Neptune became bright again in 2015, then darkened in 2020 to the lowest level ever observed, which is when most of the clouds went away. The changes in Neptune’s brightness caused by the Sun appear to go up and down relatively in sync with the coming and going of clouds on the planet. However there is a two-year time lag between the peak of the solar cycle and the abundance of clouds seen on Neptune. The chemical changes are caused by photochemistry, which happens high in Neptune’s upper atmosphere and takes time to form clouds.

“It’s fascinating to be able to use telescopes on Earth to study the climate of a world more than 2.5 billion miles away from us,” said Carlos Alvarez, staff astronomer at Keck Observatory and co-author of the study. “Advances in technology and observations have enabled us to constrain Neptune’s atmospheric models, which are key to understanding the correlation between the ice giant’s climate and the solar cycle.”

However, more work is necessary. For example, while an increase in UV sunlight could produce more clouds and haze, it could also darken them, thereby reducing Neptune’s overall brightness. Storms on Neptune rising up from the deep atmosphere affect the cloud cover, but are not related to photochemically produced clouds, and hence may complicate correlation studies with the solar cycle. Continued observations of Neptune are also needed to see how long the current near-absence of clouds will last.

The research team continues to track Neptune’s cloud activity. “We have seen more clouds in the most recent Keck images that were taken during the same time NASA’s James Webb Space Telescope observed the planet; these clouds were in particular seen at northern latitudes and at high altitudes, as expected from the observed increase in the solar UV flux over the past approximately 2 years,” said de Pater.

TOI-4600 b and c: Two Long-period Giant Planets Orbiting an Early K Dwarf

by Ismael Mireles, Diana Dragomir, Hugh P. Osborn, et al in The Astrophysical Journal Letters

Scientists from The University of New Mexico (UNM), and Massachusetts Institute of Technology (MIT) have detected and validated two of the longest-period exoplanets found by TESS to date. These long period large exoplanets orbit a K dwarf star and belong to a class of planets known as warm Jupiters, which have orbital periods of 10–200 days and are at least six times Earth’s radius. This recent discovery offers exciting research opportunities for the future of finding long-period planets that resemble those in our own solar system.

The exoplanets, TOI-4600 b and c, were detected using photometric data from the Transiting Exoplanet Survey Satellite (TESS) and followed up with observations using the telescopes on the ground since they provide better resolution. The observing strategy adopted by NASA’s TESS, which divides each hemisphere into 13 sectors that are surveyed for roughly 28 days, is producing the most comprehensive all-sky search for transiting planets. This approach has already proven its capability to detect both large and small planets around different kinds of stars. In the case of TOI-4600, the star is a K dwarf star, also known as an orange dwarf, which are stars slightly smaller and cooler than the Sun.

Exoplanets must transit their host stars at least twice within TESS ‘s observing span to be detected with the correct period by the Science Processing Operations Center (SPOC) pipeline and the Quick Look Pipeline (QLP), which search the 2-minute and 30-minute cadence TESS data, respectively. Because 74 percent of TESS’ total sky coverage is only observed for 28 days, the majority of TESS exoplanets detected have periods less than 40 days. Therefore, TOI-4600 b’s 82.69-day, or nearly 3-month, and TOI-4600 c’s 482.82-day, or 16-month, periods make their discoveries even more valuable.

The University of New Mexico’s Ismael Mireles, the lead author of the paper, along with collaborators including Diana Dragomir, an assistant professor in UNM’s Department of Physics and Astronomy, and collaborators from Massachusetts Institute of Technology and University of Bern, analyzed the data in order to measure the periods and sizes of these planets.

After initially detecting the transits, Mireles and team had to confirm that these were actual planets and to determine which signal the star was coming from. The diagnostic tools with TESS indicated that the signals coming from the target site were indeed on point. With help from TESS-Follow-up Observing Program (TFOP) Subgroup 1 (SG1), a global network of professional and amateur astronomers with access to telescopes small and large, they observed and watched a transit happen thus confirming for the researchers that this planet is indeed on target. Another factor that Mireles and his team had to consider were the masses and sizes of the planets. In order to achieve this they substituted the velocity measurements to observe how much the host star wobbles because the host star will pull on the planet.

“When we got the measurements, we were seeing very little movement in the target star. So when you start, you could be responsible for what we were seeing. Those two things together pretty much ruled it out. At that point we were sure that we had two planets,” Mireles stated.

Top: full TESS PDCSAP light curve of TOI-4600 showing four clear transits of TOI-4600 b and two transits of TOI-4600 c. An additional transit of TOI-4600 b is obscured by a sudden systematic increase in flux due to scattered light near TBJD 1850 while another transit at TBJD 2750 is obscured by a transit of TOI-4600 c that occurs 1.5 days later. Another transit of TOI-4600 b near TBJD 2419 occurred during a downlink gap and thus was not observed by TESS. The apparent difference in the transit depths is due to the different time resolutions, with the left portion showing 30 minute data and the middle and right portions showing 2 minute data. Bottom left: phase-folded detrended 2 (gray) and 30 minute (black) TESS data and best-fit model for TOI-4600 b. Bottom right: same as the bottom left but for TOI-4600 c.

The researchers found these two planets and the inner planet TOI-4600 b is 82.69 days with a radius that is around just under seven times Earth’s radius. It is between the size of Neptune and Saturn. This planet, TOI-4600 b,has an estimated temperature of about 170 degrees Fahrenheit, which is hot, but colder than a lot of the planets that astronomers have found. The second planet found, TOI-4600 c, is about nine and a half times Earth’s radius, meaning it is roughly Saturn sized. It initially transited only once the first time TESS observed the star before transiting a second time almost three years later.

“Once you have two transits, you have an idea of what the periods can be. It could be the 965 days separating them, half of that, a third, a quarter, etc. The shorter periods could be ruled out because TESS had observed the star for a long time, so it only left two periods: 965 days or half of that,” explained Mireles. The researchers used a model developed by collaborator Hugh Osborn at the University of Bern to compare the possible orbital periods and determine which one was most likely, and found that half of 965, or 482.82 days to be precise, was more likely. TOI-4600 c’s 482.82 day period makes it the longest-period planet found by TESS to date and with a temperature of around -110 degrees Fahrenheit, it is one of the coldest planets found by TESS.

Katharine Hesse, TOI & Vetting Lead at MIT, collaborated with Mireles and team on the data analysis from TESS. Hesse helped process and analyze the large amount of data and placed the system into the context of other multiple-planet systems that have been found by missions including TESS. The comparison of the TOI-4600 system with other discovered exoplanet systems helps explore features like the formation time and processes and helped the researchers begin to place this system in the broader context of exoplanet systems.

“The main thing is trying to uncover more about planet formation because based on what we know about the exoplanets we found, so far, nothing really looks like the solar system. The interesting thing is that we want to learn about this planet formation. We have over 5,000 exoplanets now, but none of these systems really look like the solar system. And so we want to find out how these different types of systems formed and migrated,” Mireles said.

Mireles and researchers are interested in these findings because of the discovery of two long period giant planets, which is a configuration that astronomers don’t often see, even though the solar system found had four giant long distances or a long period one. This prompts further research discussions and questions as Mireles points out, “We want to find out how these are formed? Are there other planets in this system? Does that tell us anything about how these giant planets affect smaller planets that might be in there or might not be in there and why they’re not there? There’s still things that we want to find out and that will tell us a lot about planet formation.”

In closing, Mireles promotes a call to action for citizen scientists, and hobbyists in astronomy, to participate and get involved in this research discovery. On Monday, Oct. 16, there will be another possible transit opportunity coming up for those who are interested and want to observe it to further confirm that the period of the outer planet is indeed 482 days. People with even smaller telescopes could participate if they have the right tools. “There are definitely people that are citizen scientists or amateur astronomers that have their own telescopes and help us with all these observations. There is a group of people with access to telescopes that are essentially confirming that a transit event is occurring on the star of interest,” said Mireles.

“People, who are either retired or have a different day job but who are also amateur astronomers, are contributing very useful data to help verify these planets. The results that they are producing are of professional quality. The efforts of these committed citizen scientists are critical to the process of confirming these planets” Dragomir, assistant professor in UNM’s Department of Physics and Astronomy stated.

Biofilm formation of Pseudomonas aeruginosa in spaceflight is minimized on lubricant impregnated surfaces

by Pamela Flores, Samantha A. McBride, Jonathan M. Galazka, Kripa K. Varanasi, Luis Zea in npj Microgravity

After exposure in space aboard the International Space Station, a new kind of surface treatment significantly reduced the growth of biofilms, scientists report. Biofilms are mats of microbial or fungal growth that can clog hoses or filters in water processing systems, or potentially cause illness in people.

In the experiment, researchers investigated a variety of surfaces treated in different ways and exposed to a bacteria called Pseudomonas aeruginosa, which is an opportunistic pathogen than can cause infections in humans, especially in hospitals. The surfaces were incubated for three days aboard the space station, starting in 2019. The results show that textured surfaces impregnated with a lubricant were highly successful at preventing biofilm growth during their long exposure in space. The findings are described by Samantha McBride PhD ’20 and Kripa Varanasi of MIT, Pamela Flores and Luis Zea at the University of Colorado, and Jonathan Galakza at NASA Ames Research Center.

Clogs in water recovery system hoses aboard the ISS have been so severe at times, the hoses had to be sent back to Earth for cleaning and refurbishing. And while it isn’t known whether biofilms have directly contributed to astronaut illnesses, on Earth, biofilms are associated with 65 percent of microbial infections, and 80 percent of chronic infections, the researchers say.

One approach to preventing biofilms is to use surfaces coated with certain metals or oxides that kill microbes, but this approach can fail when a layer of dead microbes builds up on the surface and allows biofilm to form above it. But this was not the case with the liquid-infused surface that performed well in the ISS experiments: Rather than killing the microbes, it prevented them from adhering to the surface in the first place.

The specific surface used was made of silicon that was etched to produce a nanoscale forest of pillars. This spiky surface is then infused with a silicon oil, which is drawn into the texture and held in place by capillary action, leaving a smooth and highly slippery surface that significantly reduces the adhesion of microbes and prevents them from forming a biofilm.

Inside these vials are chambers containing the new surface material and the microbes. They were launched in stasis to ISS to avoid bacterial growth before reaching microgravity conditions. Once in ISS, the astronauts activated the samples by combining the various chambers in the vials. Image: Space Biofilm Program

Identical experiments were conducted on Earth as well as on the space station to determine the differences produced by the microgravity environment in orbit. To the researchers’ surprise, the liquid-infused surface performed even better in space than it did on Earth at preventing microbial adhesion.

On previous and current space stations, including the USSR’s Mir station, Salyut 6, and Salyut 7, as well as the International Space Station, “they’ve seen these biofilms, and they jeopardize a variety of instruments or equipment, including space suits, recycling units, radiators, and water treatment facilities, so it’s a very important problem that needed to be understood,” says Varanasi, a professor of mechanical engineering and founder of a company called LiquiGlide, which makes liquid-impregnated surfaces for containers to help their contents slide out.

Previous tests on Earth had shown that these treated surfaces could significantly reduce biofilm adhesion. When the samples from the space station were retrieved and tested, “we found that these surfaces are extremely good at preventing biofilm formation in the space station as well,” Varanasi says. This is important because past work has found that microgravity can have a significant influence on biofilm morphologies, attachment behavior, and gene expression, according to McBride. Thus, strategies that work well on Earth for biofilm mitigation may not necessarily be applicable to microgravity situations.

Preventing biofilms will be especially important for future long-duration missions, such as to the moon or Mars, where the option of quickly returning fouled equipment or sick astronauts to Earth will not be available, the team says. If further testing confirms its long-term stability and successful biofilm prevention, coatings based on the liquid-treated surface concept could be applied to a variety of critical components that are known to be susceptible to biofilm fouling, such as water treatment hoses and filters, or to parts that come in close contact with astronauts, such as gloves or food preparation surfaces.

In the terrestrial samples, biofilm formation was reduced by about 74 percent, while the space station samples showed a reduction of about 86 percent, says Flores, who did much of the testing of the ISS-exposed samples. “The results we got were surprising,” she says, because earlier tests carried out by others had shown biofilm formation was actually greater in space than on Earth. “We actually found the opposite on these samples,” she says.

While the tests used a specific and well-studied gram-negative kind of bacteria, she says, the results should apply to any kind of gram-negative bacteria, and likely to gram-positive bacteria as well. They found that the areas of the surface where no bacterial growth took place were covered by a thin layer of nucleic acids, which have a slight negative electric charge that may have helped to prevent microbes from adhering. Both gram-positive and gram-negative bacteria have a slight negative charge, which could repel them from that negatively charged surface, Flores says.

Other types of anti-fouling surfaces, Varanasi says, “work mostly on a biocidal property, which usually only works for a first layer of cells because after those cells die they can form a deposit, and microbes can grow on top of them. So, usually it’s been a very hard problem.” But with the liquid-impregnated surface, where what is exposed is mostly just the liquid itself, there are very few defects or points where the bacteria can find a footing, he says.

Although the test material was on the space station for more than a year, the actual tests were only performed over a three-day period because they required active participation by the astronauts whose schedules are always very busy. But one recommendation the team has made, based on these initial results, is that longer-duration tests should be carried out on a future mission. In these first tests, Flores says, the results after the third day looked the same as after the first and second days. “We don’t know for how long it will be able to keep up this performance, so we definitely recommend a longer time of incubation, and also, if possible, a continuous analysis, and not just end points.”

Zea, who initiated the project with NASA, says that this was the first time the agency has conducted tests that involved joint participation by two of its science programs, biology and physical sciences. “I think it stresses the importance of multidisciplinarity because we need to be able to combine these different disciplines to find solutions to real world problems.”

Biofilms are also a significant medical issue on Earth, especially on medical devices or implants including catheters, where they can lead to significant disease problems. The same kind of liquid-impregnated surfaces may have a role to play in helping to address these issues, Varanasi says.

Matter ejections behind the highs and lows of the transitional millisecond pulsar PSR J1023+0038

by M. C. Baglio, F. Coti Zelati, S. Campana, G. Busquet, et al in Astronomy & Astrophysics

With a remarkable observational campaign that involved 12 telescopes both on the ground and in space, including three European Southern Observatory (ESO) facilities, astronomers have uncovered the strange behaviour of a pulsar, a super-fast-spinning dead star. This mysterious object is known to switch between two brightness modes almost constantly, something that until now has been an enigma. But astronomers have now found that sudden ejections of matter from the pulsar over very short periods are responsible for the peculiar switches.

“We have witnessed extraordinary cosmic events where enormous amounts of matter, similar to cosmic cannonballs, are launched into space within a very brief time span of tens of seconds from a small, dense celestial object rotating at incredibly high speeds,” says Maria Cristina Baglio, researcher at New York University Abu Dhabi, affiliated with the Italian National Institute for Astrophysics (INAF), and the lead author of the paper published today in Astronomy & Astrophysics.

A pulsar is a fast-rotating, magnetic, dead star that emits a beam of electromagnetic radiation into space. As it rotates, this beam sweeps across the cosmos — much like a lighthouse beam scanning its surroundings — and is detected by astronomers as it intersects the line of sight to Earth. This makes the star appear to pulse in brightness as seen from our planet.

PSR J1023+0038, or J1023 for short, is a special type of pulsar with a bizarre behaviour. Located about 4500 light-years away in the Sextans constellation, it closely orbits another star. Over the past decade, the pulsar has been actively pulling matter off this companion, which accumulates in a disc around the pulsar and slowly falls towards it.

Since this process of accumulating matter began, the sweeping beam virtually vanished and the pulsar started incessantly switching between two modes. In the ‘high’ mode, the pulsar gives off bright X-rays, ultraviolet and visible light, while in the ‘low’ mode it’s dimmer at these frequencies and emits more radio waves. The pulsar can stay in each mode for several seconds or minutes, and then switch to the other mode in just a few seconds. This switching has thus far puzzled astronomers.

“Our unprecedented observing campaign to understand this pulsar’s behaviour involved a dozen cutting-edge ground-based and space-borne telescopes,” says Francesco Coti Zelati, a researcher at the Institute of Space Sciences, Barcelona, Spain, and co-lead author of the paper. The campaign included ESO’s Very Large Telescope (VLT) and ESO’s New Technology Telescope (NTT), which detected visible and near-infrared light, as well as the Atacama Large Millimeter/submillimeter Array (ALMA), in which ESO is a partner. Over two nights in June 2021, they observed the system make over 280 switches between its high and low modes.

Temporal evolution of the X-ray, UV, optical, NIR, and radio emissions of J1023 on the night of 2021 June 3–4.

“We have discovered that the mode switching stems from an intricate interplay between the pulsar wind, a flow of high-energy particles blowing away from the pulsar, and matter flowing towards the pulsar,” says Coti Zelati, who is also affiliated with INAF.

In the low mode, matter flowing towards the pulsar is expelled in a narrow jet perpendicular to the disc. Gradually, this matter accumulates closer and closer to the pulsar and, as this happens, it is hit by the wind blowing from the pulsating star, causing the matter to heat up. The system is now in a high mode, glowing brightly in the X-ray, ultraviolet and visible light. Eventually, blobs of this hot matter are removed by the pulsar via the jet. With less hot matter in the disc, the system glows less brightly, switching back into the low mode.

While this discovery has unlocked the mystery of J1023’s strange behaviour, astronomers still have much to learn from studying this unique system and ESO’s telescopes will continue to help astronomers observe this peculiar pulsar. In particular, ESO’s Extremely Large Telescope (ELT), currently under construction in Chile, will offer an unprecedented view of J1023’s switching mechanisms. “The ELT will allow us to gain key insights into how the abundance, distribution, dynamics, and energetics of the inflowing matter around the pulsar are affected by the mode switching behavior,” concludes Sergio Campana, Research Director at the INAF Brera Observatory and coauthor of the study.