ST/ The planet that could end life on Earth

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Paradigm

30 min readMar 10, 2023

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Space biweekly vol.72, 23rd February — 10th March

TL;DR

A terrestrial planet hovering between Mars and Jupiter would be able to push Earth out of the solar system and wipe out life on this planet, according to a recent experiment.
Observations of water in the disk forming around protostar V883 Ori have unlocked clues about the formation of comets and planetesimals in our own solar system.
When asteroids suffer natural impacts in space, debris flies off from the point of impact. The tail of particles that form can help determine the physical characteristics of the asteroid. NASA’s Double Asteroid Redirection Test mission in September 2022 gave a team of scientists a unique opportunity — to observe the evolution of an asteroid’s ejecta as it happened.
Scientists identified about 140,000 molecular clouds in the Milky Way Galaxy from large-scale data of carbon monoxide molecules, observed in detail by the Nobeyama 45-m radio telescope. Using artificial intelligence, the researchers estimated the distance of each of these molecular clouds to determine their size and mass, successfully mapping the distribution of the molecular clouds in the Galaxy in the most detailed manner to date.
Scientists have detected the heaviest and youngest infant star ever discovered close to the black hole at the center of our Galaxy. They also identified the region where this ‘impossible star’ may have formed.
A liquid nitrogen spray can remove almost all of the simulated moon dust from a space suit, potentially solving what is a significant challenge for future moon-landing astronauts.
Using data from the James Webb Space Telescope’s first year of interstellar observation, an international team of researchers was able to serendipitously view an exploding supernova in a faraway spiral galaxy.
An object near the supermassive black hole at the center of the Milky Way galaxy has drawn the interest of scientists because it has evolved dramatically in a relatively short time. A new study suggests that the object, called X7, could be a cloud of dust and gas that was created when two stars collided. The researchers believe it will eventually be drawn toward the black hole and will disintegrate.
Astronomers have discovered a rapidly growing black hole in one of the most extreme galaxies known in the very early Universe. The discovery of the galaxy and the black hole at its center provides new clues on the formation of the very first supermassive black holes.
Enceladus, the sixth largest of Saturn’s moons, is known for spraying out tiny icy silica particles — so many of them that the particles are a key component of the second outermost ring around Saturn. Scientists have not known how that happens or how long the process takes. A study now shows that tidal heating in Enceladus’ core creates currents that transport the silica, which is likely released by deep-sea hydrothermal vents, over the course of just a few months.
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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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The Dynamical Consequences of a Super-Earth in the Solar System

by Stephen R. Kane in The Planetary Science Journal

A terrestrial planet hovering between Mars and Jupiter would be able to push Earth out of the solar system and wipe out life on this planet, according to a UC Riverside experiment.

UCR astrophysicist Stephen Kane explained that his experiment was meant to address two notable gaps in planetary science.

The first is the gap in our solar system between the size of terrestrial and giant gas planets. The largest terrestrial planet is Earth, and the smallest gas giant is Neptune, which is four times wider and 17 times more massive than Earth. There is nothing in between.

Top-down view of the solar system planetary orbits (shown as solid lines) out to the orbit of Jupiter. The red shaded region indicates the locations in which a planet in the mass range 1–10 M⊕ was added to the solar system architecture. The dotted lines show a grid with 1 au resolution; the full figure scale is 12 au along one side.

“In other star systems there are many planets with masses in that gap. We call them super-Earths,” Kane said.

The other gap is in location, relative to the sun, between Mars and Jupiter. “Planetary scientists often wish there was something in between those two planets. It seems like wasted real estate,” he said.

These gaps could offer important insights into the architecture of our solar system, and into Earth’s evolution. To fill them in, Kane ran dynamic computer simulations of a planet between Mars and Jupiter with a range of different masses, and then observed the effects on the orbits of all other planets. The results were mostly disastrous for the solar system.

“This fictional planet gives a nudge to Jupiter that is just enough to destabilize everything else,” Kane said. “Despite many astronomers having wished for this extra planet, it’s a good thing we don’t have it.”

Semimajor axis evolution, expressed as a fractional change from the initial value, of the solar system terrestrial planets (top four panels) for a 107 yr simulation, where the additional planet (bottom panel) has a mass and semimajor axis of 7.0 M⊕ and 2.00 au, respectively.

Jupiter is much larger than all the other planets combined; its mass is 318 times that of Earth, so its gravitational influence is profound. If a super-Earth in our solar system, a passing star, or any other celestial object disturbed Jupiter even slightly, all other planets would be profoundly affected. Depending on the mass and exact location of a super-Earth, its presence could ultimately eject Mercury and Venus as well as Earth from the solar system. It could also destabilize the orbits of Uranus and Neptune, tossing them into outer space as well.

The super-Earth would change the shape of this Earth’s orbit, making it far less habitable than it is today, if not ending life entirely. If Kane made the planet’s mass smaller and put it directly in between Mars and Jupiter, he saw it was possible for the planet to remain stable for a long period of time. But small moves in any direction and, “things would go poorly,” he said.

Intensity plot showing the ratio of eccentricity variation amplitude to those from the baseline solar system model, as a function of added planet mass and semimajor axis. Results are shown for Earth (top panel) and Mars (bottom panel).

The study has implications for the ability of planets in other solar systems to host life. Though Jupiter-like planets, gas giants far from their stars, are only found in about 10% of the time, their presence could decide whether neighboring Earths or super-Earths have stable orbits.

These results gave Kane a renewed respect for the delicate order that holds the planets together around the sun. “Our solar system is more finely tuned than I appreciated before. It all works like intricate clock gears. Throw more gears into the mix and it all breaks,” Kane said.

Deuterium-enriched water ties planet-forming disks to comets and protostars

by Tobin, J.J., van ’t Hoff, M.L.R., Leemker, M. et al. in Nature

Scientists studying a nearby protostar have detected the presence of water in its circumstellar disk. The new observations made with the Atacama Large Millimeter/submillimeter Array (ALMA) mark the first detection of water being inherited into a protoplanetary disk without significant changes to its composition. These results further suggest that the water in our Solar System formed billions of years before the Sun.

V883 Orionis is a protostar located roughly 1,305 light-years from Earth in the constellation Orion. The new observations of this protostar have helped scientists to find a probable link between the water in the interstellar medium and the water in our Solar System by confirming they have similar composition.

“We can think of the path of water through the Universe as a trail. We know what the endpoints look like, which are water on planets and in comets, but we wanted to trace that trail back to the origins of water,” said John Tobin, an astronomer at the National Science Foundation’s National Radio Astronomy Observatory (NRAO) and the lead author on the new paper. “Before now, we could link the Earth to comets, and protostars to the interstellar medium, but we couldn’t link protostars to comets. V883 Ori has changed that, and proven the water molecules in that system and in our Solar System have a similar ratio of deuterium and hydrogen.”

Channel maps of HDO 225 and 241 GHz emission.

Observing water in the circumstellar disks around protostars is difficult because in most systems water is present in the form of ice. When scientists observe protostars they’re looking for the water snow line or ice line, which is the place where water transitions from predominantly ice to gas, which radio astronomy can observe in detail.

“If the snow line is located too close to the star, there isn’t enough gaseous water to be easily detectable and the dusty disk may block out a lot of the water emission. But if the snow line is located further from the star, there is sufficient gaseous water to be detectable, and that’s the case with V883 Ori,” said Tobin, who added that the unique state of the protostar is what made this project possible.

V883 Ori’s disk is quite massive and is just hot enough that the water in it has turned from ice to gas. That makes this protostar an ideal target for studying the growth and evolution of solar systems at radio wavelengths.

“This observation highlights the superb capabilities of the ALMA instrument in helping astronomers study something vitally important for life on Earth: water,” said Joe Pesce, NSF Program Officer for ALMA. “An understanding of the underlying processes important for us on Earth, seen in more distant regions of the galaxy, also benefits our knowledge of how nature works in general, and the processes that had to occur for our Solar System to develop into what we know today.”

To connect the water in V883 Ori’s protoplanetary disk to that in our own Solar System, the team measured its composition using ALMA’s highly sensitive Band 5 (1.6mm) and Band 6 (1.3mm) receivers and found that it remains relatively unchanged between each stage of solar system formation: protostar, protoplanetary disk, and comets.

“This means that the water in our Solar System was formed long before the Sun, planets, and comets formed. We already knew that there is plenty of water ice in the interstellar medium. Our results show that this water got directly incorporated into the Solar System during its formation,” said Merel van ‘t ‘Hoff, an astronomer at the University of Michigan and a co-author of the paper. “This is exciting as it suggests that other planetary systems should have received large amounts of water too.”

V883 Ori is a unique protostar whose temperature is just hot enough that the water in its circumstellar disk has turned to gas, making it possible for radio astronomers to trace the water’s origins.

Clarifying the role of water in the development of comets and planetesimals is critical to building an understanding of how our own Solar System developed. Although the Sun is believed to have formed in a dense cluster of stars and V883 Ori is relatively isolated with no nearby stars, the two share one critical thing in common: they were both formed in giant molecular clouds.

“It is known that the bulk of the water in the interstellar medium forms as ice on the surfaces of tiny dust grains in the clouds. When these clouds collapse under their own gravity and form young stars, the water ends up in the disks around them. Eventually, the disks evolve and the icy dust grains coagulate to form a new solar system with planets and comets,” said Margot Leemker, an astronomer at Leiden University and a co-author of the paper. “We have shown that water that is produced in the clouds follows this trail virtually unchanged. So, by looking at the water in the V883 Ori disk, we essentially look back in time and see how our own Solar System looked when it was much younger.”
Tobin added, “Until now, the chain of water in the development of our Solar System was broken. V883 Ori is the missing link in this case, and we now have an unbroken chain in the lineage of water from comets and protostars to the interstellar medium.”

Ejecta from the DART-produced active asteroid Dimorphos

by Jian-Yang Li, Masatoshi Hirabayashi, Tony L. Farnham, et al in Nature

When asteroids suffer natural impacts in space, debris flies off from the point of impact. The tail of particles that form can help determine the physical characteristics of the asteroid. NASA’s Double Asteroid Redirection Test mission in September 2022 gave a team of scientists including Rahil Makadia, a Ph.D. student in the Department of Aerospace Engineering at the University of Illinois Urbana-Champaign, a unique opportunity — to observe the evolution of an asteroid’s ejecta as it happened for the first time.

“My work on this mission so far has been to study the heliocentric changes to the orbit of Didymos and its smaller moon Dimorphos — the target of the DART spacecraft,” said Makadia. “Even though it hit the secondary, there are still some changes in the entire system’s orbit around the sun because the entire system feels the consequences of the impact. The ejecta that escapes the system provides an extra boost in addition to the impact. So, to accurately determine where the system will be in 100 years, you need to know the contribution of the ejecta that escaped the system.”

The team observed a 33-minute change in the orbit after DART’s impact. Makadia said, if there were no ejecta, the period change would have been less than 33 minutes. But because some ejecta escaped the gravitational pull of Dimorphos, the orbit period change is higher than if there were no ejecta at all.

These three panels capture the breakup of the asteroid Dimorphos when it was deliberately hit by NASA’s 1,200-pound Double Asteroid Redirection Test mission spacecraft on September 26, 2022. Hubble Space Telescope had a ringside view of the space demolition derby. The top panel, taken 2 hours after impact, shows an ejecta cone of an estimated 1,000 tons of dust. The center frame shows the dynamic interaction within the asteroid’s binary system that starts to distort the cone shape of the ejecta pattern about 17 hours after the impact. The most prominent structures are rotating, pinwheel-shaped features. The pinwheel is tied to the gravitational pull of the companion asteroid, Didymos. In the bottom frame Hubble next captures the debris being swept back into a comet-like tail by the pressure of sunlight on the tiny dust particles. This stretches out into a debris train where the lightest particles travel the fastest and farthest from the asteroid. The mystery is compounded when Hubble records the tail splitting in two for a few days.

The study focused on the Hubble Space Telescope’s measurements of the ejecta, beginning 15 minutes after the impact to 18 ½ days after the impact. The images showed the exact evolution of the tail and how it evolved over time.

“After a few days, the primary force acting on these ejecta particles becomes solar radiation pressure,” Makadia said. “The photons emitted from the sun exert an acceleration on these small particles, and they evolve into a straight tail in an anti-solar direction.
“There have been cases in which it was determined that a natural impact caused the observed active asteroid. But because this one was very much intended, we could have telescopes pointed at it before and after the impact and study its evolution.”

He said they’ll use the data about how this ejecta evolves to understand how the entire system’s orbit changes as well.

“Now that we have this treasure trove of data, we can make educated guesses about other tails we might observe,” Makadia said. “Depending on what kind of particles are in the tail and their sizes, we can figure out how long ago that impact happened. And we’ll be able to understand the ejecta that escape the system and change the entire system’s heliocentric orbit.”

Makadia, who earned his B.S. in 2020 from UIUC, said almost all of his work is computational.

“To calculate where an asteroid will be on a given date, we need to propagate all the possible locations that the asteroid could be at an initial time, not just one nominal solution. That requires a lot of computational power and understanding of how orbits are affected by small forces, like solar radiation pressure as well as gravity from all kinds of sources within the solar system.

Distance determination of molecular clouds in the first quadrant of the Galactic plane using deep learning: I. Method and results

by Shinji Fujita, Atsushi M Ito, Yusuke Miyamoto, et al in Publications of the Astronomical Society of Japan

Osaka Metropolitan University scientists identified about 140,000 molecular clouds in the Milky Way Galaxy from large-scale data of carbon monoxide molecules, observed in detail by the Nobeyama 45-m radio telescope. Using artificial intelligence, the researchers estimated the distance of each of these molecular clouds to determine their size and mass, successfully mapping the distribution of the molecular clouds in the Galaxy in the most detailed manner to date.

Stars are formed by molecular gas and dust coalescing in space. These molecular gases are so dilute and cold that they are invisible to the human eye, but they do emit faint radio waves that can be observed by radio telescopes.

The poster of the FUGIN (FOREST Unbiased Galactic plane Imaging survey with Nobeyama 45-m telescope) project (https://nro-fugin.github.io/). The upper panel shows the distribution of molecular clouds in the Milky Way Galaxy obtained by the Nobeyama 45-m radio telescope. The lower panel shows infrared observation by the Spitzer Space Telescope.

Observing from Earth, a lot of matter lies ahead and behind these molecular clouds and these overlapping features make it difficult to determine their distance and physical properties such as size and mass.

So, even though our Galaxy, the Milky Way, is the only galaxy close enough to make detailed observations of molecular clouds in the whole universe, it has been very difficult to investigate the physical properties of molecular clouds in a cohesive manner from large-scale observations.

X3: A High-mass Young Stellar Object Close to the Supermassive Black Hole Sgr A*

by Florian Peißker, Michal Zajaček, Nadeen B. Sabha, Masato Tsuboi, Jihane Moultaka, Lucas Labadie, Andreas Eckart, Vladimír Karas, Lukas Steiniger, Matthias Subroweit, Anjana Suresh, Maria Melamed, Yann Clénet in The Astrophysical Journal

An international team of researchers under the leadership of Dr Florian Peißker at the University of Cologne’s Institute of Astrophysics has discovered a very young star in its formation phase near the supermassive black hole Sagittarius A* (Sgr A*) at the centre of our Milky Way. The star is only several tens of thousands of years old, making it younger than humanity. The special thing about baby star X3a is that theoretically it should not be able to exist so close to the supermassive black hole in the first place. However, the team believes that it formed in a dust cloud orbiting the giant black hole and sank to its current orbit only after it had formed.

The vicinity of the black hole at the centre of our Galaxy is generally considered to be a region characterized by highly dynamic processes and hard X-ray and UV radiation. Precisely these conditions act against the formation of stars like our Sun. Therefore, for a long time scientists had assumed that over periods of billions of years, only old, evolved stars can settle by dynamical friction in the vicinity of the supermassive black hole. However, quite surprisingly, already twenty years ago very young stars were found in the immediate vicinity of Sgr A*. It is still not clear how these stars got there or where they formed. The occurrence of very young stars very close to the supermassive black hole has been referred to as “the paradox of youth.”

Finding chart for the X3 system. We show two zoomed views toward the X3 system. The cyan zoom box to the left shows a K- and L-band overlay image where blue represents the dust of the bow shock and red is associated with hot and thermal emission.

The baby star X3a — which is ten times as big and fifteen times as heavy as our Sun — could now close the gap between star formation and the young stars in the immediate vicinity of Sgr A*. X3a needs special conditions to form in the immediate vicinity of the black hole. First author Dr Florian Peißker explained: “It turns out that there is a region at a distance of a few light years from the black hole which fulfils the conditions for star formation. This region, a ring of gas and dust, is sufficiently cold and shielded against destructive radiation.” Low temperatures and high densities create an environment in which clouds of hundreds of solar masses can form. These clouds can in principle move very fast towards the direction of the black hole due to cloud-cloud collisions and scattering that remove the angular momentum.

In addition, very hot clumps formed in close proximity to the baby star which could then be accreted by X3a. These clumps could thus also contribute to X3a reaching such a high mass in the first place. However, these clumps are only a part of the formation history of X3a. They still do not explain its “birth.”

The scientists assume the following scenario to be possible: shielded from the gravitational influence of Sgr A* and intense radiation, a dense enough cloud could have formed in the outer gas and dust ring around the centre of the Galaxy. This cloud had a mass of about one hundred suns and collapsed under its own gravity to one or more protostars. “This so-called fall time approximately corresponds to the age of X3a,” Peißker added. Observations have shown that there are many of these clouds that can interact with each other. It is therefore likely that a cloud falls towards the black hole from time to time.

This scenario would also fit X3a’s stellar development phase, which is currently evolving into a mature star. It is therefore quite plausible that the gas and dust ring acts as the birthplace of the young stars in the centre of our Galaxy. Dr Michal Zaja?ek at Masaryk University in Brno (Czech Republic), a co-author of the study, clarified: “With its high mass of about ten times the Solar mass, X3a is a giant among stars, and these giants evolve very quickly towards maturity. We have been lucky to spot the massive star in the midst of the comet-shaped circumstellar envelope. Subsequently, we identified key features associated with a young age, such as the compact circumstellar envelope rotating around it.”

Since similar dust and gas rings can be found in other galaxies, the described mechanism could apply there as well. Many galaxies can therefore host very young stars in their very centres. Planned observations with NASA’s James Webb Space Telescope or the European Southern Observatory’s Extremely Large Telescope in Chile will test this star formation model for our Galaxy as well as others.

Lunar dust removal and material degradation from liquid nitrogen sprays

by I. Wells, J. Bussey, N. Swets, J. Leachman in Acta Astronautica

A liquid nitrogen spray developed by Washington State University researchers can remove almost all of the simulated moon dust from a space suit, potentially solving what is a significant challenge for future moon-landing astronauts.

The sprayer removed more than 98% of moon dust simulant in a vacuum environment with minimal damage to spacesuits, performing better than any techniques that have been investigated previously.

While people have managed to put men on the moon, they haven’t figured out how to keep them clean there. Similar to the clingiest packaging peanuts, moon dust sticks to everything that it touches. Worse than the packing peanuts, the dust is composed of very fine particles that are the consistency of ground fiberglass.

“Moon dust is electrostatically charged, abrasive and gets everywhere, making it a very difficult substance to deal with,” said Ian Wells, first author on the paper and a senior in WSU’s School of Mechanical and Materials Engineering. “You end up with a fine layer of dust as a minimum just covering everything.”

Cryoclastic flow caused by liquid nitrogen poured on lunar dust simulant.

During the six crewed Apollo missions to the moon in the 1960s and early 1970s, astronauts used a brush to try to remove the dust from their spacesuits, but it didn’t work very well. The abrasive and tiny dust particles can get into engines and electronics. They also got into the spacesuits, destroying their seals and making some of the expensive suits unusable. Astronauts also suffered from “lunar hay fever,” and researchers think that a longer exposure to the dust could cause lung damage similar to that of Black Lung Disease.

“It posed a lot of problems that affected the missions as well as the astronauts once they returned home,” said Wells.

The NASA Artemis mission aims to land the first woman and first person of color on the moon in 2025 with the hope of eventually setting up a base camp there for further planetary exploration, so they are interested in finding a solution to the moon dust problem.

In their work, the research team demonstrated their technology that uses the Leidenfrost Effect to clean the space suits. The effect can be seen when one pours cold water on a hot frying pan, where it beads up and moves across the pan. Spray the very cold liquid nitrogen at a warmer dust-covered material, and the dust particles bead up and float away on the nitrogen vapor.

The team tested their cleaning method under normal atmospheric conditions and in a vacuum that is more similar to outer space with the sprayer performing better in the vacuum atmosphere.

The liquid nitrogen spray was also much gentler on spacesuit materials than other cleaning methods. While a brush caused damage to the spacesuit material after just one brushing, the liquid nitrogen spray took 75 cycles before damage occurred.

Serendipitous Nebular-phase JWST Imaging of SN Ia SN 2021aefx: Testing the Confinement of 56Co Decay Energy

by Ness Mayker Chen, Michael A. Tucker, Nils Hoyer, Saurabh W. Jha, et al in The Astrophysical Journal Letters

Using data from the James Webb Space Telescope’s first year of interstellar observation, an international team of researchers was able to serendipitously view an exploding supernova in a faraway spiral galaxy.

The study provides new infrared measurements of one of the brightest galaxies in our cosmic neighborhood, NGC 1566, also known as the Spanish Dancer. Located about 40 million light-years away from Earth, the galaxy’s extremely active center has led it to become especially popular with scientists aiming to learn more about how star-forming nebulae form and evolve.

In this case, scientists were able to survey a Type 1a supernova — the explosion of a carbon-oxygen white dwarf star, which Michael Tucker, a fellow at the Center for Cosmology and AstroParticle Physics at The Ohio State University and a co-author of the study, said researchers caught by mere chance while studying NGC 1566.

“White dwarf explosions are important to the field of cosmology, as astronomers often use them as indicators of distance,” said Tucker. “They also produce a huge chunk of the iron group elements in the universe, such as iron, cobalt and nickel.”

The research was made possible thanks to the PHANGS-JWST Survey, which, due to its vast inventory of star cluster measurements, was used to create a reference dataset to study in nearby galaxies. By analyzing images taken of the supernova’s core, Tucker and co-author Ness Mayker Chen, a graduate student in astronomy at Ohio State who led the study, aimed to investigate how certain chemical elements are emitted into the surrounding cosmos after an explosion. For instance, light elements like hydrogen and helium were formed during the big bang, but heavier elements can be created only through the thermonuclear reactions that happen inside supernovas. Understanding how these stellar reactions affect the distribution of iron elements around the cosmos could give researchers deeper insight into the chemical formation of the universe, said Tucker.

SN 2021aefx in NGC 1566 at ≈2–21 μm. Left panel: MIRI F1130W PHANGS-JWST image of NGC 1566 showing the location of SN 2021aefx, marked with a green circle. Right panels: zoom-ins on SN 2021aefx in each PHANGS-JWST filter.

“As a supernova explodes, it expands, and as it does so, we can essentially see different layers of the ejecta, which allows us to probe the nebula’s core,” he said. Powered by a process called radioactive decay — wherein an unstable atom releases energy to become more stable — supernovas emit radioactive high-energy photons like uranium-238. In this instance, the study specifically focused on how the isotope cobalt-56 decays into iron-56.

Using data from JWST’s near-infrared and mid-infrared camera instruments to investigate the evolution of these emissions, researchers found that more than 200 days after the initial event, supernova ejecta was still visible at infrared wavelengths that would have been impossible to image from the ground.

“This is one of those studies where if our results weren’t what we expected, it would have been really concerning,” he said. “We’ve always made the assumption that energy doesn’t escape the ejecta, but until JWST, it was only a theory.”

For many years, it was unclear whether fast-moving particles produced when cobalt-56 decays into iron-56 seeped into the surrounding environment, or were held back by the magnetic fields supernovas create. Yet by providing new insight into the cooling properties of supernova ejecta, the study confirms that in most circumstances, ejecta doesn’t escape the confines of the explosion. This reaffirms many of the assumptions scientists have made in the past about how these complex entities work, Tucker said.

“This study validates almost 20 years’ worth of science,” he said. “It doesn’t answer every question, but it does a good job of at least showing that our assumptions haven’t been catastrophically wrong.”

Future JWST observations will continue to help scientists develop their theories about star formation and evolution, but Tucker said that further access to other types of imaging filters could help test them as well, creating more opportunities to understand wonders far beyond the edges of our own galaxy.

The Swansong of the Galactic Center Source X7: An Extreme Example of Tidal Evolution near the Supermassive Black Hole

by Anna Ciurlo, Randall D. Campbell, Mark R. Morris, et al in The Astrophysical Journal

For two decades, scientists have observed an elongated object named X7 near the supermassive black hole at the center of the Milky Way and wondered what it was. Was it pulled off a larger structure nearby? Was its unusual form the result of stellar winds or was it shaped by jets of particles from the black hole?

Now, having examined the evolution of X7 using 20 years of data gathered by the Galactic Center Orbit Inintiative, astronomers from the UCLA Galactic Center Group and the Keck Observatory propose that it could be a cloud of dust and gas that was ejected during the collision of two stars.

Over time, they report, X7 has stretched, and it is being pulled apart as the black hole drags it closer, exerting its tidal force upon the cloud. They expect that within the next few decades, X7 will disintegrate and the gas and dust of which it is composed will eventually be drawn toward the black hole, which is called Sagittarius A*, or Sgr A*.

“No other object in this region has shown such an extreme evolution,” said Anna Ciurlo, a UCLA assistant researcher and the paper’s lead author. “It started off comet-shaped and people thought maybe it got that shape from stellar winds or jets of particles from the black hole. But as we followed it for 20 years we saw it becoming more elongated. Something must have put this cloud on its particular path with its particular orientation.”

Defining the position, orientation, and profile of X7. Top left: NIRC2 2020 Lp image showing a series of cuts along X7 ridge. The central peak of each cut (shown as a red dot) is determined with a Gaussian. A linear fit to these peaks (green line) defines the ridge of X7, while the half-maximum along ridge profile defines the location of the tip (shown as a blue dot).

X7 has a mass of about 50 Earths and is on an orbital path around Sgr A* that would take 170 years to complete. But that might never happen. Based on its trajectory, the team estimates that X7 will make its closest approach to Sgr A* around the year 2036, and then likely spiral toward Sgr A* and disappear.

“We anticipate the strong tidal forces exerted by the galactic black hole will ultimately tear X7 apart before it completes even one orbit,” said co-author Mark Morris, UCLA professor of physics and astronomy.

Tidal forces are the gravitational pull that cause an object approaching a black hole to stretch; the side of the object closest to the black hole is pulled much more strongly than the opposite end. X7 shows some of the same properties as the other strange dusty objects orbiting Sgr A*. Those so-called G objects look like gas but behave like stars. But X7’s shape and velocity have changed more dramatically than G objects’ have. As it accelerates toward the black hole, X7 is moving rapidly, clocking in at speeds of up to around 700 miles per second.

“It’s exciting to see significant changes of X7’s shape and dynamics in such great detail over a relatively short time scale as the gravitational forces of the supermassive black hole at the center of the Milky Way influences this object,” Randy Campbell, a co-author of the paper and the science operations lead at the Keck Observatory, said in a statement.

Although X7’s origin is still the subject of debate, the finding suggests that it arose after two stars collided.

“One possibility is that X7’s gas and dust were ejected at the moment when two stars merged,” Ciurlo said. “In this process, the merged star is hidden inside a shell of dust and gas, which might fit the description of the G objects. And the ejected gas perhaps produced X7-like objects.”

The merger of two stars is very common, especially when they are near black holes, Ciurlo said.

“This is a very messy process: The stars circle each other, get closer, merge, and the new star is hidden within a cloud of dust and gas,” she said. “X7 could be the dust and gas ejected from a merged star that’s still out there somewhere.”

The findings are the first estimate of X7’s mildly elliptical orbit and the most robust analysis to date of the remarkable changes to its appearance, shape and behavior. The research team will continue to use the Keck Observatory to monitor X7’s dramatic changes as the power of the black hole’s gravity yanks it apart.

“It’s a privilege to be able to study the extreme environment at the center of our galaxy,” Campbell said in the statement. “This study can only be done using Keck’s superb capabilities, and performed at the very special and revered Maunakea, with honor and respect to the mauna.”

ALMA confirmation of an obscured hyperluminous radio-loud AGN at z = 6.853 associated with a dusty starburst in the 1.5 deg2 COSMOS field

by Ryan Endsley, Daniel P Stark, Jianwei Lyu, Feige Wang, Jinyi Yang, Xiaohui Fan, Renske Smit, Rychard Bouwens, Kevin Hainline, Sander Schouws in Monthly Notices of the Royal Astronomical Society

Astronomers from the University of Texas and the University of Arizona have discovered a rapidly growing black hole in one of the most extreme galaxies known in the very early Universe. The discovery of the galaxy and the black hole at its centre provides new clues on the formation of the very first supermassive black holes.

Using observations taken with the Atacama Large Millimeter Array (ALMA), a radio observatory sited in Chile, the team have determined that the galaxy, named COS-87259, containing this new supermassive black hole is very extreme, forming stars at a rate 1000 times that of our own Milky Way and containing over a billion solar masses worth of interstellar dust. The galaxy shines bright from both this intense burst of star formation and the growing supermassive black hole at its centre.

The black hole is considered to be a new type of primordial black hole — one heavily enshrouded by cosmic “dust,” causing nearly all of its light to be emitted in the mid-infrared range of the electromagnetic spectrum. The researchers have also found that this growing supermassive black hole (frequently referred to as an active galactic nucleus) is generating a strong jet of material moving at near light speed through the host galaxy.

(a) ALMA [C ii]158 μ m spectrum of COS-87259 (after continuum subtraction) extracted within the 3σ contours of the moment-0 map. The spectrum is binned to half the original resolution for clarity and the red line shows the Gaussian fit. (b) ALMA [C ii] (blue), 158 μ m dust continuum (red), and VLA 3 GHz (green) 2σ, 3σ, and 4σ contour maps of COS-87259 overlaid on the stacked rest-UV image.

Today, black holes with masses millions to billions of times greater than that of our own Sun sit at the centre of nearly every galaxy. How these supermassive black holes first formed remains a mystery for scientists, particularly because several of these objects have been found when the Universe was very young. Because the light from these sources takes so long to reach us, we see them as they existed in the past; in this case, just 750 million years after the Big Bang, which is approximately 5% of the current age of the Universe.

What is particularly astonishing about this new object is that it was identified over a relatively small patch of the sky typically used to detect similar objects — less than 10 times the size of the full moon — suggesting there could be thousands of similar sources in the very early Universe. This was completely unexpected from previous data.

The only other class of supermassive black holes we knew about in the very early Universe are quasars, which are active black holes that are relatively unobscured by cosmic dust. These quasars are extremely rare at distances similar to COS-87259, with only a few tens located over the full sky. The surprising discovery of COS-87259 and its black hole raises several questions about the abundance of very early supermassive black holes, as well as the types of galaxies in which they typically form.

Ryan Endsley, the lead author of the paper and now a Postdoctoral Fellow at The University of Texas at Austin, says “These results suggest that very early supermassive black holes were often heavily obscured by dust, perhaps as a consequence of the intense star formation activity in their host galaxies. This is something others have been predicting for a few years now, and it’s really nice to see the first direct observational evidence supporting this scenario.”

Similar types of objects have been found in the more local, present-day Universe, such as Arp 299 shown here. In this system, two galaxies are crashing together generating an intense starburst as well as heavy obscuration of the growing supermassive black hole in one of the two galaxies.

Endsley adds, “While nobody expected to find this kind of object in the very early Universe, its discovery takes a step towards building a much better understanding of how billion solar mass black holes were able to form so early on in the lifetime of the Universe, as well how the most massive galaxies first evolved.”

Particle entrainment and rotating convection in Enceladus’ ocean

by Ashley M. Schoenfeld, Emily K. Hawkins, Krista M. Soderlund, Steven D. Vance, Erin Leonard, An Yin in Communications Earth & Environment

Although it is relatively small, Enceladus — the sixth largest of Saturn’s 83 moons — has been considered by astronomers to be one of the more compelling bodies in our solar system.

Enceladus stands apart from other celestial bodies because of both its appearance and its behavior. It has the whitest and most reflective surface that astronomers have yet observed. And it’s known for spraying out tiny icy silica particles — so many of them that the particles are an important component of the second outermost ring around Saturn, its so-called E ring.

Enceladus is characterized as an “ocean world,” a celestial body with a substantial volume of liquid water. But unlike oceans on Earth, which are on the planet’s surface, Enceladus’ ocean is protected beneath a thick layer of ice. The ice doesn’t trap the ocean completely, though: Some materials from the watery expanse are released near Enceladus’ warmer south pole from large fractures in the ice known as ‘’tiger stripes.” The silica particles that Enceladus ejects begin their journey at the sea floor, far beneath the moon’s surface — and to date, scientists have not known how that happens or how long the process takes.

Rotationally dominated convection columns.

A new study led by UCLA scientists offers some answers. The research shows that tidal heating in Enceladus’ rocky core creates currents that transport the silica, which is likely released by deep-sea hydrothermal vents over the course of just a few months. Ashley Schoenfeld, a UCLA doctoral student in planetary science, led a group that analyzed data about Enceladus’ orbit, ocean and geology that had been collected by NASA’s Cassini spacecraft. The scientists constructed a theoretical model that could account for the silica’s transport across the ocean.

Enceladus’ active geology is fueled by tidal forces as it orbits Saturn — the moon is tugged and squished by gravity. That deformation creates friction in both the moon’s ice shell and its deep rocky core, The new model demonstrated that the friction heats the bottom of the ocean enough to create a current that transports the silica particles toward the surface.

“Our research shows that these flows are strong enough to pick up materials from the seafloor and bring them to the ice shell that separates the ocean from the vacuum of space,” Schoenfeld said. “The tiger-stripe fractures that cut through the ice shell into this subsurface ocean can act as direct conduits for captured materials to be flung into space. Enceladus is giving us free samples of what’s hidden deep below.”

Particle entrainment in Enceladus’ ocean.

Cassini found substantial amounts of hydrogen gas in the plumes which, together with the silica, present compelling evidence for hydrothermal activity at the ocean floor. The theoretical model devised by the UCLA-led team strengthens that hypothesis by demonstrating a plausible timeframe for the process, and a convincing mechanism that would explain why the plumes contain silica. The model also would help explain why other materials are transported to the surface, along with the silica particles.

“Our model provides further support to the idea that convective turbulence in the ocean efficiently transports vital nutrients from the seafloor to ice shell,” said second author Emily Hawkins, a UCLA alumna who is now an assistant professor of physics at Loyola Marymount University.

On Earth, similar deep-sea hydrothermal vents harbor a multitude of fascinating organisms that feast on minerals the vents release. In the future, spacecraft could gather more data to enable scientists to further study the physical and chemical properties of Enceladus’ potential hydrothermal vent systems. To determine whether those vents could support life, scientists would need to test the plumes for chemical traces of biological activity, known as biosignatures; the new study offers some guidance that should aid the search for those biosignatures.