ST/ Explosion of a red supergiant

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Paradigm

37 min readJan 12, 2022

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Space biweekly vol.43, 29th December — 12th January

TL;DR

Astronomers previously believed that red supergiant stars fell dormant at the end of their lives. A new study shows that red supergiant stars can violently erupt before collapsing into supernovae.
An international research team has discovered a sub-Neptune exoplanet orbiting a red dwarf star.
Astronomers have identified a potential clue to how the universe became reionized after the Big Bang. The researchers identified a black hole, a million times as bright as our sun, that may have been similar to the sources that powered the universe’s reionization.
Images from NASA’s June Spacecraft have given oceanographers the raw materials for a new study that describes the rich turbulence at Jupiter’s poles and the physical forces that drive the large cyclones.
Before the solar system had planets, the sun had rings — bands of dust and gas similar to Saturn’s rings — that likely played a role in Earth’s formation, according to a new study.
Black holes really are giant fuzzballs, a new study says. The study attempts to put to rest the debate over Stephen Hawking’s information paradox, the problem created by Hawking’s conclusion that any data that enters a black hole can never leave. This conclusion accorded with the laws of thermodynamics, but opposed the fundamental laws of quantum mechanics.
The long-term risks of living in space include bone loss, cosmic radiation and muscle weakness, so leaving gravity behind certainly has its obstacles. Some of these potential hurdles have already been studied extensively or are currently being investigated, but researchers have found an important but underserved area of space to study: the brain and gravity’s effect on eyesight.
The secret to producing large batches of stem cells more efficiently may lie in the near-zero gravity conditions of space. Scientists have found that microgravity has the potential to contribute to life-saving advances on Earth by facilitating the rapid mass production of stem cells.
Why the sun’s corona reaches temperatures of several million degrees Celsius is one of the great mysteries of solar physics. A ‘hot’ trail to explain this effect leads to a region of the solar atmosphere just below the corona, where sound waves and certain plasma waves travel at the same speed. In an experiment using the molten alkali metal rubidium and pulsed high magnetic fields, researchers have developed a laboratory model and experimentally confirmed the theoretically predicted behavior of these plasma waves.
Scientists contemplate launching tiny lifeforms into interstellar space.
Upcoming industry events. And more!

Space industry in numbers

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

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

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

Space industry news

Latest research

Final Moments. I. Precursor Emission, Envelope Inflation, and Enhanced Mass Loss Preceding the Luminous Type II Supernova 2020tlf

by W. V. Jacobson-Galán et al. in The Astrophysical Journal

For the first time ever, astronomers have imaged in real time the dramatic end to a red supergiant’s life — watching the massive star’s rapid self-destruction and final death throes before collapsing into a type II supernova.

Led by researchers at Northwestern University and the University of California, Berkeley (UC Berkeley), the team observed the red supergiant during its last 130 days leading up to its deadly detonation.

PS1/YSE g-band explosion image of Type II SN 2020tlf in host galaxy NGC 5731.

The discovery defies previous ideas of how red supergiant stars evolve right before exploding. Earlier observations showed that red supergiants were relatively quiescent before their deaths — with no evidence of violent eruptions or luminous emissions. The new observations, however, detected bright radiation from a red supergiant in the final year before exploding. This suggests at least some of these stars must undergo significant changes in their internal structure, which then result in the tumultuous ejection of gas moments before they collapse.

“This is a breakthrough in our understanding of what massive stars do moments before they die,” said Wynn Jacobson-Galán, the study’s lead author. “Direct detection of pre-supernova activity in a red supergiant star has never been observed before in an ordinary type II supernova. For the first time, we watched a red supergiant star explode.”

Although the work was conducted at Northwestern, where Jacobson-Galán was a National Science Foundation (NSF) Graduate Research Fellow, he has since moved to UC Berkeley. Northwestern co-authors include Deanne Coppejans, Charlie Kilpatrick, Giacomo Terreran, Peter Blanchard and Lindsay DeMarchi, who are all members of Northwestern’s Center for Interdisciplinary and Exploratory Research in Astrophysics (CIERA).

Pre-explosion PS1/YSE stacked griz-band template (top), detection (middle), and difference (bottom) images of progenitor precursor emission preceding SN 2020tlf. Stacked images were created from 13 z-band, 45 i-band, 23 r-band, and 22 g-band pre-explosion observations spanning a phase range of δ t = −169.7 to −3.7 days since first light (MJD 58929–59095). The PS1 g band is not detected.

The University of Hawaii Institute for AstronomyPan-STARRS on Haleakala, Maui, first detected the doomed massive star in summer 2020 via the huge amount of light radiating from the red supergiant. A few months later, in fall of 2020, a supernova lit the sky.

The team quickly captured the powerful flash and obtained the very first spectrum of the energetic explosion, named supernova 2020tlf (SN 2020tlf) using the W.M. Keck Observatory’s Low Resolution Imaging Spectrometer on Maunakea, Hawaii. The data showed direct evidence of dense circumstellar material surrounding the star at the time of explosion, likely the same gas that Pan-STARRS had imaged the red supergiant star violently ejecting earlier in the summer.

“It’s like watching a ticking time bomb,” said Raffaella Margutti, an adjunct associate professor at CIERA and the paper’s senior author. “We’ve never confirmed such violent activity in a dying red supergiant star where we see it produce such a luminous emission, then collapse and combust, until now.”

The team continued to monitor SN 2020tlf after the explosion. Based on data obtained from Keck Observatory’s Deep Imaging and Multi-Object Spectrograph and Near Infrared Echellette Spectrograph, the researchers determined SN 2020tlf’s progenitor red supergiant star — located in the NGC 5731 galaxy about 120 million light-years away from Earth — was 10 times more massive than the sun.

Visual representation of SN 2020tlf’s progenitor system at the time of explosion. Here, the SN shock breaks out from an extended H-rich envelope of a 10–12 M⊙ RSG progenitor star and collides with dense CSM (r ∼1015 cm, vw ≈ 50–200 km s−1), inducing photoionized spectral lines observed in the earliest SN spectrum (shown in blue). Precursor emission was detected for ∼130 days prior to explosion (shown in red) due to the ejection of stellar material. For slower wind velocities (v −w ≲ 50 km s−1), the outer CSM (cyan circle) represents the material ejected prior to the precursor ejection of the inner CSM (dark blue circle). However, material driven off in the pre-SN activity could be the same material as is visible in the photoionization spectrum for wind velocities of vw ≈ 50–200 km s−1.

Margutti and Jacobson-Galán conducted most of the study during their time at Northwestern, with Margutti serving as an associate professor of physics and astronomy and member of CIERA, and Jacobson-Galán as a graduate student in Margutti’s research group. Margutti is now an associate professor of astronomy and astrophysics at UC Berkeley. Northwestern’s remote access to Keck Observatory’s telescopes was integral to their research. From the University’s Evanston campus, astronomers can connect with an on-site telescope operator in Hawaii and choose where to position the telescope. By bypassing long-distance travel to Hawaii, astronomers save precious observing time — often catching transient events like supernovas, which can quickly flare up and then swiftly vanish.

“This significant discovery of a red supergiant supernova is yet one more strong indication of the importance of Northwestern’s investment in access to top private telescope facilities, including the Keck Observatory,” said Vicky Kalogera, the Daniel I. Linzer Distinguished University Professor of Physics and Astronomy at Northwestern’s Weinberg College of Arts and Sciences and director of CIERA. “The Keck telescopes, currently the best on our planet, uniquely enable scientific advances of this caliber as CIERA researchers have shown since our Keck partnership started just a few years ago.”

Margutti, Jacobson-Galán and their Northwestern co-authors are members of the Young Supernova Experiment, which uses the Pan-STARRS telescope to catch supernovae right after they explode.

“I am most excited by all of the new ‘unknowns’ that have been unlocked by this discovery,” Jacobson-Galán said. “Detecting more events like SN 2020tlf will dramatically impact how we define the final months of stellar evolution, uniting observers and theorists in the quest to solve the mystery on how massive stars spend the final moments of their lives.”

TOI-2257 b: A highly eccentric long-period sub-Neptune transiting a nearby M dwarf

by N. Schanche, F. J. Pozuelos, M. N. Günther, R. D. Wells, A. J. Burgasser, et al in Astronomy & Astrophysics

Led by the University of Bern, an international research team has discovered a sub-Neptune exoplanet orbiting a red dwarf star. The discovery was also made thanks to observations performed by the SAINT-EX observatory in Mexico. SAINT-EX is run by a consortium including the Center for Space and Habitability (CSH) at the University of Bern and the National Center of Competence in Research NCCR PlanetS.

“Red dwarfs” are small stars and thus much cooler than our Sun. Around stars like these, liquid water is possible on planets much closer to the star than in our solar system. The distance between an exoplanet and its star is a crucial factor in its detection: the closer a planet is to its host star, the higher the probability that it can be detected.

In a study, researchers led by Dr. Nicole Schanche of the Center for Space and Habitability CSH of the University of Bern report the discovery of the exoplanet TOI-2257 b orbiting a nearby red dwarf. Nicole Schanche is also a member of the National Center of Competence in Research PlanetS, which the University of Bern runs together with the University of Geneva.

TESS target pixel files of Sectors 14, 20, 21, and 26 that observed TOI-2257, generated by means of tpfplotter . The apertures used to extract the photometry by the SPOC pipeline are shown as red shaded regions. The *Gaia* DR2 catalog is over-plotted, with all sources of up to 6 magnitudes in contrast with TOI-2257 shown as red circles. We note that the symbol size scales with the magnitude contrast. While the star is relatively isolated, there is a small amount of contamination from outside sources, ranging from 2–5% of the total flux.

Exoplanets that are very far from our solar system cannot be observed directly with a telescope — they are too small and reflect too little light. However, one way to detect such planets is the transit method. This involves using telescopes to look for dips in the star’s brightness that occur when planets pass in front of the star. Repeated observations of the dips in the star’s brightness give precise measurements of the planet’s orbital period around the star, and the depth of the transit allows researchers to determine the planet’s diameter. When combined with planet mass estimates from other methods, such as using radial velocity measurements, the planet density can be calculated.

Planet TOI-2257 b was initially identified by data from NASA’s Transiting Exoplanet Survey Satellite TESS space telescope. The small star was observed for a total of four months, but the gaps between observations meant that it was not clear whether the decrease in brightness could be explained by the transit of a planet with an orbit of 176, 88, 59, 44 or 35 days.

Observation of the star with the Las Cumbres Observatory Global Telescope subsequently ruled out the possibility that a planet with a 59-day orbital period was causing the drop in brightness. “Next, we wanted to find out if the 35-day orbital period could be possible,” explains Nicole Schanche.

The Mexico-based SAINT-EX telescope, co-operated by the CSH and the NCCR PlanetS, is purpose-built to study red dwarfs and their planets in more detail. SAINT-EX is an acronym that stands for Search And characterIsatioN of Transiting EXoplanets. The project was named in honor of Antoine de Saint-Exupéry (Saint-Ex), the famous writer, poet and aviator. SAINT-EX observed a partial transit of TOI-2257 b and was able to confirm the exoplanet’s exact orbital period around its star, 35 days. “Another 35 days later, SAINT-EX was able to observe the entire transit, which gave us even more information about the properties of the system,” says co-author Robert Wells from the CSH, who was involved in the data processing.

Phase coverage for SAINT-EX and Artemis data. *Top*: evolution of the phase coverage of a hypothetical planet orbiting TOI-2257 as a function of the period, derived from SAINT-EX and Artemis observations (blue dots). The effective phase coverage is the integral of the phase coverage over the 0.1–15 day period range and is equal to 59%. The dotted red (purple) line indicates the period above which the phase coverage is always inferior to 80% (40%), which corresponds to the period of 3.78 days (8.71 days). We note that periods equal to an integer number of days are significantly less covered due to day-night cycles in ground-based observations. *Bottom*: graphical visualization of the coverage of TOI-2257 with SNO and SAINT-EX for a hypothetical planet with orbital periods of 3.78 and 8.71 days, respectively. Each blue circular arc represents one night of observation; its size is proportional to the number of hours observed each night, and a full circle depicts a duration of 3.78 (8.71) days.

With its 35-day orbital period, TOI-2257 b orbits the host star at a distance where liquid water is possible on the planet, and therefore conditions favorable for the emergence of life could exist. Planets in this so-called “habitable zone” near a small red dwarf star are easier to study because they have shorter orbital periods and can therefore be observed more often. The radius of TOI-2257 b (2.2 times larger than Earth’s) suggests that the planet is rather gaseous, with high atmospheric pressure not conducive to life.

“We found that TOI-2257 b does not have a circular, concentric orbit,” explains Nicole Schanche. In fact, it is the most eccentric planet orbiting a cool star ever discovered. “In terms of potential habitability, this is bad news,” Nicole Schanche continues. “While the planet’s average temperature is comfortable, it varies from -80°C to about 100°C depending on where in its orbit the planet is, far from or close to the star.”

A possible explanation for this surprising orbit is that further out in the system a giant planet is lurking and disturbing the orbit of TOI 2257 b. Further observations measuring the radial velocity of the star will help confirm the eccentricity and search for possible additional planets that could not be observed in transit.

The James Webb Space Telescope (JWST), which successfully launched on December 25, will revolutionize research into exoplanet atmospheres. In order to prioritize good candidates for observations with the JWST, a transmission spectroscopy metric (TSM) was developed that rates different system properties. TOI-2257 b is well positioned with respect to TSM and is one of the most attractive sub-Neptune targets for further observations. “In particular, the planet could be studied for signs of features such as water vapor in the atmosphere,” Nicole Schanche concludes.

Moist convection drives an upscale energy transfer at Jovian high latitudes

by Siegelman, L., Klein, P., Ingersoll, A.P. et al. in Nature Physics

Hurtling around Jupiter and its 79 moons is the Juno spacecraft, a NASA-funded satellite that sends images from the largest planet in our solar system back to researchers on Earth. These photographs have given oceanographers the raw materials for a new study that describes the rich turbulence at Jupiter’s poles and the physical forces that drive the large cyclones.

Lead author Lia Siegelman, a physical oceanographer and postdoctoral scholar at Scripps Institution of Oceanography at the University of California San Diego, decided to pursue the research after noticing that the cyclones at Jupiter’s pole seem to share similarities with ocean vortices she studied during her time as a PhD student. Using an array of these images and principles used in geophysical fluid dynamics, Siegelman and colleagues provided evidence for a longtime hypothesis that moist convection — when hotter, less dense air rises — drives these cyclones.

**Infrared image of the northern polar region as seen by JIRAM**1 on 2 February 2017.

“When I saw the richness of the turbulence around the Jovian cyclones with all the filaments and smaller eddies, it reminded me of the turbulence you see in the ocean around eddies,” said Siegelman. “These are especially evident on high-resolution satellite images of plankton blooms for example.”

Siegelman says that understanding Jupiter’s energy system, a scale much larger than Earth’s one, could also help us understand the physical mechanisms at play on our own planet by highlighting some energy routes that could also exist on Earth.

“To be able to study a planet that is so far away and find physics that apply there is fascinating,” she said. “It begs the question, do these processes also hold true for our own blue dot?”

Juno is the first spacecraft to capture images of Jupiter’s poles; previous satellites orbited the equatorial region of the planet, providing views of the planet’s famed Red Spot. Juno is equipped with two camera systems, one for visible light images and another that captures heat signatures using the Jovian Infrared Auroral Mapper (JIRAM), an instrument on the Juno spacecraft supported by the Italian Space Agency.

Siegelman and colleagues analyzed an array of infrared images capturing Jupiter’s north polar region, and in particular the polar vortex cluster. From the images, the researchers could calculate wind speed and direction by tracking the movement of the clouds between images. Next, the team interpreted infrared images in terms of cloud thickness. Hot regions correspond to thin clouds, where it is possible to see deeper into Jupiter’s atmosphere. Cold regions represent thick cloud cover, blanketing Jupiter’s atmosphere.

These findings gave the researchers clues on the energy of the system. Since Jovian clouds are formed when hotter, less dense air rises, the researchers found that the rapidly rising air within clouds acts as an energy source that feeds larger scales up to the large circumpolar and polar cyclones.

Juno first arrived at the Jovian system in 2016, providing scientists with the first look at these large polar cyclones, which have a radius of about 1,000 kilometers or 620 miles. There are eight of these cyclones occurring at Jupiter’s north pole, and five at its south pole. These storms have been present since that first view five years ago. Researchers are unsure how they originated or for how long they have been circulating, but they now know that moist convection is what sustains them. Researchers first hypothesized this energy transfer after observing lightning in storms on Jupiter.

Juno will continue orbiting Jupiter until 2025, providing researchers and the public alike with novel images of the planet and its extensive lunar system.

Rapid turn-on of a luminous X-ray source in the candidate Lyman continuum emitting galaxy Tol 0440–381

by P Kaaret, J Bluem, A H Prestwich in Monthly Notices of the Royal Astronomical Society: Letters

About 400,000 years after the universe was created began a period called “The Epoch of Reionization.” During this time, the once hotter universe began to cool and matter clumped together, forming the first stars and galaxies. As these stars and galaxies emerged, their energy heated the surrounding environment, reionizing some of the remaining hydrogen in the universe.

The universe’s reionization is well known, but determining how it happened has been tricky. To learn more, astronomers have peered beyond our Milky Way galaxy for clues. In a new study, astronomers at the University of Iowa identified a source in a suite of galaxies called Lyman continuum galaxies that may hold clues about how the universe was reionized.

In the study, the Iowa astronomers identified a black hole, a million times as bright as our sun, that may have been similar to the sources that powered the universe’s reionization. That black hole, the astronomers report from observations made in February 2021 with NASA’s flagship Chandra X-ray observatory, is powerful enough to punch channels in its respective galaxy, allowing ultraviolet photons to escape and be observed.

“The implication is that outflows from black holes may be important to enable escape of the ultraviolet radiation from galaxies that reionized the intergalactic medium,” says Phil Kaaret, professor and chair in the Department of Physics and Astronomy and the study’s corresponding author.
“We can’t yet see the sources that actually powered the universe’s reionization because they are too far away,” Kaaret says. “We looked at a nearby galaxy with properties similar to the galaxies that formed in the early universe. One of the primary reasons that the James Webb Space Telescope was built was to try to see the galaxies hosting the sources that actually powered the universe’s reionization.”

Planetesimal rings as the cause of the Solar System’s planetary architecture

by Andre Izidoro, Rajdeep Dasgupta, Sean N. Raymond, Rogerio Deienno, Bertram Bitsch, Andrea Isella in Nature Astronomy

Before the solar system had planets, the sun had rings — bands of dust and gas similar to Saturn’s rings — that likely played a role in Earth’s formation, according to a new study.

“In the solar system, something happened to prevent the Earth from growing to become a much larger type of terrestrial planet called a super-Earth,” said Rice University astrophysicist André Izidoro, referring to the massive rocky planets seen around at least 30% of sun-like stars in our galaxy.

Izidoro and colleagues used a supercomputer to simulate the solar system’s formation hundreds of times. Their model produced rings like those seen around many distant, young stars. It also faithfully reproduced several features of the solar system missed by many previous models, including:

An asteroid belt between Mars and Jupiter containing objects from both the inner and outer solar system.
The locations and stable, almost circular orbits of Earth, Mars, Venus and Mercury.
The masses of the inner planets, including Mars, which many solar system models overestimate.
The dichotomy between the chemical makeup of objects in the inner and outer solar system.
A Kuiper belt region of comets, asteroids and small bodies beyond the orbit of Neptune.

An illustration of three distinct, planetesimal-forming rings that could have produced the planets and other features of the solar system, according to a computational model from Rice University. The vaporization of solid silicates, water and carbon monoxide at “sublimation lines” (top) caused “pressure bumps” in the sun’s protoplanetary disk, trapping dust in three distinct rings. As the sun cooled, pressure bumps migrated sunward allowing trapped dust to accumulate into asteroid-sized planetesimals. The chemical composition of objects from the inner ring (NC) differs from the composition of middle- and outer-ring objects (CC). Inner-ring planetesimals produced the inner solar system’s planets (bottom), and planetesimals from the middle and outer rings produced the outer solar system planets and Kuiper Belt (not shown). The asteroid belt formed (top middle) from NC objects contributed by the inner ring (red arrows) and CC objects from the middle ring (white arrows). (Image courtesy of Rajdeep Dasgupta)

The study by astronomers, astrophysicists and planetary scientists from Rice, the University of Bordeaux, Southwest Research Institute in Boulder, Colorado, and the Max Planck Institute for Astronomy in Heidelberg, Germany, draws on the latest astronomical research on infant star systems.

Their model assumes three bands of high pressure arose within the young sun’s disk of gas and dust. Such “pressure bumps” have been observed in ringed stellar disks around distant stars, and the study explains how pressure bumps and rings could account for the solar system’s architecture, said lead author Izidoro, a Rice postdoctoral researchers who received his Ph.D. training at Sao Paulo State University in Brazil.

“If super-Earths are super-common, why don’t we have one in the solar system?” Izidoro said. “We propose that pressure bumps produced disconnected reservoirs of disk material in the inner and outer solar system and regulated how much material was available to grow planets in the inner solar system.”

**Final distribution of planetesimals in a simulation with three pressure bumps.**

For decades, scientists believed gas and dust in protoplanetary disks gradually became less dense, dropping smoothly as a function of distance from the star. But computer simulations show planets are unlikely to form in smooth-disk scenarios.

“In a smooth disk, all solid particles — dust grains or boulders — should be drawn inward very quickly and lost in the star,” said astronomer and study co-author Andrea Isella, an associate professor of physics and astronomy at Rice. “One needs something to stop them in order to give them time to grow into planets.”

When particles move faster than the gas around them, they “feel a headwind and drift very quickly toward the star,” Izidoro explained. At pressure bumps, gas pressure increases, gas molecules move faster and solid particles stop feeling the headwind. “That’s what allows dust particles to accumulate at pressure bumps,” he said. Isella said astronomers have observed pressure bumps and protoplanetary disk rings with the Atacama Large Millimeter/submillimeter Array, or ALMA, an enormous 66-dish radio telescope that came online in Chile in 2013.

“ALMA is capable of taking very sharp images of young planetary systems that are still forming, and we have discovered that a lot of the protoplanetary disks in these systems are characterized by rings,” Isella said. “The effect of the pressure bump is that it collects dust particles, and that’s why we see rings. These rings are regions where you have more dust particles than in the gaps between rings.”

The model by Izidoro and colleagues assumed pressure bumps formed in the early solar system at three places where sunward-falling particles would have released large amounts of vaporized gas.

“It’s just a function of distance from the star, because temperature is going up as you get closer to the star,” said geochemist and study co-author Rajdeep Dasgupta, the Maurice Ewing Professor of Earth Systems Science at Rice. “The point where the temperature is high enough for ice to be vaporized, for example, is a sublimation line we call the snow line.”

In the Rice simulations, pressure bumps at the sublimation lines of silicate, water and carbon monoxide produced three distinct rings. At the silicate line, the basic ingredient of sand and glass, silicon dioxide, became vapor. This produced the sun’s nearest ring, where Mercury, Venus, Earth and Mars would later form. The middle ring appeared at the snow line and the farthest ring at the carbon monoxide line.

**Cumulative mass fraction distributions representing the feeding zones of terrestrial planets in simulations with Jupiter and Saturn in their current orbits.**

Protoplanetary disks cool with age, so sublimation lines would have migrated toward the sun. The study showed this process could allow dust to accumulate into asteroid-sized objects called planetesimals, which could then come together to form planets. Izidoro said previous studies assumed planetesimals could form if dust were sufficiently concentrated, but no model offered a convincing theoretical explanation of how dust might accumulate.

“Our model shows pressure bumps can concentrate dust, and moving pressure bumps can act as planetesimal factories,” Izidoro said. “We simulate planet formation starting with grains of dust and covering many different stages, from small millimeter-sized grains to planetesimals and then planets.”

Many previous solar system simulations produced versions of Mars as much as 10 times more massive than Earth. The model correctly predicts Mars having about 10% of Earth’s mass because “Mars was born in a low-mass region of the disk,” Izidoro said.

Dasgupta said the model also provides a compelling explanation for two of the solar system’s cosmochemical mysteries: the marked difference between the chemical compositions of inner- and outer-solar system objects, and the presence of each of those objects in the asteroid belt between Mars and Jupiter. Izidoro’s simulations showed the middle ring could account for the chemical dichotomy by preventing outer-system material from entering the inner system. The simulations also produced the asteroid belt in its correct location, and showed it was fed objects from both the inner and outer regions.

“The most common type of meteorites we get from the asteroid belt are isotopically similar to Mars,” Dasgupta said. “Andre explains why Mars and these ordinary meteorites should have a similar composition. He’s provided a nuanced answer to this question.”

Contrasting the fuzzball and wormhole paradigms for black holes

by Bin Guo, Marcel R. R. Hughes, Samir D. Mathur, Madhur Mehta in Turkish Journal of Physics

Black holes really are giant fuzzballs, a new study says. The study attempts to put to rest the debate over Stephen Hawking’s famous information paradox, the problem created by Hawking’s conclusion that any data that enters a black hole can never leave. This conclusion accorded with the laws of thermodynamics, but opposed the fundamental laws of quantum mechanics.

“What we found from string theory is that all the mass of a black hole is not getting sucked in to the center,” said Samir Mathur, lead author of the study and professor of physics at The Ohio State University. “The black hole tries to squeeze things to a point, but then the particles get stretched into these strings, and the strings start to stretch and expand and it becomes this fuzzball that expands to fill up the entirety of the black hole.”

The study found that string theory almost certainly holds the answer to Hawking’s paradox, as the paper’s authors had originally believed. The physicists proved theorems to show that the fuzzball theory remains the most likely solution for Hawking’s information paradox. Mathur published a study in 2004 that theorized black holes were similar to very large, very messy balls of yarn — “fuzzballs” that become larger and messier as new objects get sucked in.

Radiation of different regions near spatial infinity separated by very long distances. The arrow shows the interfering such experiments.

“The bigger the black hole, the more energy that goes in, and the bigger the fuzzball becomes,” Mathur said. The 2004 study found that string theory, the physics theory that holds that all particles in the universe are made of tiny vibrating strings, could be the solution to Hawking’s paradox. With this fuzzball structure, the hole radiates like any normal body, and there is no puzzle. After Mathur’s 2004 study and other, similar works, “many people thought the problem was solved,” he said. “But in fact, a section of people in the string theory community itself thought they would look for a different solution to Hawking’s information paradox. They were bothered that, in physical terms, the whole structure of the black hole had changed.”

Studies in recent years attempted to reconcile Hawking’s conclusions with the old picture of the hole, where one can think of the black hole as being “empty space with all its mass in the center.” One theory, the wormhole paradigm, suggested that black holes might be one end of a bridge in the space-time continuum, meaning anything that entered a black hole might appear on the other end of the bridge — the other end of the wormhole — in a different place in space and time. In order for the wormhole picture to work, though, some low-energy radiation would have to escape from the black hole at its edges.

This recent study proved a theorem — the “effective small corrections theorem” — to show that if that were to happen, black holes would not appear to radiate in the way that they do. The researchers also examined physical properties from black holes, including topology change in quantum gravity, to determine whether the wormhole paradigm would work.

“In each of the versions that have been proposed for the wormhole approach, we found that the physics was not consistent,” Mathur said. “The wormhole paradigm tries to argue that, in some way, you could still think of the black hole as being effectively empty with all the mass in the center. And the theorems we prove show that such a picture of the hole is not a possibility.”

Comparison of Dural Venous Sinus Volumes Before and After Flight in Astronauts With and Without Spaceflight-Associated Neuro-Ocular Syndrome

by Mark J. Rosenberg, Michael A. Coker, James A. Taylor, Milad Yazdani, M. Gisele Matheus, Christopher K. Blouin, Sami Al Kasab, Heather R. Collins, Donna R. Roberts in JAMA Network Open

Colonizing Mars is no longer solely the work of science fiction but a potential future option for people who desire to live among the weightless. For headline grabbers like Jeff Bezos, NASA and Elon Musk, space colonization — or space settlement, a preferred term recommended by Bill Nye — is a big goal for the 21st century.

The long-term risks of living in space include bone loss, cosmic radiation and muscle weakness, just to name a few, so leaving gravity behind certainly has its obstacles. Some of these potential hurdles have already been studied extensively or are currently being investigated, but researchers at MUSC Health have found an important but underserved area of space to study: the brain and gravity’s effect on eyesight.

In a recent paper, researchers look at Spaceflight-Associated Neuro-Ocular Syndrome (SANS) and compare brain scans before and after spaceflight. The longer astronauts stay in space, the more they’ve reported blurry vision and eyesight problems when they return to earth, according to Mark Rosenberg, M.D., a neurology resident at MUSC Health and a researcher on the paper.

Three-Dimensional Reconstructions of the Preflight and Postflight Venograms for an Astronaut with Spaceflight-Associated Neuro-Ocular Syndrome (SANS) and an Astronaut Without SANS

“It’s gotten to the point where astronauts actually carry extra pairs of glasses when they go into space,” said Rosenberg. “They know that their vision is going to be deteriorating up there, and they’ve even started calling them Space Anticipation Glasses. And, in fact, depending on how you define it, it affects about 70% of astronauts.”

With SANS, astronauts return to earth with altered visual acuity and struggle to distinguish between shapes at a distance. The globes of their eyes flatten, parts of their retinas show injury and their optic disks swell. Some astronauts recover from these changes in a few weeks, while others can take months or even years. There are also some who never fully recover.

Preflight to Postflight Percentage Changes in Venous Sinus Volumes for the Superior Sagittal Sinus and Left and Right Transverse/Sigmoid Sinuses for Astronauts With and Without Spaceflight-Associated Neuro-Ocular Syndrome (SANS)

In addition to preparing for space colonization, Donna Roberts, M.D., an MUSC Health neuro-radiologist and the primary investigator for this research paper, says studies like this one also help doctors learn more about conditions that affect people on earth generally. “We can learn more about the role gravity plays on fluid around the brain, for instance,” she said. “And it gives us insight into how disorders of cerebrospinal fluid circulation affect patients not just in space but also here on earth.”

Roberts and her team found that astronauts with SANS had increased intracranial dural venous volumes compared to their MRI scans taken just before flight. As large veins that take blood from the brain to the heart, the dural venous sinuses serve a vital role in blood circulation and shouldn’t stretch or change. But with SANS, blood volume increases, and the dural venous sinuses enlarge. These findings suggest that there is an association between intracranial venous congestion and the development of SANS.

NASA has deemed SANS one of its highest research priorities, according to Roberts, and the results of this paper move that research forward by providing insight into what happens to the brain and eyesight in space. Much research focuses on muscle loss in space, but rarely does it look at the brain specifically.

“If we’re planning on setting up a colony in space, we’re going to have to understand how gravity affects the entire human body,” Roberts said. “And that includes the brain.”
Rosenberg agrees. “As clinicians, one of the things we do is treat the human body,” he said. “And that’s not just now but in the future as well. So really understanding these conditions as a whole, before they start to affect colonists already on a foreign planet where everything wants to kill them, is probably one of the best ways we can apply this research.”

Next, Roberts and Rosenberg will look at the ways SANS may differ between genders. Without being able to perform an MRI in space, Roberts says it’s difficult to pinpoint when exactly the change in the dural venous sinuses occurs — it could be during flight takeoff, in space or while acclimating to earth upon return — so she is also looking into a mobile MRI machine to perform scans in space to better understand how the condition develops.

“As we head into this new era of human spaceflight, SANS remains one of our biggest problems and obstacles,” Roberts said. “But we are making progress in understanding the condition.”

Mode Conversion and Period Doubling in a Liquid Rubidium Alfvén-Wave Experiment with Coinciding Sound and Alfvén Speeds

by F. Stefani, J. Forbriger, Th. Gundrum, T. Herrmannsdörfer, J. Wosnitza in Physical Review Letters

Why the Sun’s corona reaches temperatures of several million degrees Celsius is one of the great mysteries of solar physics. A “hot” trail to explain this effect leads to a region of the solar atmosphere just below the corona, where sound waves and certain plasma waves travel at the same speed. In an experiment using the molten alkali metal rubidium and pulsed high magnetic fields, a team from the Helmholtz-Zentrum Dresden-Rossendorf (HZDR), a German national lab, has developed a laboratory model and for the first time experimentally confirmed the theoretically predicted behavior of these plasma waves — so-called Alfvén waves.

At 15 million degrees Celsius, the center of our Sun is unimaginably hot. At its surface, it emits its light at a comparatively moderate 6000 degrees Celsius. “It is all the more astonishing that temperatures of several million degrees suddenly prevail again in the overlying Sun’s corona,” says Dr. Frank Stefani. His team conducts research at the HZDR Institute of Fluid Dynamics on the physics of celestial bodies — including our central star. For Stefani, the phenomenon of corona heating remains one of the great mysteries of solar physics, one that keeps running through his mind in the form of a very simple question: “Why is the pot warmer than the stove?”

Experimental setting. (a) Stainless-steel container filled with rubidium. (b) Holder with four pickup coils (PU 1–PU 4) and four compensation coils (CC). (c) Geometrical details of the construction. PP 1–PP 4 denote four electric-potential probes soldered on the container. The three orange triangles indicate the rim contacts (RCs) encircling the bottom part of the container. LC is the lower contact. All sizes are in millimeters. (d) Schematic for the driving of the torsional Alfvén wave in the lower part of the container.

That magnetic fields play a dominant role in heating the Sun’s corona is now widely accepted in solar physics. However, it remains controversial whether this effect is mainly due to a sudden change in magnetic field structures in the solar plasma or to the dampening of different types of waves. The new work of the Dresden team focuses on the so-called Alfvén waves that occur below the corona in the hot plasma of the solar atmosphere, which is permeated by magnetic fields. The magnetic fields acting on the ionized particles of the plasma resemble a guitar string, whose playing triggers a wave motion. Just as the pitch of a strummed string increases with its tension, the frequency and propagation speed of the Alfvén wave increases with the strength of the magnetic field.

“Just below the Sun’s corona lies the so-called magnetic canopy, a layer in which magnetic fields are aligned largely parallel to the solar surface. Here, sound and Alfvén waves have roughly the same speed and can therefore easily morph into each other. We wanted to get to exactly this magic point — where the shock-like transformation of the magnetic energy of the plasma into heat begins,” says Stefani, outlining his team’s goal.

Soon after their prediction in 1942, the Alfvén waves had been detected in first liquid-metal experiments and later studied in detail in elaborate plasma physics facilities. Only the conditions of the magnetic canopy, considered crucial for corona heating, remained inaccessible to experimenters until now. On the one hand, in large plasma experiments the Alfvén speed is typically much higher than the speed of sound. On the other hand, in all liquid-metal experiments to date, it has been significantly lower. The reason for this: the relatively low magnetic field strength of common superconducting coils with constant field of about 20 tesla.

But what about pulsed magnetic fields, such as those that can be generated at the HZDR’s Dresden High Magnetic Field Laboratory (HLD) with maximum values of almost 100 tesla? This corresponds to about two million times the strength of the Earth’s magnetic field: Would these extremely high fields allow Alfvén waves to break through the sound barrier? By looking at the properties of liquid metals, it was known in advance that the alkali metal rubidium actually reaches this magic point already at 54 tesla.

But rubidium ignites spontaneously in air and reacts violently with water. The team therefore initially had doubts as to whether such a dangerous experiment was advisable at all. The doubts were quickly dispelled, recalls Dr. Thomas Herrmannsdörfer of the HLD: “Our energy supply system for operating the pulse magnets converts 50 megajoules in a fraction of a second — with that, we could theoretically get a commercial airliner to take off in a fraction of a second. When I explained to my colleagues that a thousandth of this amount of chemical energy of the liquid rubidium does not worry me very much, their facial expressions visibly brightened.”

**Dependence of various measured signals on the magnetic field.**

Nevertheless, it was still a rocky road to the successful experiment. Because of the pressures of up to fifty times the atmospheric air pressure generated in the pulsed magnetic field, the rubidium melt had to be enclosed in a sturdy stainless steel container, which an experienced chemist, brought out of retirement, was to fill. By injecting alternating current at the bottom of the container while simultaneously exposing it to the magnetic field, it was finally possible to generate Alfvén waves in the melt, whose upward motion was measured at the expected speed.

The novelty: while up to the magic field strength of 54 tesla all measurements were dominated by the frequency of the alternating current signal, exactly at this point a new signal with halved frequency appeared. This sudden period doubling was in perfect agreement with the theoretical predictions. The Alfvén waves of Stefani’s team had broken through the sound barrier for the first time. Although not all observed effects can yet be explained so easily, the work contributes an important detail to solving the puzzle of the Sun’s corona heating. For the future, the researchers are planning detailed numerical analyses and further experiments.

Biomanufacturing in low Earth orbit for regenerative medicine

by Arun Sharma, Rachel A. Clemens, Orquidea Garcia, et al in Stem Cell Reports

The secret to producing large batches of stem cells more efficiently may lie in the near-zero gravity conditions of space. Scientists at Cedars-Sinai have found that microgravity has the potential to contribute to life-saving advances on Earth by facilitating the rapid mass production of stem cells.

A new paper, led by Cedars Sinai, highlights key opportunities discussed during the 2020 Biomanufacturing in Space Symposium to expand the manufacture of stem cells in space.

Biomanufacturing — a type of stem cell production that uses biological materials such as microbes to produce substances and biomaterials suitable for use in preclinical, clinical, and therapeutic applications — can be more productive in microgravity conditions.

Examples of tissue engineering work aboard the ISS

“We are finding that spaceflight and microgravity is a desirable place for biomanufacturing because it confers a number of very special properties to biological tissues and biological processes that can help mass produce cells or other products in a way that you wouldn’t be able to do on Earth,” said stem cell biologist Arun Sharma, PhD, research scientist and head of a new research laboratory in the Cedars-Sinai Board of Governors Regenerative Medicine Institute, Smidt Heart Institute and Department of Biomedical Sciences.
“The last two decades have seen remarkable advances in regenerative medicine and exponential advancement in space technologies enabling new opportunities to access and commercialize space,” he said.

Attendees at the virtual space symposium in December identified more than 50 potential commercial opportunities for conducting biomanufacturing work in space, according to the Cedars-Sinai paper. The most promising fell into three categories: disease modeling, biofabrication, and stem-cell-derived products.

The first, disease modeling, is used by scientists to study diseases and possible treatments by replicating full-function structures — whether using stem cells, organoids (miniature 3D structures grown from human stem cells that resemble human tissue), or other tissues. Investigators have found that once the body is exposed to low-gravity conditions for extended periods of time, it experiences accelerated bone loss and aging. By developing disease models based on this accelerated aging process, research scientists can better understand the mechanisms of the aging process and disease progression.

“Not only can this work help astronauts, but it can also lead to us manufacturing bone constructs or skeletal muscle constructs that could be applied to diseases like osteoporosis and other forms of accelerated bone aging and muscle wasting that people experience on Earth,” said Sharma, who is the corresponding author of the paper.

Another highly discussed topic at the symposium was biofabrication, which uses manufacturing processes to produce materials like tissues and organs. 3D printing is one of the core biofabrication technologies.

Evolution of therapeutic discovery, testing, and translation pathways.

A major issue with producing these materials on Earth involves gravity-induced density, which makes it hard for cells to expand and grow. With the absence of gravity and density in space, scientists are hopeful that they can use 3D printing to print unique shapes and products, like organoids or cardiac tissues, in a way that can’t be replicated on Earth. The third category has to do with the production of stem cells and understanding how some of their fundamental properties are influenced by microgravity. Some of these properties include potency, or the ability of a stem cell to renew itself, and differentiation, the ability for stem cells to turn into other cell types.

Understanding some of the effects of spaceflight on stem cells can potentially lead to better ways to manufacture large numbers of cells in the absence of gravity. Scientists from Cedars-Sinai will be sending stem cells into space early next year, in conjunction with NASA and a private contractor, Space Tango, to test whether it is possible to produce large batches in a low gravity environment.

“While we are still in the exploratory phase of some of this research, this is no longer in the realm of science fiction,” Sharma said. “Within the next five years we may see a scenario where we find cells or tissues that can be made in a way that is simply not possible here on Earth. And I think that’s extremely exciting.”

Interstellar space biology via Project Starlight

by Stephen Lantin, Sophie Mendell, Ghassan Akkad, Alexander N. Cohen, Xander Apicella, Emma McCoy, Eliana Beltran-Pardo, Michael Waltemathe, Prasanna Srinivasan, Pradeep M. Joshi, Joel H. Rothman, Philip Lubin in Acta Astronautica

No longer solely in the realm of science fiction, the possibility of interstellar travel has appeared, tantalizingly, on the horizon. Although we may not see it in our lifetimes — at least not some real version of the fictional warp-speeding, hyperdriving, space-folding sort — we are having early conversations of how life could escape the tether of our solar system, using technology that is within reach.

For UC Santa Barbara professors Philip Lubin and Joel Rothman, it’s a great time to be alive. Born of a generation that saw breathtaking advances in space exploration, they carry the unbridled optimism and creative spark of the early Space Age, when humans first found they could leave the Earth.

“The Apollo moon voyages were among the most momentous events in my life and contemplating them still blows my mind,” said Rothman, a distinguished professor in the Department of Molecular, Cellular and Developmental Biology, and a self-admitted “space geek.”

**Directed Energy Propulsion of a Light Sail.** (a) A light sail and payload propelled into interstellar space by directed energy laser propulsion. Emitted photons from a standoff laser array on the surface of the Earth (space-based laser arrays are also possible) impart momentum on the sail by reflection so as to accelerate the spacecraft up to relativistic speeds. *Artist’s rendition.* (b) The laser array is composed of many small, modular sub-elements which can be articulated, switched off, and added so as to enable a large mission space. As the capability of directed energy propulsion grows, relativistic flight will become possible.

A mere 50 years have passed since that pivotal era, but humanity’s knowledge of space and the technology to explore it have improved immensely, enough for Rothman to join experimental cosmologist Lubin in considering what it would take for living beings to embark on a journey across the vast distance separating us from our nearest neighbor in the galaxy.

“I think it’s our destiny to keep exploring,” Rothman said. “Look at the history of the human species. We explore at smaller and smaller levels down to subatomic levels and we also explore at increasingly larger scales. Such drive toward ceaseless exploration lies at the core of who we are as a species.”

The biggest challenge to human-scale interstellar travel is the enormous distance between Earth and the nearest stars. The Voyager missions have proven that we can send objects across the 12 billion miles it takes to exit the bubble surrounding our solar system, the heliosphere. But the car-sized probes, traveling at speeds of more than 35,000 miles per hour, took 40 years to reach there and their distance from Earth is only a tiny fraction of that to the next star. If they were headed to the closest star, it would take them over 80,000 years to reach it.

That challenge is a major focus of Lubin’s work, in which he reimagines the technology it would take to reach the next solar system in human terms. Traditional onboard chemical propulsion (a.k.a. rocket fuel) is out; it can’t provide enough energy to move the craft fast enough, and the weight of it and current systems needed to propel it are not viable for the relativistic speeds the craft needs to achieve. New propulsion technologies are required — and this is where the UCSB directed energy research program of using light as the “propellant” comes in.

“This has never been done before, to push macroscopic objects at speeds approaching the speed of light,” said Lubin, a professor in the Department of Physics. Mass is such a huge barrier, in fact, that it rules out any human missions for the foreseeable future.

As a result, his team turned to robots and photonics. Small probes with onboard instrumentation that sense, collect and transmit data back to Earth will be propelled up to 20–30% of the speed of light by light itself using a laser array stationed on Earth, or possibly the moon. “We don’t leave home with it,” as Lubin explained, meaning the primary propulsion system stays “at home” while spacecraft are “shot out” at relativistic speeds. The main propulsion laser is turned on for a short period of time and then the next probe is readied to be launched.

“It would probably look like a semiconductor wafer with an edge to protect it from the radiation and dust bombardment as it goes through the interstellar medium,” Lubin said. “It would probably be the size of your hand to start with.” As the program evolves the spacecraft become larger with enhanced capability. The core technology can also be used in a modified mode to propel much larger spacecraft within our solar system at slower speeds, potentially enabling human missions to Mars in as little as one month, stopping included. This is another way of spreading life, but in our solar system.

At these relativistic speeds — roughly 100 million miles per hour — the wafercraft would reach the next solar system, Proxima Centauri, in roughly 20 years. Getting to that level of technology will require continuous innovation and improvement of both the space wafer, as well the photonics, where Lubin sees “exponential growth” in the field. The basic project to develop a roadmap to achieve relativistic flight via directed energy propulsion is supported by NASA and private foundations such as the Starlight program and by the Breakthrough Initiatives as the Starshot program.

“When I learned that the mass of these craft could reach gram levels or larger, it became clear that they could accomodate living animals,” said Rothman, who realized that the creatures he’d been studying for decades, called C. elegans, could be the first Earthlings to travel between the stars. These intensively studied roundworms may be small and plain, but they are experimentally accomplished creatures, Rothman said. “Research on this little animal has led to Nobel prizes to six researchers thus far,” he noted.

C. elegans are already veterans of space travel, as the subject of experiments conducted on the International Space Station and aboard the space shuttle, even surviving the tragic disintegration of the Columbia shuttle. Among their special powers, which they share with other potential interstellar travelers that Rothman studies, tardigrades (or, more affectionately, water bears) can be placed in suspended animation in which virtually all metabolic function is arrested. Thousands of these tiny creatures could be placed on a wafer, put in suspended animation, and flown in that state until reaching the desired destination. They could then be wakened in their tiny StarChip and precisely monitored for any detectable effects of interstellar travel on their biology, with the observations relayed to Earth by photonic communication.

“We can ask how well they remember trained behavior when they’re flying away from their eathly origin at near the speed of light, and examine their metabolism, physiology, neurological function, reproduction and aging,” Rothman added. “Most experiments that can be conducted on these animals in a lab can be performed onboard the StarChips as they whiz through the cosmos.” The effects of such long odysseys on animal biology could allow the scientists to extrapolate to potential effects on humans.
“We could start thinking about the design of interstellar transporters, whatever they may be, in a way that could ameliorate the issues that are detected in these diminutive animals,” Rothman said.

Of course, being able to send humans to interstellar space is great for movies, but in reality is still a far away dream. By the time we get to that point we may have created more suitable life forms or hybrid human-machines that are more resilient.

“This is a generational program,” Lubin said. Scientists of coming generations ideally will contribute to our knowledge of interstellar space and its challenges, and enhance the design of the craft as technology improves. With the primary propulsion system being light, the underlying technology is on an exponential growth curve, much like electronics with a “Moore’s Law” like expanding capability.

Metabolic rate (MR) and mass for various groups of living organisms. Despite the vast diversity of species, we observe a near universal energy requirement per unit mass of tissue. This generalization excludes species capable of cryptobiosis (such as tardigrades, brine shrimp, and *Chironomidae*), which exhibit virtually no metabolic activity while in a state of suspended animation, making them better suited for interstellar flight.

We’re bound to our solar system for the forseeable future; humans are fragile and delicate away from our home planet. But that hasn’t stopped Lubin, Rothman, their research teams and their diverse collaborators, which include a radiation specialist and a science-trained theologian, to contemplate both the physiological and ethical aspects of sending life to space — and perhaps even propagating life in space.

“There are the ethics,” Lubin explained, “of planetary protection,” in which serious thought is given to the possibility of contamination, either from our planet to others or vice versa. “I think if you started talking about directed propagation of life, which is sometimes called panspermia — this idea that life came from elsewhere and ended up on the earth by comets and other debris, or even intentionally from another civilization — the idea that we would purposefully send out life does bring up big questions.”

So far, the authors contend, there is no risk of forward contamination, as the probes nearing any other planet would burn up in their atmosphere or be obliterated in the collision with the surface. Because the wafercraft are on a one-way trip, there’s no risk that any extraterrestrial microbes will return to Earth. While still somewhat on the fringe, the theory of panspermia seems to be getting some serious, if limited, attention, given how easy it is to propagate life when conditions are right and the discovery of several exoplanets and other celestial bodies that may have been, or could be, supportive of life as we know it.

“Some people have mused and published on ideas such as ‘is the universe a lab experiment from some advanced civilization,’” Lubin said. “So people are certainly willing to think about advanced civilizations. Questions are good but answers are better. Right now we simply ponder these questions without the answers yet.”

Another issue currently being contemplated in the wider space exploration community: What are the ethics of sending humans to Mars and other distant places knowing they may never come home? What about sending out small micro-organisms or human DNA? These existential inquiries are as old as the first human migrations and seafaring voyages, the answers to which will likely come the moment we’re ready to take these journeys.