Study Finding: Gravitational Instability in a Planet-forming Disk

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Credit: Peter Schmidt from Pixabay

Nature abstract of the study findings:

The canonical theory for planet formation in circumstellar disks proposes that planets are grown from initially much smaller seeds. The long-considered alternative theory proposes that giant protoplanets can be formed directly from collapsing fragments of vast spiral arms induced by gravitational instability—if the disk is gravitationally unstable. For this to be possible, the disk must be massive compared with the central star: a disk-to-star mass ratio of 1:10 is widely held as the rough threshold for triggering gravitational instability, inciting substantial non-Keplerian dynamics and generating prominent spiral arms. Although estimating disk masses has historically been challenging, the motion of the gas can reveal the presence of gravitational instability through its effect on the disk-velocity structure. Here we present kinematic evidence of gravitational instability in the disk around AB Aurigae, using deep observations of 13CO and C18O line emission with the Atacama Large Millimeter/submillimeter Array (ALMA). The observed kinematic signals strongly resemble predictions from simulations and analytic modelling. From quantitative comparisons, we infer a disk mass of up to a third of the stellar mass enclosed within 1″ to 5″ on the sky.

Citation: Speedie, J., Dong, R., Hall, C. et al. Gravitational instability in a planet-forming disk. Nature 633, 58–62 (2024).
https://doi.org/10.1038/s41586-024-07877-0

Study-related stories:

MIT News

Space Daily

Universe Today

Space Stories: The Search for Super Civilization, Students Sought for Lunar Mission, and Kilonova Seekers

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Image (Credit): Murchison Widefield Array radio telescope in Western Australia. (Curtin University)

Here are some recent stories of interest.

—SETI Institute: “SETI Institute Starts First Low Frequency Search for Alien Technology in Distant Galaxies“

The SETI Institute, the Berkeley SETI Research Center and the International Centre for Radio Astronomy Research announced a groundbreaking study using the Murchison Widefield Array (MWA) in Western Australia. Led by Dr. Chenoa Tremblay of the SETI Institute and Prof. Steven Tingay of Curtin University, this research is the first to search for signs of alien technology in galaxies beyond our own, focusing on low radio frequencies (100 MHz).

This innovative study used the MWA’s large field of view (FOV), allowing the team to cover about 2,800 galaxies in one observation, of which 1300 we know the distance to. Usually, the search for extraterrestrial intelligence (SETI) has focused on signals within our galaxy. This new approach goes further, looking at distant galaxies. This new approach looks at distant galaxies, making it one of the most detailed searches for super civilizations—those more advanced than ours. To send a signal from another galaxy, a civilization would need technology powerful enough to use the energy of their sun or several stars in their galaxy.

—KXAN: “College Students Sought to Help NASA Return to Moon“

NASA needs some help with frozen liquid. As part of the space agency’s planned trip to the moon as part of the Artemis mission, NASA is looking for a way to store “super-chilled” propellants for months on end. They’re asking college students for help. Announced earlier this month, NASA’s 2025 Human Lander Challenge (HuLC) is open for submissions. The competition, now in its second year, is asking for students to develop innovative methods for “in-space cryogenic liquid storage.”

—University of Portsmouth: “Citizen Science Project Identifies 20 New Astronomical Discoveries“

A citizen science project, which invites members of the public to take part in identifying cosmic explosions, has already identified 20 new astronomical discoveries. Over 2,000 volunteers across 105 different countries have worked on 600,000 classifications over a six-month period. The project ‘Kilonova Seekers’ aims to find kilonovae – the cosmic explosions of neutron stars and black holes colliding in distant galaxies. Volunteers are asked to play ‘spot the difference’ using data from the two Gravitational-wave Optical Transient Observer (GOTO) telescopes, which are located on opposite sides of the planet – on La Palma, in Spain’s Canary Islands, and Australia’s Siding Spring Observatory.

Summer Positions at the Vatican Observatory

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Image (Credit): The Vatican Observatory at San Gondolfo, Italy. (Vatican Observatory)

Does a summer studying astronomy in Rome sound interesting? If so, you might want to consider applying to be part of an astronomy program at the Vatican Observatory. The 440-year-old institution will be accepting 25 new applicants for the summer 2025 program.

Next summer’s program is titled “Exploring the Universe with JWST.” Here is a little more detail on the program:

Since the first release of data from the James Webb Space Telescope (JWST) in July 2022, we have witnessed a transformation in astronomy. VOSS 2025 will present a comprehensive overview of the major JWST results in its first three years (2022-2025), covering the four major scientific themes of JWST: (1) First Light and Reionization, (2) Assembly and Evolution of Galaxies, (3) Birth of Stars and Protoplanetary systems, and (4) Planetary Systems and the Origin of Life. In parallel, we will also provide a series of hands-on tutorials for JWST data processing and analysis. VOSS 2025 will convey the excitement of astronomical research in the era of JWST and the skills to pursue research projects spanning a broad range of themes in astrophysics.

The Catholic Church has come a long way since its treatment of Galileo. This observatory is just one example of the Church’s openness to the world around us.

You can read more about the 2023 summer program from the students themselves in this article.

Space Stories: Astronomical Damage in Ukraine, An Awakened Black Hole, and Understanding Jupiter’s Giant Red Spot

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Image (Credit): Stairwell of the Braude observatory’s main building with a painting of Alexei Leonov, the Soviet cosmonaut who performed the first spacewalk in 1965. (Science.org/Eric Lusito)

Here are some recent stories of interest.

—Science.org: “A Shattered Window to the Radio Sky“

In November 2023, photographer Eric Lusito made a rare visit to the Braude Radio Astronomy Observatory near Kharkiv, Ukraine, once one of the nation’s flagship scientific facilities. Since his visit, the Kharkiv region, which was partly occupied by Russian forces in 2022 but liberated later that year, has again faced a renewed Russian assault. As of this writing, military specialists say that effort has stalled. Here is Lusito’s account of his visit.

—The Guardian: “Astronomers Detect Sudden Awakening of Black Hole 1m Times Mass of Sun“

The mysterious brightening of a galaxy far, far away has been traced to the heart of the star system and the sudden awakening of a giant black hole 1m times more massive than the sun. Decades of observations found nothing remarkable about the distant galaxy in the constellation of Virgo, but that changed at the end of 2019 when astronomers noticed a dramatic surge in its luminosity that persists to this day. Researchers now believe they are witnessing changes that have never been seen before, with the black hole at the galaxy’s core putting on an extreme cosmic light show as vast amounts of material fall into it.

—University of the Basque Country: “Establishing Age and Origin of Jupiter’s Great Red Spot“

As a popular icon among objects in the Solar System, Jupiter’s Great Red Spot (GRS) is probably the best-known atmospheric structure. Its large size (right now its diameter is that of the Earth) and the contrast of its reddish colour against the planet’s pale clouds make it an object that can be easily seen even with small telescopes…Speculation about the origin of the GRS dates back to the first telescopic observations made by the astronomer Giovanni Domenico Cassini, who in 1665 discovered a dark oval at the same latitude as the GRS and named it the ‘Permanent Spot’ (PS), since it was observed by him and other astronomers until 1713. Track of it was subsequently lost for 118 years and it was not until 1831 and later years that S. Schwabe again observed a clear structure, roughly oval in shape and at the same latitude as the GRS; that can be regarded as the first observation of the current GRS, perhaps of a nascent GRS.

Space Stories: Spaceplane Planned for ISS, AI Assists Astronomy, and Water Older Than the Sun

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Image (Credit): Artist’s rendering of the Dream Chaser DC-100 spaceplane. (Sierra Space)

Here are some recent stories of interest.

—New Atlas: “World’s First Commercial Spaceplane in Final Stages Before Debut ISS Flight“

The world’s first winged commercial spaceplane has arrived at NASA’s Kennedy Space Center in Florida, its final destination before its first mission to the International Space Station (ISS) later this year. Following rigorous testing at Ohio’s Neil Armstrong Test Facility, the Dream Chaser DC-100 spaceplane named Tenacity got the green light to commence final pre-launch preparations, such as finishing its thermal protection system and payload integration, before it hitches a ride on a United Launch Alliance (ULA) Vulcan rocket to deliver 7,800 pounds (3,540 kg) of food, water and science experiments to the ISS.

—MIT Technology Review: “Astronomers are Enlisting AI to Prepare for a Data Downpour“

In deserts across Australia and South Africa, astronomers are planting forests of metallic detectors that will together scour the cosmos for radio signals. When it boots up in five years or so, the Square Kilometer Array Observatory will look for new information about the universe’s first stars and the different stages of galactic evolution.  But after syncing hundreds of thousands of dishes and antennas, astronomers will quickly face a new challenge: combing through some 300 petabytes of cosmological data a year—enough to fill a million laptops…In preparation for the information deluge, astronomers are turning to AI for assistance, optimizing algorithms to pick out patterns in large and notoriously finicky data sets. Some are now working to establish institutes dedicated to marrying the fields of computer science and astronomy—and grappling with the terms of the new partnership.

—BBC Sky at Night: “Earth’s Water is Even Older Than the Sun, Having Formed Billions of Years Ago, Say Astronomers“

How old is Earth’s water? Could it be older even than the planet itself? A team of astronomers say they’ve found the “missing link” that shows how water is delivered from gaseous star-forming regions in space to planets like Earth. The research suggests that Earth’s water is even older than the Sun. The news comes as a result of studies of a dusty planet-forming disc surrounding a star 1,300 lightyears from Earth