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: More Quality Control Issues at Boeing, Blue Origin’s Planned Lunar Landing, and Citizen Scientists Assisting with Exoplanet Research

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Image (Credit): Artist’s rendering of the SLS in flight. (NASA)

Here are some recent stories of interest.

—NBC News: “NASA Inspector General Gives Damning Assessment of Boeing’s Quality Control in New Report“

The report, released Thursday by NASA’s Office of Inspector General, calls into question Boeing’s standards and quality control for its part in NASA’s efforts to return astronauts to the moon. In NASA’s development of its next-generation megarocket, known as the Space Launch System, it gave Boeing the contract to build the rocket system’s powerful upper stage. But according to the report, Boeing’s quality control systems fall short of NASA’s requirements, and some known deficiencies have gone unaddressed. What’s more, the workers on the project are not, as a whole, sufficiently experienced or well trained, according to the inspector general.

—Space News: “NASA Payload to Fly on First Blue Origin Lunar Lander Mission“

A NASA payload will hitch a ride to the moon on Blue Origin’s first lunar lander mission, scheduled to launch as soon as next March. In an Aug. 6 procurement filing, NASA revealed it selected Blue Origin to fly a camera system to study how engine plumes interact with regolith at south polar regions of the moon, collecting data to support future crewed landing missions. The payload, called Stereo Cameras for Lunar Plume Surface Studies (SCALPSS), will fly through NASA’s Commercial Lunar Payload Services (CLPS) program.

—NASA: “How NASA Citizen Science Fuels Future Exoplanet Research“

NASA’s upcoming flagship astrophysics missions, the Nancy Grace Roman Space Telescope and the Habitable Worlds Observatory, will study planets outside our solar system, known as exoplanets. Over 5,000 exoplanets have been confirmed to date — and given that scientists estimate at least one exoplanet exists for every star in the sky, the hunt has just begun. Exoplanet discoveries from Roman and the Habitable Worlds Observatory may not be made only by professional researchers, but also by interested members of the public, known as citizen scientists.

Space Stories: A Polish Astronaut Heads to ISS, Two Astronauts Are Missing from Church, and Deadly Red Dwarves

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Image (Credit): Sławosz Uznański in ESA’s Neutral Buoyancy Facility. (ESA)

Here are some recent stories of interest.

—European Space Agency (ESA): “Sławosz Uznański from Poland Will fly to International Space Station on Rourth Axiom Space Mission“

Axiom Space announced that it is partnering with India, Hungary, and with Poland through ESA to send three national astronauts to the International Space Station on Axiom Mission 4 (Ax-4). ESA project astronaut Sławosz Uznański has been assigned as mission specialist under the command of Axiom Space’s Chief Astronaut Peggy Whitson...The other two Ax-4 crew members are pilot Shubhanshu Shukla from India, and mission specialist Tibor Kapu from Hungary.

—Associated Press: “One Church, Two Astronauts. How a Texas Congregation is Supporting its Members on the Space Station“

…there’s no way on Earth for NASA astronauts Barry “Butch” Wilmore and Tracy Dyson to show up at Providence Baptist Church. They’re in space, orbiting the planet. More specifically, these two members are working on the International Space Station together...Dyson’s six-month mission isn’t scheduled to end until September, but Wilmore and his fellow NASA test pilot, Suni Williams, should have been back weeks ago. They are staying longer than expected following thruster failures and helium leaks on Boeing’s inaugural crew flight for its Starliner capsule. Wilmore and Williams have said they are confident the capsule will return them home safely; engineers are still poring over Starliner test data.

—University of Cambridge: “Astronomers Uncover Risks to Planets that Could Host Life“

Astronomers have discovered that red dwarf stars can produce stellar flares that carry far-ultraviolet (far-UV) radiation levels much higher than previously believed. The discovery suggests that the intense UV radiation from these flares could significantly impact whether planets around red dwarf stars can be habitable…According to researchers, UV radiation from stellar flares can either erode planetary atmospheres, threatening their potential to support life, or contribute to the formation of RNA building blocks, which are essential for the creation of life.

Pic of the Week: View of a Nearby Exoplanet

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Image (Credit): JWST’s view of exoplanet Epsilon Indi Ab. (NASA, ESA, CSA, STScI, E. Matthews (Max Planck Institute for Astronomy))

This week’s image looks dark and simple, and yet it is an amazing sight provided by NASA’s James Webb Space Telescope (JWST). It shows a directly imaged exoplanets that resides about 12 light-years from us. It is called Epsilon Indi Ab and is several times the mass of Jupiter.

Here is an explanation from NASA about what you are seeing in the image:

This image of the gas-giant exoplanet Epsilon Indi Ab was taken with the on NASA’s James Webb Space Telescope’s MIRI (Mid-Infrared Instrument). A star symbol marks the location of the host star Epsilon Indi A, whose light has been blocked by the coronagraph, resulting in the dark circle marked with a dashed white line. Epsilon Indi Ab is one of the coldest exoplanets ever directly imaged. Light at 10.6 microns was assigned the color blue, while light at 15.5 microns was assigned the color orange. MIRI did not resolve the planet, which is a point source.

Space Stories: Good Time to View the Heavens, Nearby Super-Jupiter, and Spotting Deepfakes

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Credit: Vikash Kr Singh from Pixabay

Here are some recent stories of interest.

—Live Science: “Why the 1st Week of August is the Best Time to See ‘Shooting Stars’ and the Milky Way — No Telescope Required“

The arrival of August means two things for stargazers — “shooting stars” and the Milky Way. In 2024, you can see both at the same time if you know exactly where and when to look…This month, there’s a new moon on Aug. 4, which will keep the post-sunset sky dark until about Aug. 8. That makes the first week of August ideal for spotting “shooting stars” — while you also look for the Milky Way. True darkness won’t come until midnight for most of the Northern Hemisphere, but look to the southeast after dark, and you’ll have a chance of seeing the Sagittarius arm of the Milky Way arching across the night sky.

—Max Planck Institute for Astronomy: “Webb Images Nearest Super-Jupiter, Opening a New Window to Exoplanet Research“

Using the James Webb Space Telescope (JWST), an MPIA-led team of astronomers imaged a new exoplanet that orbits a star in the nearby triple system Epsilon Indi. The planet is a cold super-Jupiter exhibiting a temperature of around 0 degrees Celsius and a wide orbit comparable to that of Neptune around the Sun. This measurement was only possible thanks to JWST’s unprecedented imaging capabilities in the thermal infrared. It exemplifies the potential of finding many more such planets similar to Jupiter in mass, temperature, and orbit. Studying them will improve our knowledge of how gas giants form and evolve in time.

—Nature: “AI ‘Deepfake’ Faces Detected Using Astronomy Methods“

Researchers are turning to techniques from astronomy to help spot computer-generated ‘deepfake’ images — which can look identical to genuine photographs at first glance. By analysing images of faces using methods that are usually used to survey distant galaxies, astronomers can measure how a person’s eyes reflect light, which can reveal telltale signs of image manipulation.