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Astronomers using the NSF’s Karl G. Jansky Very Large Array and the Atacama Large Millimeter/submillimeter Array have detected 97 discs of gas and dust around young protostars in the constellation Orion, home to star-forming regions. stars closest to Earth.
This image shows the molecular clouds of Orion, the target of the VANDAM investigation; the yellow dots are the locations of the protostars observed on a blue background image made by Herschel; the side panels show six young protostars imaged by ALMA (blue) and the VLA (orange). Image credit: NRAO/AUI/NSF.
“Stars form from clouds of gas and dust that collapse under the force of their own gravity,” said lead author Dr. Patrick Sheehan, an astronomer at Northwestern University and National Radio. Astronomy Observatory, and colleagues.
“Because of the initial angular momentum of the collapsing material, much of the material in the cloud forms into a disk rather than collapsing directly onto the star forming in the center.”
“Matter is then accreted through the disk onto the star, which in turn regulates much of the eventual buildup of stellar mass.”
“Furthermore, it is in these protostellar disks that planets are thought to form, and so understanding their properties throughout their evolution is crucial to understanding how planets form.”
To better understand this process, astronomers conducted a radio survey of young stars in the molecular clouds of Orion, a giant star-forming region about 1,400 light-years from Earth in the constellation Orion. .
They analyzed data collected by the Very Large Array (VLA) and the Atacama Large Millimeter/submillimeter Array (ALMA).
“Although the dust surrounding young stars blocks most visible light, it is more transparent to radio light,” the researchers noted.
“Therefore, the radio observations from the VLA and ALMA have given us a detailed view of young star systems.”
The survey is known as the VLA/ALMA Nascent Disk and Multiplicity (VANDAM) survey, the largest survey of young stars ever.
“With the VANDAM survey, we measured the size and mass of many young protoplanetary disks and compared them to older disks that ALMA has previously studied,” the scientists said.
“One of the things we’ve found is that younger drives are generally more massive than older drives of the same size.”
“This makes sense because as a star forms, it picks up more material nearby, reducing the mass of its surrounding disk.”
“But it also implies that the largest worlds in a planetary system begin to form early when the protoplanetary disk is denser.”
Older protoplanetary disks generally contain rings where there is much less material.
These disc gaps are often regions where planets form, but they could also indicate a resonant structure in the disc, where the gravitational tug of young planets causes gaps to form, similar to how Jupiter creates orbital gaps. in the asteroid belt.
The authors found similar spacing structures in discs as young as 100,000 years old, which is surprisingly early.
“During the first million years of a system, the structure of a disk is similar to that of older disks,” they said.
“A few of the systems observed in the VANDAM survey were very irregularly shaped.”
“It is possible that these systems are so young that a disk system has not begun to form.”
“It could also be that even the protostar hasn’t fully taken shape.”
The team’s article will be published in the Astrophysical Journal.
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Patrick D. Sheehan et al. 2022. The VLA/ALMA Nascent Disk and Multiplicity (VANDAM) Survey of Orion Protostars VI. Insights into radiative transfer modeling. ApJ, in the press; arXiv: 2203.00029
