Astronomers using the Atacama Large Millimeter/sub-millimetre Array (ALMA) have observed the emission from dust grains in the protoplanetary disk around the infant star IRS 63. Their observations revealed two ring-like and two gap-like substructures in IRS 63’s disk.
This ALMA image shows young planet-forming dust rings around IRS 63. Image credit: D. Segura-Cox, Max Planck Institute for Extraterrestrial Physics.
IRS 63, also known as IRAS 16285-2355, is a protostar less than 500,000 years old in the L1709 region of the in the Ophiuchus molecular cloud, which is located 470 light-years away in the constellation of Ophiuchus.
It hosts a relatively large protoplanetary disk compared to disks — greater than 50 AU (astronomical units) — around other young stars.
“We observed the young protoplanetary disk called IRS 63 and found gaps and rings within the disk, which is indicative of planet formation,” said Dr. Ian Stephens, an astronomer in the Harvard & Smithsonian Center for Astrophysics.
“Traditionally it was thought that a star does most of its formation before the planets form, but our observations showed that they form simultaneously.”
“The rings in the disk around IRS 63 are very young,” said Dr. Dominique Segura-Cox, an astronomer at the Max Planck Institute for Extraterrestrial Physics.
“We used to think that stars entered adulthood first and then were the mothers of planets that came later.”
“But now we see that protostars and protoplanets grow and evolve together from early times, like siblings.”
The rings and gaps in the IRS 63 dust disk. Image credit: D. Segura-Cox, Max Planck Institute for Extraterrestrial Physics.
“The rings in the disk of IRS 63 are vast pile-ups of dust, ready to combine into planets,” said Dr. Anika Schmiedeke, also from the Max Planck Institute for Extraterrestrial Physics.
“However, even after the dust clumps together to form a planet embryo, the still-forming planet could disappear by spiraling inwards and being consumed by the central protostar.”
“If planets do start to form very early and at large distances from the protostar, they may better survive this process.”
The observations also revealed implications for understanding the formation of our own Solar System.
It takes at least 10 Earth masses of solid material to form a planet core capable of accreting enough gas to form a gas giant.
While researching IRS 63 the team found that the young disk contains roughly 150 Earth masses of dust and material.
Paired with the rings and gaps present in the disk, the authors are learning a lot about the early formation of planets.
This image from ESA’s Herschel Space Telescope shows the L1709 region in the Ophiuchus molecular cloud. Image credit: D. Segura-Cox, Max Planck Institute for Extraterrestrial Physics / ESA / Herschel / SPIRE / PACS / D. Arzoumanian.
“These results show that we must focus on the youngest systems to truly understand planet formation,” said Dr. Jaime Pineda, also from the Max Planck Institute for Extraterrestrial Physics.
“For example, there is growing evidence that Jupiter may have actually formed much farther out in the Solar System, beyond the Neptune orbit, and then migrated inwards to its present location.”
“Similarly, the dust surrounding IRS 63 shows that there is enough material far from the protostar and at a stage young enough that there is a chance for this analogue of the Solar System to form planets in the way that Jupiter is suspected to have formed.”
“The size of the disk is very similar to our own Solar System,” Dr. Segura-Cox added.
“Even the mass of the protostar is just a little less than our Sun’s. Studying such young planet-forming disks around protostars can give us important insights into our own origins.”
The findings were published in the journal Nature.
D.M. Segura-Cox et al. 2020. Four annular structures in a protostellar disk less than 500,000 years old. Nature 586, 228-231; doi: 10.1038/s41586-020-2779-6