Big planets get a head start in thin nurseries

Big planets get a head start in thin nurseries

Images of disk Oph163131 seen by ALMA (left) and HST (right). The boundaries of millimeter particles in the disc observed by ALMA are delineated in white. They are concentrated in a much narrower layer than the finer (micron-sized) dust observed by the Hubble Space Telescope. Credit: ALMA (ESO/NAOJ/NRAO) /Hubble/NASA/ESA /M. Villenave

Nurseries of ultra-thin planets have an increased chance of forming large planets, according to a study announced this week at the Europlanet Scientific Congress (EPSC) 2022 in Granada, Spain. An international team, led by Dr Marion Villenave of NASA’s Jet Propulsion Laboratory (JPL), observed a remarkably thin disc of dust and gas around a young star and found that its structure accelerated the clumping process. grains to form planets.

“Planets have only a limited chance of forming before the disk of gas and dust, their nursery, is dissipated by radiation from their parent star. The initial micron-sized particles composing the disc should grow rapidly into larger, millimeter-sized grains, the building blocks of planets.In this thin disc, we can see that the large particles have settled into a dense mid-plane, due to the effect combination of stellar gravity and interaction with gas, creating extremely favorable conditions for planetary growth,” explained Dr. Villenave.

Using the Atacama Large Millimeter Array (ALMA) in Chile, the team obtained very high-resolution images of the proto-planetary disk Oph163131, located in a nearby star-forming region called Ophiuchus. Their observations showed that although the disk is twice the diameter of our solar system, at its outer edge most of the dust is concentrated vertically in a layer only half the distance between Earth and the Sun. . This makes it one of the thinnest planetary nurseries observed to date.

“Looking at proto-planetary disks edge-on gives a clear view of vertical and radial dimensions, so we can unravel the dust evolution processes at work,” Villenave said. “ALMA gave us our first glimpse of the distribution of millimeter-sized grains in this disk. Their concentration in such a thin layer came as a surprise, as previous Hubble Space Telescope (HST) observations of finer particles the size of of one micron showed a region extending almost 20 times more.”

The team’s simulations based on observations show that the seeds of gas giant planets, which must have at least 10 Earth masses, can form in the outer part of the disk in less than 10 million years. This is within the typical lifetime of a planetary nursery before it dissipates.

“Thin planet nurseries appear to be favorable for the formation of large planets, and may even facilitate the formation of planets at large distances from the central star,” Villenave said. “Finding other examples of these thin disks could help to better understand the dominant mechanisms of the formation of wide-orbiting planets, an area of ​​research where there are still many open questions.”

Examination of oscillating shadows in protoplanetary disks

Provided by EuroPlanet

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