The formation of giant planets has traditionally been divided into two pathways: core accretion and gravitational instability. However, in recent years, gravitational instability has become less favored, primarily due to the scarcity of observations of fragmented protoplanetary disks around young stars and the low occurrence rate of massive planets on very wide orbits. Astronomers using ESO’s Very Large Telescope and the Atacama Large Millimeter/submillimeter Array have now spotted large dusty clumps — close to the young star V960 Mon — that could collapse to create giant planets. They suggest this observation is the first evidence of gravitational instability occurring on planetary scales.
V960 Mon is located over 5,000 light-years away from Earth in the constellation of Monoceros.
Also known as 2MASS J06593158-0405277, this star attracted astronomers’ attention when it suddenly increased its brightness more than twenty times in 2014.
Further observations with the Spectro-Polarimetric High-contrast Exoplanet REsearch (SPHERE) instrument on ESO’s Very Large Telescope (VLT) revealed that the material orbiting V960 Mon is assembling together in a series of intricate spiral arms extending over distances bigger than the entire Solar System.
The finding motivated astronomers to analyze archival observations of the V960 Mon system made with ALMA.
The VLT observations probe the surface of the dusty material around the star, while ALMA can peer deeper into its structure.
“With ALMA, it became apparent that the spiral arms are undergoing fragmentation, resulting in the formation of clumps with masses akin to those of planets,” said Dr. Alice Zurlo, an astronomer at the Universidad Diego Portales.
Astronomers believe that giant planets form either by core accretion, when dust grains come together, or by gravitational instability, when large fragments of the material around a star contract and collapse.
While they have previously found evidence for the…
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