Discovery of giant gas cloud around distant star raises questions
Scientists have made a discovery that has raised some questions about the conventional theory of planet formation. Astronomers using ALMA have discovered a young star that is surrounded by a huge amount of gas. The star is 49 CETI, and it is 40 million years old. According to conventional theories of planet formation that giant gas cloud should have disappeared by that age.Scientists are having to rethink the current understanding of planet formation after the discovery. Current theories say that as time goes by, the gas in a disk is either incorporated into planets or blown away by radiation pressure from the central star. In the end, the star ends up surrounded by planets and a disk of dusty debris.
The dusty disk is the signal that planet formation is nearly finished. Scientists say that some debris discs still contain some amount of gas. If that gas remains long enough, the debris disks and planetary seeds may have enough time and material to evolve gas giants like Jupiter.
Around 49 Ceti, the team discovered atomic carbon gas. After making observations with other radio telescopes, the team used ALMA and found that the disk around the star had about ten times more gas than previously estimated. The team learned that the star had an abundance of a rare form of carbon called 13C, the first detection of the type of carbon in any astronomical object.
The origin of the gas is a mystery, but there are two leading possibilities. One is that the gas is a remnant that survived the dissipation process in the final phase of planet formation. The other possibility is that the gas was released by collisions of small bodies like comets. However, the amount of gas around the star is too large to be accommodated by current theories.