Astronomers have found that several debris disk still possess some amount of gas.
Astronomers found a young star surrounded by a huge mass of gas using the Atacama Large Millimetre. The star, 49 Ceti is a 40 million years old star and conventional theories of planet formation could predict that the gas should have disappeared by that age. The large amount of gas requests a reconsideration of our current understanding of planet formation.
Planets form in gaseous disks called protoplanetary disks around young stars. The dust particles come together to form Earth-like planets or they becomes cores of other massive planets by collecting large amounts of gas from the disk to form Jupiter-like gaseous giant planets. According to the currently existing theories, as time passes, the gasses in the disks are either incorporated into planets or get blown away because of radiation pressure from the central star. Eventually, the star is surrounded by planets and a disk of dusty debris. These dusty disks, called debris disks imply that planet formation is almost finished.
Recent advancements in radio telescopes have uncovered a surprise. Astronomers have discovered that several debris disks still possess some amount of gas. If the gas remains in the debris disk for long, planetary seeds may have enough time and material to evolve into giant planets like Jupiter. "We found atomic carbon gas in the debris disk around 49 Ceti by using more than 100 hours of observations on the ASTE telescope," says Aya Higuchi, an astronomer at the National Astronomical Observatory of Japan (NAOJ). ASTE is a 10-m diameter radio telescope in Chile operated by NAOJ. "As a natural extension, we used ALMA to obtain a more detailed view, and that gave us the second surprise. The carbon gas around 49 Ceti turned out to be 10 times more abundant than our previous estimation."