Astronomers Using ALMA Observe How Young Stars and Planets Grow
Posted on January 3, 2013
Astronomers using the Atacama Large Millimeter/submillimeter Array (ALMA) telescope have observed the growth of a young star and its planets. The HD142527 system is located about 450 light-years from Earth. An artist's conception of HD142527 system is pictured above.
When young stars form they pull in material from their surrounding clouds of gas and dust. This forms a flat, spinning disk around the star. Planets can start to form in the disk as small clumps. The planets increase in mass as they pull in additional material through their gravitational pull. This process results in a trail that clears out a gap in the disk. It has been a mystery as to how stars continue to grow even more massive with a gap in the disk. The ALMA observations show that this gap is never completely empty, but is instead filled with gas, which enables the star to continue to grow.
Simon Casassus, of the University of Chile and the Millennium Nucleus for Protoplanetary Disks, who led an international research team, says in a release, "This has been a bit of a mystery, but now we have found a process that allows the star to continue to grow despite the gap."
ALMA revealed streamers of dense gas (HCO+, or Formyl ion) crossing through the gap, which scientists say is probably pulled by the gravitational pull of the young forming planets.
Casassus says, "The most natural interpretation for the flows seen by ALMA is that the putative protoplanets are pulling streams of gas inward toward them that are channelled by their gravity. Much of the gas then overshoots the planets and continues inward to the portion of the disk close to the star, where it can eventually fall onto the star itself."