Astronomers have spotted a system that could reveal a key stage in the formation of giant planets. For the first time, images of vast gas streams flowing across a gap in the accretion disc of a young star have been seen.
The new research, published today in the journal Nature, shows that the gas streams found around a star named HD 142527 may have been created by giant planets that "guzzle" gas from the outer ring as they grow. The disc around the star is divided into an inner and outer ring. The gap between the two is thought to have been made by newly forming gas giant planets. Astronomers had theorized that streams of dust from outer discs might connect the two rings.
“Astronomers have been predicting that these streams must exist, but this is the first time we’ve been able to see them directly,” said Simon Casassus, an astronomer at the University of Chile who led the research. “Thanks to the new ALMA telescope, we’ve been able to get direct observations to illuminate current theories of how planets are formed!”
The ALMA (Atacama Large Millimeter/submillimeter Array) telescope was able to examine HD142527 in greater detail than ever before, and with less glare from the star. Though the gap between discs was already known of, the diffuse gas and denser streams of gas found between the discs has now been observed. In addition, Astronomers found that the rate at which the gas streams into the inner disc is "just right" to keep the inner disc replenished, feeding the still-forming star.
“We think that there is a giant planet hidden within, and causing, each of these streams," said Sebastián Pérez, a team member on the research. "The planets grow by capturing some of the gas from the outer disc, but they are really messy eaters: the rest of it overshoots and feeds into the inner disc around the star."
Though it is theorized that forming gas giants are responsible for the streams, the team was unable to detect such planets directly.
“We searched for the planets themselves with state-of-the-art infrared instruments on other telescopes," said Casassus. "However, we expect that these forming planets are still deeply embedded in the streams of gas, which are almost opaque. Therefore, there may be little chance of spotting the planets directly.”
(Image courtesy ESO)