Artist's impression of a flared proto-planetary disk.
Credit: European Southern Observatory
SYDNEY: A flaring disc of dust, debris and gas has been discovered around a star two and a half times larger than our Sun, offering unique insights into the evolution of planets, researchers say.
"Planets form in massive, gaseous and dusty proto-planetary discs that surround nascent stars,” said Pierre-Olivier Lagage, the French astrophysicist who led the study, published in the U.S. journal Science. "However, very little is known about these disks, especially those around stars more massive than the Sun."
An international team of astronomers discovered the flared disc around a star called HD97048, which is located in the Chameleon I dark cloud, 600 light-years away. The star is 40 times more luminous than our Sun and is 2.5 times as massive. Until now, scientists were unsure whether such discs formed around stars larger than our Sun.
Although a recent study claimed HD97048 was about one million years old, the extent of gas and dust around the star suggests the disc is still relatively young, according to Lagage. “There are several physical mechanisms which reduce the amount of gas and dust with time,” he said. “Observing both a large amount of gas and dust is the main argument to claim that the disc is in an early stage of evolution.”
Lagage and colleagues believe that this flared disc offers a rare opportunity to witness the conditions prevailing prior to or during planet formation, where dust particles coalescese. “There is a large amount of dust in the disc ... more than enough to make planets,” said Lagage.
The astronomers used the VISIR instrument (Very large telescope Imager and Spectrometer for the InfraRed) on the European Southern Observatory's Very Large Telescope to map in the infrared the disc surrounding the star.
They were able to achieve a very detailed view due to the high angular resolution offered by the 8-metre long telescope. The disc is at least 12 times more extended than the orbit of Neptune, the most distant planet in our Solar System. "This is the first time such a structure, predicted by some theoretical models, [has been] imaged around a massive star," said Lagage.
Such a geometry can only be explained if the disc contains a large amount of gas, in this case, at least as much as 10 times the mass of Jupiter. It should also contain more than 50 Earth masses in dust.
"From the structure of the disc, we infer that planetary embryos may be present in the inner part of the disk," said Lagage. "We are planning follow-up observations at higher angular resolution in order to probe these regions."
With the European Southern Observatory
