​Stellar "amniotic sac" hints at our solar system's beginnings

Observations of a young star, just one one-thousandth the age of our sun, may shed light on how our solar system first came to be 4.5 billion years ago.

Using Chile's Very Large Telescope Interferometer, scientists have peered into the "amniotic sac" of a still-forming star that is host to at least one protoplanet, giving them a glimpse of conditions that may mirror those at the formation of our own planetary system. The findings were published Monday in the Monthly Notices of the Royal Astronomical Society.

"Nobody has ever been able to probe this close to a star that is still forming and which also has at least one planet so close in," said lead author Dr Ignacio Mendigutía, of the School of Physics and Astronomy at the University of Leeds, in a statement. "We have been able to detect for the first time emission from the innermost part of the disk of gas that surrounds the central star."

The young star, called HD 100546, is 325 light-years from Earth. Coauthor Rene Oudmaijer, also from Leeds, said that observing it was a challenge "similar to trying to observe something the size of a pinhead from 100 kilometers away."

HD 100546 is surrounded by a disk of gas and dust called a protoplanetary disk, in which planets are formed. Disks like these are common, but this one is odd in a couple ways. For one, it has a big empty gap in it.

"We suggest that the gravitational influence of the still-forming planet -- or possibly planets -- in the gap could be boosting a transfer of material from the gas-rich outer part of the disk to the inner regions," Mendigutía said.

What's more, it is exceedingly rare to find a system that has both a gap and a planet within the protoplanetary disk. The only other known example is in a system in which the gap is ten times further from the parent star.

"With our observations of the inner disk of gas in the HD 100546 system, we are beginning to understand the earliest life of planet-hosting stars on a scale that is comparable to our solar system," said Oudmaijer.