News in Science

Scientists witness birth of a planet

New world Astronomers have for the first time captured images of a planet forming around a star, which could shed light on the way in which planets and solar systems form.

The discovery has been accepted for publication in the Astrophysical Journal and appears on the pre-press physics website arXiv.org.

Dr Michael Ireland from Sydney's Macquarie University is part of an international team of astronomers who made the discovery. They used the giant 10-metre Keck telescope in Hawaii to study a very young, newly formed star called LkCa15 in the Taurus-Auriga star forming region, about 450 light years way.

The star is almost the same size as the Sun, but only a few million years old.

Ireland and colleagues targeted LkCa15 because the surrounding planetary dust and gas disk has a large gap in it.

"When we took a closer look, we found two blobs, one was a planet, the other was the gas and dust falling onto the planet," says Ireland.

The newly discovered planet which has been named LkCa15-b, is a gas giant similar to Jupiter.

It orbits its host star at about the same distance that Uranus orbits our Sun - 20 times further out than the Earth's orbit.

Astronomers are still trying to determine the infant planet's size.

"Its upper limit is about seven times the mass of Jupiter, while its lower limit would be about the mass of Saturn," says Ireland.

"There have been quite a few detections of Jupiter-like planets in recent years, but we've caught this one at the beginning of its life-cycle, that's something special."

According to Ireland, it's the first time astronomers have been able to see a planet surrounded by dust and gas.

"This dusty matter is either falling onto the planet's surface through accretion, or it's being ejected from the planet by electromagnetic forces."

Understanding our own history

He says studying newly formed solar systems helps astronomers better understand our own solar system.

"LkCa15 is a very big disk with big planets a long way out and I expect that to be very common, big disks mean big planets forming further out," says Ireland. "So the question is, why is our solar system so small?"

He says one possible explanation is that a star may have passed close to our solar system when it was young, drawing away material making it a relatively small disk.

"If that didn't happen, would there have been more cometary impacts on the terrestrial planets?" Ireland asks. "If so, would that have been good for life?"