Planet birth witnessed for 1st time

For the first time, scientists believe they've detected the birth of a new world around a distant sun-like star.

If confirmed, the discovery, using the European Southern Observatory's Very Large Telescope, would provide scientists with the earliest view yet of how short-lived discs of material around young stars clump together in the early stages of planetary formation.

Astronomers studying T Chamaeleontis (T Cha), a faint star 350 light years from Earth in the southern constellation of Chamaeleon, detected a large gap in a disc of material around the star. They then found a small object in the disc which may be the cause of the gap.

The finding is detailed in two papers in the current edition of the Journal of Astronomy and Astrophysics.

Johan Olofsson from Germany's Max Planck Institute for Astronomy and lead author of one of the papers said the star was targeted because it's comparable to the sun, but at just seven million years old it's still near the beginning of its life.

"Earlier studies had shown that T Cha was an excellent target for studying how planetary systems form, but this star is quite distant and the full power of the Very Large Telescope was needed to resolve very fine details and see what is going on in the dust disc," Olofsson says.

Planets forming from dust

Scientists know planets form out of the discs of material around young stars, but theory says the transition from dust disc to planetary system is rapid and few objects are caught during this phase.

This is the first time a forming planet has been found in one of these transitional discs, although planets in more mature discs have been seen before.

Nuria Huelamo from the Centro de Astrobiologia, in Spain, and lead author of the second paper said the gap in the disc was the smoking gun.

"We asked ourselves: could we be witnessing a companion digging a gap inside its protoplanetary disc?"

After careful analysis they found the clear signature of an object located within the gap in the dust disc, about one billion kilometres from the star. That's slightly further out than Jupiter lies from our sun.

This is the first detection of an object much smaller than a star within a gap in the planet-forming dust disc around a young star.

Future observations will determine whether this is a planet or a brown dwarf, a gaseous body not big enough to begin the nuclear fusion process that makes stars shine.

Earliest evidence of planet building

Brad Carter, lecturer in physics at the University of Southern Queensland, said the observation is in line with current theory of planetary formation.

"It's a significant development, the earliest evidence of a dust disc transitioning to a planetary system."

"Unlike earlier discoveries of similar discs, this star is still very young and so tells us planets form very early on in the life of a star."

Planetary scientist Charley Lineweaver from the Australian National University, Mount Stromlo Observatory says it's beautiful to have such a nice confirmation of a planet emptying out a disc.

"What we are trying to do is trace the entire history of planetary formation from a gaseous disc, into a debris disc, into a planetary disc. All of these are steps which we think happen."

"It's like looking into a forest and not knowing where trees come from. And then one day, seeing a young tree and wondering if that's how fully grown trees start out."