Astronomers see birth of new exoplanet

Posted by Kate Taylor

Astronomers believe they have found a planet in the process of formation, clearing a path in the natal disc surrounding a young star.

Using ESO's Very Large Telescope, an international team has examined the short-lived disc of material around a young star, and for the first time found a smaller companion that could be responsible for the large gap found in the disc.

The transition from dust disc to planetary system is - in astronomical terms - pretty rapid and few objects are caught during this phase.

The team doesn't yet know whether it's found a planet or a brown dwarf.

T Chamaeleontis is a faint star in the small southern constellation of Chamaeleon that's similar to the Sun, but very near the beginning of its life. It lies about 350 light-years from the Earth and is only about seven million years old.

"Earlier studies had shown that T Cha was an excellent target for studying how planetary systems form," notes Johan Olofsson of the Max Planck Institute for Astronomy. "But this star is quite distant and the full power of the Very Large Telescope Interferometer (VLTI) was needed to resolve very fine details and see what is going on in the dust disc."

The astronomers found that some of the disc material formed a narrow dusty ring only about 20 million kilometres from the star. Beyond this inner disc, they found a region devoid of dust with the outer part of the disc stretching out into regions beyond about 1.1 billion kilometres from the star.

"For us the gap in the dust disc around T Cha was a smoking gun, and we asked ourselves: could we be witnessing a companion digging a gap inside its protoplanetary disc?" says Nuria Huélamo of Spain's Centro de Astrobiología.

Using a technique called sparse aperture masking, the team found the clear signature of an object located within the gap in the dust disc, about one billion kilometres from the star.

It's the first time an object much smaller than a star has been found within a gap in the planet-forming dust disc around a young star. The evidence suggests that it can't be a normal star, but could be either a brown dwarf surrounded by dust or, most excitingly, says ESO, a recently formed planet.