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Tuesday, March 8, 2011

Planet caught in formation

Planets are formed when the swirling dust and gas that circles young stars coalesces into solid bodies. For the first time, astronomers have found what they believe is a planet in the process of formation.

The star T Chamaeleontis (T Cha) is a very young star (seven million years old) located about 350 light years from Earth. Like many young stars, it is surrounded by a ring of dust. However, astronomers led by Johan Olofsson of the Max Planck Institute were able to discern a gap in that disk. They used an instrument called the Very Large Telescope (VLT) Interferometer to observe that the star was encircled by dust at a distance of about 20 million kilometers, and again at about 1.1 billion kilometers. The space between those two rings was largely devoid of dust.

There are a number of mechanisms that can account for the dissipation of dust around a star, including planet formation. Nuria Huélamo of Centro de Astrobiología and a team of astronomers used another instrument on the VLT to find such a planet. The candidate object was located about a billion kilometers from T Cha, near the outer edge of the dust gap. The scientists aren’t sure yet whether the object will turn out to be a brown dwarf surrounded by dust or a planet.

In any case, this is the first example of an object in the process of clearing a path around a star by accreting all the dust and gas within that region.

Caption: This artist’s impression shows the disc around the young star T Cha. Using ESO’s Very Large Telescope this disc has been found to be in two parts, a narrow ring close to the star and the remainder of the disc material much further out. A companion object, seen in the foreground, has been detected in the gap in the disc that may be either a brown dwarf or a large planet. The inner dust disc is lost in the glare of the star on this picture.

Credit: ESO/L. Calçada