Exoplanetary motions imaged

Sixty light years away, in orbit of the second brightest star in the constellation of Pictor, a giant and relatively young planet has been glimpsed by the eyes of the European Southern Observatory.

Beta Pictoris is a star weighing in at 1.75 solar masses and only 12 million years old. Observations had previously shown that the star was surrounded by a dusty disc. As better instruments came along, improved observations suggested a warping of the disc and comets falling into the star, as if something was there perturbing their orbits. A giant planet perhaps?

Using the NAOS-CONICA instrument on one of the 8.2 metre telescopes that forms the ESO array, the Very Large Telescope, a team pictured a faint source near to the star in 2003. Without any way of differentiating a source that embedded in starlight as a planet or a small background star, the area was reimaged. In 2008 and the spring of 2009, the source had vanished. Later in 2009, it reappeared on the other side of the star, having either transitted it or passed behind it. Now the team were more sure they had a planet on their hands – and in a series of images.

The planet lies 8-15 times the Sun Earth distance, suggesting an orbit rather like Saturn. This means observations over 15-20 years should provide an orbit’s worth of data. The planet is around 9 times the mass of Jupiter and is the right size and position to explain the previous observations of warping of the disc. The young age of the system shows how quickly in stellar terms large planets can be produced and also give us an insight into such a system developing.

Beta Pictoris b, as the planet is called, joins a group of around ten exoplanets now imaged.

The announcement came in this paper.


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