Thursday, June 17, 2010

A big expoplanet in a wide orbit

The circled dots indicate the 8 Jupiter mass planet that was discovered by David Lafrenière and colleagues as it orbits the star 1RXS J160929.1-210524. A preprint is also available. These infrared images of the system are acquired at wavelengths of 3 (left) and 4 (right) microns. This giant exoplanet orbits about 300 AU away from the primary star (cross), which is quite remarkable, because current models of planet formation generally do not produce such large planets orbiting at such great distances from the star. However, binary stars do exist at these separations, so one might wonder whether these objects really are large exoplanets, or are perhaps rather small stars.

Sunday, June 13, 2010

Giant exoplanet confirmed orbiting in debris disk

Beta Pictoris b is a giant extrasolar planet, having a mass of about 10 Jupiter masses. It was first detected by direct imaging in 2003, but not seen again in followup images acquired in 2008, so the suspicion then was that this faint dot was just a background star, and not a planet that is actually bound to the star. However that expolanet was later recovered again in images acquired in late 2009 by Anne-Marie Lagrange; those images show that the dot seen above is indeed bound to Beta Pictoris, and orbits at a distance of about 10 AU from the star. So it seems that beta Pic b wasn't seen in 2008 because it was passing in front of or behind the very much brighter star.

Beta Pictoris is also known for its huge circumstellar debris disk; that disk is seen edge-on by astronomers at Earth, and the above graphic---which by the way is not a real telescopic image, but is probably the merger of two separate images---shows that the planet's orbit is coplanar with the debris disk. This in fact is to be expected, because such debris disks are composed of dust grains that are produced by collisions among unseen planetesimals, which are also the seeds from which planets form from. See this press release from the European Southern Observatory for more details.

Friday, June 4, 2010

Another impact at Jupiter!

Anthony Wesley does it again! This time, by recording a video what appears to be another small impact at Jupiter, presumably by an unseen comet or asteroid. Recall that Anthony was also the amateur astronomer who spotted as asteroid impact at Jupiter in July 2009. See New Scientist for a video of the explosion by another amateur astronomer, Christopher Go.