Wednesday, May 6, 2009

Image of planet orbiting Fomalhaut

This remarkable image shows the motion of the Jupiter-mass planet as it orbits the star Fomalhaut (see inset). This optical image was acquired by Paul Kalas (UC Berkeley) and colleagues using the Hubble Space Telescope. Interestingly, this star also harbors a dusty circumstellar debris disk. The planet orbits just inside a gap within this disk, and its gravity is responsible for keeping that gap clear of dust. Note also that the debris disk appears to resemble a ring, due to the disk's inner edge being illuminated by the central star. The dust in these debris disks is thought to be generated by collisions among unseen planetesimals (eg, asteroids or comets) that also probably orbit within this disk. The ellipse in this graphic has a radius of 30 AU (1 AU = Sun-Earth distance), which is the radius of Neptune's orbit. The radius of the disk's inner edge is about 140 AU, which is about 3 times larger than the size of our Solar System's Kuiper Belt, which is also a belt of comets orbiting just beyond Neptune.

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