Three planets orbiting a nearby star

Three planets orbiting a nearby star

Fig. 16.9 . The speckled residual infrared light of a host star HD 8799 (center) and three orbiting planets (red dots) are found in this image taken in 2008 from the 10-meter Keck I telescope in Hawaii. The planets all orbit their star in the counter-clockwise direction, as indicated by the arrows, which show their positional displacement between 2004 and 2008. The planets, labeled b, c, and d, are located at distances of 70, 40 and 25 AU from the star, where the AU, or the astronomical unit, is the average distance between the Earth and the Sun. The distance of the inner planet is comparable to Neptune’s orbital distance at 30 AU. The star HR 8799 has a mass of about 1.5 times that of our own Sun, and is located about 130 light-years away. The planets most likely formed inside a protoplanetary disk about 60 million years ago. The planet masses are estimated as 7, 10 and 10 times that of Jupiter, for b, c and d respectively. (Courtesy of National Research Council, Canada, Christian Marois, Bruce Mcintosh and Keck Observatory.)

Copyright 2010, Professor Kenneth R. Lang, Tufts University