Template:POTD/2019-11-13
HR 8799 is a roughly 30-million-year-old main-sequence star located 129 light-years (39.6 parsecs) away from Earth in the constellation of Pegasus. It has roughly 1.5 times the Sun's mass and 4.9 times its luminosity, and is part of a system that also contains a debris disk and at least four massive planets. Those planets, along with Fomalhaut b, were the first exoplanets whose orbital motion was confirmed via direct imaging. The star is a Gamma Doradus variable: its luminosity changes because of non-radial pulsations of its surface. It is also classified as a Lambda Boötis star, which means its surface layers are depleted in iron peak elements.
This video shows the HR 8799 planetary system across a period of seven years, with motion interpolation used on seven images captured between 2009 and 2016 by the W. M. Keck Observatory in Hawaii. The light from the star, in the center, is obscured to allow the four orbiting planets to be seen. From innermost to outermost, the planets are designated e (center right), d (bottom right), c (top right), and b (top left).Video credit: Jason Wang et al.; edited by Benjamin Hunt and Jan-Eric Nyström