GD 61 is a white dwarf with a planetary system 150 light-years from Earth in the constellation Perseus.[3] Originally thought to have been a main sequence star of spectral type A0V with around triple the mass of our sun, it has aged and passed through a red giant phase, leaving a dense hot remnant that has around 70% of our Sun's mass and a surface temperature of 17280 K. It is thought to be around 600 million years old, including both its life as a main sequence star and white dwarf stellar remnant.[4] It has an apparent magnitude of 14.8.[2]
An asteroid in the system was detected in 2013 that contains water, the first detection of solid or liquid water on an extrasolar body. The asteroid, the first extrasolar asteroid detected, is 26% water by mass, close to the water content of Ceres. This evidence suggests that a planet, with a rocky surface similar to Earth's, may have existed in the past, with the asteroid thus being an artifact from this period, now possibly part of a debris field from the hypothetical planet's breakup. Such a planet would have had both a rocky surface and water, two key ingredients for life.[5][6][7]
Detection
Data from NASA's Hubble and FUSE telescopes, and from the Keck Observatory in Hawaii, were used to detect and observe the asteroid.
^Farihi, J.; Brinkworth, C. S.; Gänsicke, B. T.; Marsh, T. R.; Girven, J.; Hoard, D. W.; Klein, B.; Koester, D. "Possible Signs of Water and Differentiation in a Rocky Exoplanetary Body". The Astrophysical Journal Letters. 728 (1): L8–L13. Bibcode:2011ApJ...728L...8F. doi:10.1088/2041-8205/728/1/L8.{{cite journal}}: CS1 maint: multiple names: authors list (link)
