GD 61 is a

white dwarf A white dwarf is a stellar core remnant composed mostly of electron-degenerate matter. A white dwarf is very dense: its mass is comparable to the Sun's, while its volume is comparable to the Earth's. A white dwarf's faint luminosity comes ...

with a planetary system located 150 light-years from Earth in the constellation Perseus. It is thought to have been a main-sequence star of spectral type A0V with around three times the mass of the Sun that has aged and passed through a

red-giant A red giant is a luminous giant star of low or intermediate mass (roughly 0.3–8 solar masses ()) in a late phase of stellar evolution. The outer atmosphere is inflated and tenuous, making the radius large and the surface temperature around o ...

phase, leaving a dense, hot remnant that has around 70% of the Sun's mass and a surface temperature of 17,280 K. It is thought to be around 600 million years old, including both its life as a main-sequence star and as a white dwarf. It has an apparent magnitude of 14.8. GD 61 was first noted as a potential degenerate star in 1965, in a survey of white-dwarf suspects by astronomers from the Lowell Observatory in Arizona. In 2013, a circumstellar disk that resulted from the destruction of a water-rich asteroid was detected in close orbit around GD 61, which makes this the first detection of solid or liquid water on an extrasolar body. This asteroid would originally have been 26% water by mass, close to the water content of

Ceres Ceres most commonly refers to: * Ceres (dwarf planet), the largest asteroid * Ceres (mythology), the Roman goddess of agriculture Ceres may also refer to: Places Brazil * Ceres, Goiás, Brazil * Ceres Microregion, in north-central Goiás ...

.Evidence for water in the rocky debris of a disrupted extrasolar minor planet
/ref> 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. The researchers used the

Cosmic Origins Spectrograph The Cosmic Origins Spectrograph (COS) is a science instrument that was installed on the Hubble Space Telescope during Servicing Mission 4 ( STS-125) in May 2009. It is designed for ultraviolet (90–320 nm) spectroscopy of faint point sources ...

on the Hubble Space Telescope to determine the elemental composition. The elements magnesium, silicon, iron, and oxygen were detected, all components of rocky planets, although the levels of oxygen were much higher than what could be accounted for. The lack of associated carbon left only one candidate for the oxygen excess—water.

References

{{Stars of Perseus White dwarfs Astrobiology 20131012 Perseus (constellation)

See also

References