WD 1145+017

Coordinates: 11^h 48^m 33.63^s, +01° 28′ 59.4″

WD 1145+017^[2] (also known as EPIC 201563164^[3]) is a white dwarf approximately 570 light-years (170 pc) from Earth in the constellation of Virgo. It is the first white dwarf to be observed with a transiting planetary-mass object orbiting it.^[7][8]

Stellar characteristics[]

The white dwarf has a mass of 0.6 M_☉, radius of 0.02 R_☉ (1.4 R_Earth) and a temperature of 15,020 K, typical for white dwarf stars. It has been a white dwarf for 224 million years.^[5][9] The star included strong absorption lines due to magnesium, aluminium, silicon, calcium, iron and nickel. These elements commonly found in rocky planets are polluting the surface of the star, and would normally be expected to mix through the star and disappear from view after a million years.^[9]

A circumstellar dust cloud and disk (likely due to disintegrating asteroids, located at 97 to 103 R_wd, and emitting thermal IR radiation) surrounds the star. In addition, a circumstellar gas disk (located ~ 25 to 40 R_wd, and undergoing relativistic precession with a period of ~ 5 years) surrounds the star as well.^[10][11]

Based on recent studies and calculations, it is believed that the star initially was an early A-type main sequence star with a mass of about 2.46 M_☉, remaining so for an estimated 550 million years.^[5] Afterwards, following the exhaustion of hydrogen within its core, it evolved and expanded into a red giant before eventually ejecting its layers and contracting into a white dwarf, and has gradually cooled over the last 224 million years. This gives the star an estimated total age of around 774 million years.^[5][12]

The apparent magnitude of the star, or how bright it appears from Earth's perspective, is about 17. Therefore, it is too dim to be seen with the naked eye.

Planetary system[]