GP Comae Berenices, abbreviated to GP Com and also known as G 61-29, is a star system composed of 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 fro ...

orbited by a planetary mass object, likely the highly eroded core of another white dwarf star. The white dwarf is slowly accreting material from its satellite at a rate of /year and was proven to be a low-activity

AM CVn star An AM Canum Venaticorum star (AM CVn star), is a rare type of cataclysmic variable star named after their type star, AM Canum Venaticorum. In these hot blue binary variables, a white dwarf accretes hydrogen-poor matter from a compact companion s ...

. The star system is showing signs of a high abundance of

ionized Ionization, or Ionisation is the process by which an atom or a molecule acquires a negative or positive charge by gaining or losing electrons, often in conjunction with other chemical changes. The resulting electrically charged atom or molecule ...

nitrogen from the

accretion disk An accretion disk is a structure (often a circumstellar disk) formed by diffuse material in orbital motion around a massive central body. The central body is typically a star. Friction, uneven irradiance, magnetohydrodynamic effects, and other fo ...

around the primary.

Planetary system

The material emitted from the planetary mass companion is mostly helium, with a molar ratio of nitrogen up to 1.7%, very low neon levels and other elements not detectable at all. Approximately half of the luminosity of the system comes from the accretion disk. The planetary object is suspected to contain a

strange quark matter Strange matter (or strange quark matter) is quark matter containing strange quarks. In nature, strange matter is hypothesized to occur in the core of neutron stars, or, more speculatively, as isolated droplets that may vary in size from femtomete ...

core due to its unusually high density, which must be above to prevent tidal disruption; the theoretical bound for planets composed solely of ordinary matter is on the order of . The object's orbit is expected to decay within 100 million years due to

gravitational wave Gravitational waves are waves of the intensity of gravity generated by the accelerated masses of an orbital binary system that propagate as waves outward from their source at the speed of light. They were first proposed by Oliver Heaviside in 1 ...

emission.

References

{{Coma Berenices Planetary systems with one confirmed planet Coma Berenices J13054243+1801039 Comae Berenices, GP AM CVn stars White dwarfs