KOI-74 () is an
eclipsing binary
A binary star or binary star system is a Star system, system of two stars that are gravity, gravitationally bound to and in orbit around each other. Binary stars in the night sky that are seen as a single object to the naked eye are often resolved ...
star in the constellation of
Cygnus. The primary star is an
A-type main-sequence star
An A-type main-sequence star (A) or A dwarf star is a main-sequence (hydrogen burning) star of spectral type A and luminosity class (five). These stars have spectra defined by strong hydrogen Balmer absorption lines. They measure between 1 ...
with a temperature of . It lies in the field of view of the
Kepler Mission
The Kepler space telescope is a defunct space telescope launched by NASA in 2009 to discover Earth-sized planets orbiting other stars. Named after astronomer Johannes Kepler, the spacecraft was launched into an Earth-trailing heliocentric orb ...
and was determined to have a companion object in orbit around it which is smaller and hotter than the main star.
KOI-74b
KOI-74b is a hot compact object orbiting KOI-74. It was discovered in 2010 by the
Kepler Mission
The Kepler space telescope is a defunct space telescope launched by NASA in 2009 to discover Earth-sized planets orbiting other stars. Named after astronomer Johannes Kepler, the spacecraft was launched into an Earth-trailing heliocentric orb ...
and came to attention because of its small size (its radius is only 4.3% of the
solar radius
Solar radius is a unit of distance used to express the size of objects in astronomy relative to the Sun. The solar radius is usually defined as the radius to the layer in the Sun's photosphere where the optical depth equals 2/3:
1\,R_ = 6.957 ...
) and high temperature of .
The orbit of KOI-74b around the main star takes 5.18875 days to complete. Analysis of relativistic boosting of light in the Kepler data indicates that it is likely to be a low mass
white dwarf
A white dwarf is a Compact star, stellar core remnant composed mostly of electron-degenerate matter. A white dwarf is very density, dense: in an Earth sized volume, it packs a mass that is comparable to the Sun. No nuclear fusion takes place i ...
of approximately 0.22 solar masses, resulting from an earlier phase of
mass transfer
Mass transfer is the net movement of mass from one location (usually meaning stream, phase, fraction, or component) to another. Mass transfer occurs in many processes, such as absorption, evaporation, drying, precipitation, membrane filtra ...
in a binary system when the object underwent its
giant phase.
See also
*
KOI-81, a similar system also discovered by the Kepler Mission.
*
Kepler Object of Interest, stars observed to have transits by the Kepler Mission
References
A-type main-sequence stars
Cygnus (constellation)
Eclipsing binaries
White dwarfs
74
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