Kepler-277c (also known by its Kepler Objects of Interest designation KOI-1215.02) is the third most massive and second-largest

rocky ''Rocky'' is a 1976 American sports drama film directed by John G. Avildsen and written by and starring Sylvester Stallone. It is the first installment in the ''Rocky'' franchise and stars Talia Shire, Burt Young, Carl Weathers, and Burgess M ...

planet ever discovered, with a mass about 64 times that of

Earth Earth is the third planet from the Sun and the only astronomical object known to harbor life. While large volumes of water can be found throughout the Solar System, only Earth sustains liquid surface water. About 71% of Earth's surfa ...

. Discovered in 2014 by the

Kepler Space Telescope The Kepler space telescope is a disused 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 ...

, Kepler-277c is a Neptune-sized

exoplanet An exoplanet or extrasolar planet is a planet outside the Solar System. The first possible evidence of an exoplanet was noted in 1917 but was not recognized as such. The first confirmation of detection occurred in 1992. A different planet, init ...

with a very high mass and density for an object of its radius, suggesting a composition made mainly of rock with some amounts of water. Along with its sister planet,

Kepler-277b Kepler-277b (also known by its Kepler Objects of Interest designation KOI-1215.01) is the second most massive and third-largest rocky planet ever discovered, with a mass close to that of Saturn. Discovered in 2014 by the Kepler Space Telescope, Kep ...

, the planet's mass was determined using transit-timing variations (TTVs).

Characteristics

Size and temperature

Kepler-277c was detected using the transit method and TTVs, allowing for both its mass and radius to be determined to some level. It is approximately 3.36 , close to the size of

Neptune Neptune is the eighth planet from the Sun and the farthest known planet in the Solar System. It is the fourth-largest planet in the Solar System by diameter, the third-most-massive planet, and the densest giant planet. It is 17 times ...

. At that radius, most planets should be gaseous Mini-Neptunes with no solid surface. However, the mass of Kepler-277c is extremely high for its size. Transit-timing variations indicate a planetary mass of about 64.2 , close to Saturn's mass at 95.16 . The planet has a density of approximately 9.33 g/cm³ and about 5.7 times the surface gravity of Earth. Such a high density for an object of this size implies that, like its sister planet, Kepler-277c is an enormous rock-based planet with a small portion of its mass as water. It is currently the third most massive and second largest terrestrial planet ever discovered, behind Kepler-277b in mass and

PSR J1719-1438 b PSR may refer to: Organizations * Pacific School of Religion, Berkeley, California, US * Palestinian Center for Policy and Survey Research * Physicians for Social Responsibility, US ;Political parties: * Revolutionary Socialist Party (Portuga ...

in both radius and mass. Due to its proximity to its host star, Kepler-277c is quite hot with an equilibrium temperature of about , hot enough to melt certain metals.

Orbit

Kepler-277c orbits close to its host star, with one orbit lasting 33.006 days. Its semi-major axis, or average distance from the parent object, is about 0.209 AU. For comparison, the planet

Mercury Mercury commonly refers to: * Mercury (planet), the nearest planet to the Sun * Mercury (element), a metallic chemical element with the symbol Hg * Mercury (mythology), a Roman god Mercury or The Mercury may also refer to: Companies * Merc ...

in our Solar System takes 88 days to orbit at a distance of 0.38 AU. At this distance, Kepler-277c is very hot and most likely tidally locked to its host star. It is close to a 2:1 resonance with Kepler-277b, which orbits at an average distance of about 0.136 AU.

Host star

The parent star Kepler-277 is a large yellow star. It is 1.69 and 1.12 , with a temperature of 5946 K, a metallicity of -0.315 e/H and an unknown age. For comparison, the Sun has a temperature of 5778 K, a metallicity of 0.00 e/H and an age of about 4.5 billion years. The large radius in comparison to its mass and temperature suggest that Kepler-277 could be a

Subgiant A subgiant is a star that is brighter than a normal main-sequence star of the same spectral class, but not as bright as giant stars. The term subgiant is applied both to a particular spectral luminosity class and to a stage in the evolution of ...

star.

References

{{Lyra Exoplanets discovered in 2014 Transiting exoplanets Exoplanets discovered by the Kepler space telescope Lyra (constellation) Mega-Earths

Characteristics

Size and temperature

Orbit

Host star

See also

References