Kepler-277c

Kepler-277c
Exoplanet List of exoplanets
Parent star
Star Kepler-277
Constellation Lyra
Right ascension (α) 19h 06m 19.96s[1]
Declination (δ) +39° 04′ 38.0″[1]
Apparent magnitude (mV) unknown
Spectral type unknown
Mass (m) 1.12 +0.19
−0.11[1] M☉
Radius (r) 1.69 +0.42
−0.36[1] R☉
Temperature (T) 5946[1] K
Metallicity [Fe/H] -0.315[1]
Physical characteristics
Mass(m)64.2 +18.1
−15.7[1][2] M⊕
Radius(r)3.36 +0.83
−0.72[1] R⊕
Density(ρ)9.33+15.33
−5.69 g cm−3
Surface gravity(g)5.69+6.12
−2.93 g
Temperature (T) 745 K (472 °C; 881 °F)[3]
Orbital elements
Semi-major axis(a) ~0.209 AU
Eccentricity (e) null[1]
Orbital period(P) 33.006[1] d
Inclination (i) null[1]°
Discovery information
Discovery date 2014
Discoverer(s)
Discovery method Transit
Discovery site Kepler Space Observatory
Discovery status Confirmed
Database references
Extrasolar Planets
Encyclopaedia		data
SIMBADdata
Exoplanet Archivedata
Open Exoplanet Cataloguedata

Kepler-277c (also known by its Kepler Objects of Interest designation KOI-1215.02) is the third most massive and second-largest rocky planet ever discovered, with a mass about 64 times that of Earth. Discovered in 2014 by the Kepler Space Telescope, Kepler-277c is a Neptune-sized exoplanet 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, the planet's mass was determined using transit-timing variations (TTVs).

Characteristics

Mass, Radius, 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 R⊕, close to the size of Neptune. 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 M⊕[1], close to Saturn's mass at 95.16 M⊕. 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[2]. It is currently the third most massive and second largest terrestrial planet ever discovered, behind Kepler-277b in mass[4] and PSR J1719-1438 b in both radius and mass[5]. Due to its proximity to its host star, Kepler-277c is quite hot with an equilibrium temperature of about 745 K (472 °C; 881 °F)[3], hot enough to melt certain metals.

Orbit

Kepler-277c orbits close to its host star, with one orbit lasting 33.006 days[1]. Its semi-major axis, or average distance from the parent object, is about 0.209 AU. For comparison, the planet Mercury 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.

Host star

The parent star Kepler-277 is a large yellow star. It is 1.69 R☉ and 1.12 M☉, with a temperature of 5946 K, a metallicity of -0.315 [Fe/H], and an unknown age[1]. For comparison, the Sun has a temperature of 5778 K, a metallicity of 0.00 [Fe/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 star.

See also

References

  1. 1 2 3 4 5 6 7 8 9 10 11 12 13 14 "Kepler-277 c CONFIRMED PLANET OVERVIEW PAGE". NASA Exoplanet Archive. Retrieved 2018-01-20.
  2. 1 2 Xie, Ji-Wei (7 January 2014). "Transit Timing Variations of Near-Resonance Planetary Pairs. II. Confirmation of 30 planets in 15 Multiple Planet Systems". arXiv:1309.2329 [astro-ph.EP].
  3. 1 2 PHL's calculators
  4. ↑ https://exoplanetarchive.ipac.caltech.edu/cgi-bin/DisplayOverview/nph-DisplayOverview?objname=Kepler-277+b&type=CONFIRMED_PLANET
  5. ↑ http://www.manchester.ac.uk/discover/news/a-planet-made-of-diamond/
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