K2-38b

K2-38b
Exoplanet List of exoplanets
Parent star
Star K2-38
Constellation Scorpius
Right ascension (α) 16h 00m 08.0615s[1]
Declination (δ) −23° 11′ 21.336″[1]
Apparent magnitude (mV) 11.39 [2]
Distanceapprox. 800[1] ly
(approx. 240[1] pc)
Spectral type G2 V
Mass (m) 1.07 (± 0.05)[3] M☉
Radius (r) 1.10 (± 0.09)[3] R☉
Temperature (T) 5757[3] K
Metallicity [Fe/H] +0.28 (± 0.04)[3]
Age unknown[3] Gyr
Physical characteristics
Mass(m)12.0 (± 2.9)[3] M⊕
Radius(r)1.55 (± 0.16)[3] R⊕
Density(ρ)17.5+8.5
−6.2[3] g cm−3
Surface gravity(g)4.99+2.72
−1.88 g
Temperature (T) 1,184 K (911 °C; 1,672 °F)[2]
Orbital elements
Semi-major axis(a) 0.0506 (± 0.0008)[3] AU
Eccentricity (e) null[3]
Orbital period(P) 4.01593 (± 0.0005)[3] d
Inclination (i) 87.28 +1.88
−3.08[3]°
Discovery information
Discovery date 2016
Discoverer(s)
Discovery method Transit
Discovery site Kepler Space Observatory
Discovery status Confirmed[2]
Database references
Extrasolar Planets
Encyclopaedia		data
SIMBADdata
Exoplanet Archivedata
Open Exoplanet Cataloguedata

K2-38b, also designated EPIC 204221263 b, is a massive rocky exoplanet closely orbiting a Sun-like star and is one of the densest planets ever found. Discovered in 2016 by Crossfield et al. and later characterized by Sinukoff et al., K2-38b is a rocky Super-Earth about 55% larger than Earth but about 12 times more massive, indicating a composition rich in iron and an extremely high surface gravity. The planet is within K2 Campaign 2, in the constellation Scorpius.

Characteristics

Mass, radius, and temperature

K2-38b is a massive rocky exoplanet significantly larger and more massive than Earth. It has a radius of 1.55 R⊕,[3] close to the 1.6 R⊕ limit where planets would begin to accumulate thick hydrogen-helium atmospheres and become something similar to a Mini-Neptune. However, K2-38b is instead a very dense terrestrial planet made almost entirely of iron,[2] with a mass of about 12.0 M⊕ and a density of about 17.5 g/cm3.[3] This makes it one of the densest exoplanets ever discovered. The planet has a surface gravity around 5 times that of Earth, about twice that of the planet Jupiter. K2-38b is also very hot, with an equilibrium temperature of 1,184 K (911 °C; 1,672 °F), hot enough to melt some types of metals.[2]

Orbit

K2-38b has a very tight orbit around its host star. The planet takes just 4 days to complete a single orbit at a distance of about 0.0506 AU. For comparison, Mercury orbits every 88 days at 0.38 AU from the Sun. The eccentricity of K2-38's orbit is unknown.[3]

Host star

The parent star K2-38 is a G2 V main-sequence star, similar to our own Sun. It is 1.10 R☉ and 1.07 M☉, with a temperature of 5757 K and an unknown age. For comparison, the Sun has a temperature of 5778 K and is about 4.5 billion years old.[3]

The visual magnitude of K2-38, or how bright it appears to the human eye, is 11.39. Therefore, it is far too dim to be seen without a telescope.[2]

See also

References

  1. 1 2 3 4 Brown, A. G. A; et al. (2016). "Gaia Data Release 1. Summary of the astrometric, photometric, and survey properties". Astronomy and Astrophysics. 595. A2. arXiv:1609.04172. Bibcode:2016A&A...595A...2G. doi:10.1051/0004-6361/201629512. Gaia Data Release 1 catalog entry
  2. 1 2 3 4 5 6 Sinukoff, Evan; Howard, Andrew W.; Petigura, Erik A.; Schlieder, Joshua E.; Crossfield, Ian J. M.; Ciardi, David R.; Fulton, Benjamin J.; Issacson, Howard; Aller, Kimberly M.; Baranec, Christoph; Beichman, Charles A.; Hansen, Brad M. S.; Knutson, Heather A.; Law, Nicholas M.; Liu, Michael C.; Riddle, Reed; Dressing, Courtney D. (21 June 2016). "Eleven Multi-planet Systems from K2 Campaigns 1 & 2 and the Masses of Two Hot Super-Earths". arXiv:1511.09213 [astro-ph.EP].
  3. 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 "K2-38 b CONFIRMED PLANET OVERVIEW PAGE". NASA Exoplanet Archive. Retrieved 2018-01-20.
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