K2-3d

K2-3d
Exoplanet List of exoplanets

Size comparison between K2-3d (right) and the Earth.
Parent star
Star K2-3
Constellation Leo
Right ascension (α) 11h 29m 20.39s [1]
Declination (δ) −01° 27′ 17.2″[1]
Distance137 (± 6.5) ly
(42 (± 2)[1] pc)
Spectral type M0V
Mass (m) 0.612 (± 0.086)[1] M☉
Radius (r) 0.553 (± 0.041)[1] R☉
Temperature (T) 3896[2] K
Metallicity [Fe/H] −0.32 (± 0.13)[2]
Age <1[2] Gyr
Physical characteristics
Mass(m)7.50 (± 3.00)[1] M⊕
Radius(r)1.61 (±0.20)[1] R⊕
Stellar flux(F⊙)1.46 ⊕
Density(ρ)11.7 (±6.7)[1] g cm−3
Temperature (T) 300 K (27 °C; 80 °F)
Orbital elements
Semi-major axis(a) 0.2086 (± 0.0100)[1] AU
Eccentricity (e) 0.045 (± 0.045)[1]
Orbital period(P) 44.5705 (± 0.0059)[1] d
Inclination (i) 89.79 (± 0.15)[1]°
Discovery information
Discovery date 2015
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

K2-3d, also known as EPIC 201367065 d, is a confirmed massive solid exoplanet orbiting the red dwarf star K2-3, and the outermost of three such planets discovered in the system. It is located 137 light-years (42 pc) away from Earth in the constellation of Leo.[1][1][2] The exoplanet was found by using the transit method, in which the dimming effect that a planet causes as it crosses in front of its star is measured. It was the first planet in the Kepler "Second Light" mission to receive the letter "d" designation for a planet. Its discovery was announced in January 2015.[3]

Characteristics

Mass, radius, density and temperature

K2-3d is a super-Earth, meaning it has a mass and radius bigger than Earth's, but smaller than that of the ice giants Uranus and Neptune. It has a surface temperature of 280 K (7 °C; 44 °F) and a radius of 1.61 R⊕. Normally, a planet of this size would be a mini-Neptune, with no solid surface.[4] However, its unusual density when fit for a radius of K2-3d's size would make it an exception to this rule, giving it a solid surface: its density is 11.7±6.7 g/cm3.[1] This is far greater than the density of iron. Because of this, a composition of almost pure iron with some silicate (rocky) mixed in is likely, giving it a mass of around 7.5 M⊕.[1] For it to be completely iron, it would have to be 14 times more massive than Earth; however, this is unlikely.

Host star

The planet orbits a (M-type) red dwarf star named K2-3, orbited by a total of three known planets, of which K2-3d has the longest orbital period.[3] The star has a mass of 0.60 M☉ and a radius of 0.56 R☉.[2][3] It has a temperature of 3896 K and is about 1 billion years old.[2] In comparison, the Sun is 4.6 billion years old[5] and has a surface temperature of 5778 K.[6]

The star's apparent magnitude, or how bright it appears from Earth's perspective, is 12.17. Therefore, it is too dim to be seen with the naked eye.

Orbital statistics

K2-3d orbits its host star, which has about 6% of the Sun's luminosity, with an orbital period of 44 days and an orbital radius of about 0.2 times that of Earth (compared to the distance of Mercury from the Sun, which is about 0.38 AU).[2]

Habitability

The planet orbits on the edge of the inner (empirical) habitable zone, a region where, with the proper atmospheric properties and pressure, liquid water may exist on the surface of the planet. However, it is very likely tidally locked to its star, with one side facing towards its star in scorching heat, and the opposite side in bitter darkness.[7] Despite this, there is an area – the terminator line – where the surface temperatures may be comfortable enough to support liquid water. However, given that most models of the habitable zone parameters put K2-3d slightly beyond the inner edge of the habitable zone, it is likely to be too hot even at the terminator line and thus not habitable at all. Plus, the high gravity caused by the density of K2-3d would further hinder its habitability. Also, the stellar flux for the planet is an abnormally high 1.4 times that of Earth,[3] which could result in surface temperatures of up to 400–500 K (127–227 °C; 260–440 °F) because of a runaway greenhouse effect.

Discovery

The planet, along with the other two known planets in the K2-3 system, was announced in early January 2015 as part of the first results from the second mission of the Kepler spacecraft. With this, it was the first multiplanetary system of the mission as well.[3]

See also

References

  1. 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 "K2-3 d CONFIRMED PLANET OVERVIEW PAGE". NASA Exoplanet Archive. Retrieved 2015-10-17.
  2. 1 2 3 4 5 6 7 "The Extrasolar Planet Encyclopaedia — K2-3 d".
  3. 1 2 3 4 5 Crossfield, Ian J. M.; et al. (16 January 2015). "A NEARBY M STAR WITH THREE TRANSITING SUPER-EARTHS DISCOVERED BY K2". arXiv:1501.03798Freely accessible.
  4. ↑ "Most 1.6 Earth-radius planets are not rocky". 31 July 2014.
  5. ↑ Fraser Cain (16 September 2008). "How Old is the Sun?". Universe Today. Retrieved 19 February 2011.
  6. ↑ Fraser Cain (15 September 2008). "Temperature of the Sun". Universe Today. Retrieved 19 February 2011.
  7. ↑ http://www.hpcf.upr.edu/~abel/phl/hec_plots/hec_orbit/hec_orbit_K2-3_d.png

Coordinates: 11h 29m 20.39s, −01° 27′ 17.2″

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