K2-229

Last updated
K2-229
Observation data
Epoch J2000       Equinox J2000
Constellation Virgo
Right ascension 12h 27m 29.5848s [1]
Declination −06° 43 18.7660 [1]
Apparent magnitude  (V)10.985
Characteristics
Evolutionary stage Main sequence
Spectral type K2V [2]
Astrometry
Proper motion (μ)RA: −80.886±0.131 [1]   mas/yr
Dec.: 7.434±0.090 [1]   mas/yr
Parallax (π)9.7229 ± 0.1020  mas [1]
Distance 335 ± 4  ly
(103 ± 1  pc)
Details
Mass 0.837 +0.019
0.025
[2]   M
Radius 0.793 +0.032
0.020
[2]   R
Luminosity ~0.407 [3]   L
Surface gravity (log g)4.56 +0.03
0.05
[2]   cgs
Temperature 5185 ± 32 [2]   K
Metallicity [Fe/H]−0.06 ± 0.02 [2]   dex
Rotation 18.1 ± 0.3 days [2]
Rotational velocity (v sin i)2.4 ± 0.5 [2]  km/s
Age 5.4 +5.2
3.7
[2]   Gyr
Other designations
EPIC  228801451, TYC  4947-834-1, 2MASS J12272958-0643188
Database references
SIMBAD data

K2-229 (also designated EPIC 228801451 or TYC 4947-834-1) is a K-type main sequence star approximately 103 parsecs (335 light years) away in the constellation Virgo. It was observed by the Kepler Space Telescope during its K2 "Second Light" mission in Campaign 10.

Contents

Planetary system

As of March 27, 2018, K2-229 has a system of three confirmed exoplanets.

The K2-229 planetary system [2]
Companion
(in order from star)
Mass Semimajor axis
(AU)
Orbital period
(days)
Eccentricity Inclination Radius
b 2.59 (± 0.43)  M🜨 0.0128880.5842490 (assumed)83.9 ± 2.8° 1.165 +0.066
0.048
  R🜨
c<21.3  M🜨 0.075778.328340 (assumed)87.94 ± 0.18° 2.12 +0.11
0.08
  R🜨
d<25.1  M🜨 0.1820 ± 0.0004231.0 ± 1.10.39 ± 0.2988.92 ± 0.24° 2.64 ± 0.24  R🜨

All three known planets transit their star and would orbit inside that of Mercury if placed in the Solar System. Only the innermost has a well determined mass and composition.

K2-229b

K2-229b is a Super-Earth with an iron-rich composition. It is about 17% larger than Earth by radius, but is almost 2.6 times more massive. Its high density indicates it has a core-mass fraction of about 68%, nearly identical to that of Mercury. It is believed that like Mercury, the huge core of K2-229 is the result of a giant impact event. However, unlike Mercury, it orbits extremely close to its host star, with one orbit taking a little over 14 hours to complete. K2-229b has a temperature of over 1,960 K to 2,330 K, hot enough to melt iron and likely giving it an atmosphere of silicate vapor. [2]

K2-229c

K2-229c is a Mini-Neptune sized planet with a radius of 2.12 R🜨. Its mass has not been accurately determined, so only an upper limit of 21.3 ME can be given. However, a different method of radial velocity analysis gives the planet's mass at about 9.5 ME. With an orbital period of 8.32 days, K2-229c has an equilibrium temperature of 800 K (527 °C; 980 °F) and a dayside temperature of 962 K (689 °C; 1,272 °F). [2]

K2-229d

K2-229d is another Mini-Neptune with a radius of 2.64 R🜨, meaning it is likely gaseous. Only a maximum mass of 25.1 ME could be determined. The planet was detected by a single transit event lasting about two and a half hours long. There were two models for its orbital period: one where it took about 31 days to orbit and the second transit was during a large data gap; and another where it took over 50 days to orbit. The latter scenario was considered unlikely, as K2-229d would need to have a very eccentric orbit to exhibit such a short transit duration – so eccentric that its periapsis would cross the orbit of K2-229c and destabilize the system. It has an equilibrium temperature of 522 K (249 °C; 480 °F). [2]

See also

Related Research Articles

This page describes exoplanet orbital and physical parameters.

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Kepler-61b is a super-Earth exoplanet orbiting within parts of the habitable zone of the K-type main-sequence star Kepler-61. It is located about 1,100 light-years from Earth in the constellation of Cygnus. It was discovered in 2013 using the transit method, in which the dimming effect that a planet causes as it crosses in front of its star is measured, by NASA's Kepler spacecraft.

<span class="mw-page-title-main">HD 219134 b</span> Super-Earth orbiting HD 219134

HD 219134 b is one of at least five exoplanets orbiting HD 219134, a main-sequence star in the constellation of Cassiopeia. HD 219134 b has a size of about 1.6 R🜨, and a density of 6.4 g/cm3 and orbits at 21.25 light-years away. The exoplanet was initially detected by the instrument HARPS-N of the Italian Telescopio Nazionale Galileo via the radial velocity method and subsequently observed by the Spitzer telescope as transiting in front of its star. The exoplanet has a mass of about 4.5 times that of Earth and orbits its host star every three days. In 2017, it was found that the planet likely hosts an atmosphere.

HD 219134 c, also known as HR 8832 c, is a hot, dense, rocky exoplanet orbiting around the K-type star HD 219134 in the constellation of Cassiopeia. Originally thought to be a little less than three times the mass of Earth, it is now known to be over 4 times the mass and 51% larger in radius, suggesting a rocky composition with a higher quantity of iron than Earth. The exoplanet was initially detected by the instrument HARPS-N of the Italian Telescopio Nazionale Galileo via the radial velocity method. Transits of the planet were observed by the Spitzer Space Telescope in 2017. Later that year, it was predicted that HD 219134 c has an atmosphere.

HD 219134 d, also known as HR 8832 d, is an exoplanet orbiting around the K-type star HD 219134 in the constellation of Cassiopeia. It has a minimum mass over 16 times that of Earth, indicating that it is likely a Hot Neptune. The exoplanet was initially detected by the instrument HARPS-N of the Italian Telescopio Nazionale Galileo via the radial velocity method. Unlike HD 219134 b and HD 219134 c it was not observed by the Spitzer Space Telescope and thus its radius and density are unknown. Only a minimum possible radius can be given.

<span class="mw-page-title-main">K2-3d</span> Mini-Neptune orbiting K2-3

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Wolf 1061d is an exoplanet orbiting the red dwarf star Wolf 1061 in the Ophiuchus constellation, about 13.8 light years from Earth. It is the third and furthest planet in order from its host star in a triple planetary system, and has an orbital period of about 217 days.

<span class="mw-page-title-main">K2-33b</span> Young Super-Neptune orbiting K2-33

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<span class="mw-page-title-main">K2-72e</span> Goldilocks terrestrial exoplanet orbiting K2-72

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<span class="mw-page-title-main">LHS 1140 b</span> Super-Earth orbiting LHS 1140

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Kepler-277c 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).

K2-148b is a confirmed super-Earth, probably rocky, closely orbiting a small orange dwarf star. It is the innermost of three Super-Earths around the star K2-148, which is in a wide binary pair with the M0.5V red dwarf EPIC 220194953. K2-148b is the smallest planet of the system, at about a third larger than Earth, and could be terrestrial in nature. However, the three planets do not exhibit significant transit timing variations, implying that they could have relatively low masses. The planet was validated in early 2018 by Hirano et al. and is too hot for known life.

K2-141b is a massive rocky exoplanet orbiting extremely close to a K Type orange main-sequence star K2-141. The planet was first discovered by the Kepler space telescope during its K2 “Second Light” mission and later observed by the HARPS-N spectrograph. It is classified as an Ultra-short Period (USP) and is confirmed to be terrestrial in nature. Its high density implies a massive iron core taking up between 30% and 50% of the planet's total mass.

K2-229b is an extremely hot, solid, iron-rich exoplanet in a close orbit around the active K-dwarf K2-229 in the constellation Virgo, 335 light years away from Earth.

<span class="mw-page-title-main">K2-288Bb</span> Mini-Neptune orbiting K2-288B

K2-288Bb is a super-Earth or mini-Neptune exoplanet orbiting in the habitable zone of K2-288B, a low-mass M-dwarf star in a binary star system in the constellation of Taurus about 226 light-years from Earth. It was discovered by citizen scientists while analysing data from the Kepler spacecraft's K2 mission, and was announced on 7 January 2019. K2-288 is the third transiting planet system identified by the Exoplanet Explorers program, after the six planets of K2-138 and the three planets of K2-233.

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References

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  3. "HEC: Exoplanets Calculator - Planetary Habitability Laboratory @ UPR Arecibo". Archived from the original on 2019-06-02. Retrieved 2018-06-17.