Observation data Epoch J2000 Equinox J2000 | |
---|---|
Constellation | Aquarius [1] |
Right ascension | 22h 22m 29.8611s [2] |
Declination | −07° 57′ 19.853″ [2] |
Apparent magnitude (V) | 16.06 [3] |
Characteristics | |
Spectral type | M4V [4] [5] |
Apparent magnitude (J) | 11.695±0.030 [6] |
Apparent magnitude (H) | 11.028±0.023 [6] |
Apparent magnitude (K) | 10.746±0.023 [6] |
Variable type | Planetary transit variable [4] |
Astrometry | |
Radial velocity (Rv) | 11.7 [5] km/s |
Proper motion (μ) |
RA: −254.604(41)
[2]
mas/
yr Dec.: −194.554(30) [2] mas/ yr |
Parallax (π) | 15.8734 ± 0.0343 mas [2] |
Distance | 205.5 ± 0.4
ly (63.0 ± 0.1 pc) |
Details [4] | |
Mass | 0.257±0.048 M☉ |
Radius | 0.288±0.028 R☉ |
Surface gravity (log g) | 4.93±0.04 cgs |
Temperature | 3214±60 K |
Metallicity [Fe/H] | 0.26±0.10 dex |
Other designations | |
Database references | |
SIMBAD | data |
K2-28 is a metal rich M4-type main sequence star. One confirmed transiting exoplanet is known to orbit this star. There is another star 5.2 arcseconds to the north–east of K2-28. However, this star has a different proper motion, and is therefore physically unrelated and probably a background star. [4]
K2-28b was first noticed as a candidate extrasolar planet by Vanderburg et al. in 2016, who, in a search of 59,174 stars from the Kepler space telescope's first year of K2 observations, found 234 planetary candidates. [8] Shortly thereafter the K2-ESPRINT Project confirmed that the candidate was a super-Earth sized planet in a close orbit around a red dwarf star. [4]
K2-28b is a sub-Neptune sized planet orbiting its star in only 2.26 days. Despite its short orbital period the equilibrium temperature of the planet is a relatively low 500 Kelvin due to the low luminosity of the parent star. [4] Because of the very small size of the parent star, this planet is a particularly favorable target for transmission spectroscopy by the James Webb Space Telescope, which should be able to determine if the atmosphere is cloudy or clear by observing roughly 5 transits. [9] Among a group of small and cool planets orbiting relatively bright M-dwarfs, its predicted secondary eclipse depth of 230 parts-per-million is second only to Gliese 1214 b. [3]
Companion (in order from star) |
Mass |
Semimajor axis ( AU) |
Orbital period ( days) |
Eccentricity | Inclination | Radius |
---|---|---|---|---|---|---|
K2-28b | 7.18+5.92 −3.08 (estimate) M🜨 |
0.0191+0.0037 −0.0029 |
2.2604455±0.0000010 | 0 | 87.1+0.90 −0.74 ° |
2.56+0.27 −0.26 R🜨 |
Observation data Epoch J2000 Equinox J2000 | |
---|---|
Constellation | Aquarius [1] |
Right ascension | 22h 22m 29.8611s [2] |
Declination | −07° 57′ 19.853″ [2] |
Apparent magnitude (V) | 16.06 [3] |
Characteristics | |
Spectral type | M4V [4] [5] |
Apparent magnitude (J) | 11.695±0.030 [6] |
Apparent magnitude (H) | 11.028±0.023 [6] |
Apparent magnitude (K) | 10.746±0.023 [6] |
Variable type | Planetary transit variable [4] |
Astrometry | |
Radial velocity (Rv) | 11.7 [5] km/s |
Proper motion (μ) |
RA: −254.604(41)
[2]
mas/
yr Dec.: −194.554(30) [2] mas/ yr |
Parallax (π) | 15.8734 ± 0.0343 mas [2] |
Distance | 205.5 ± 0.4
ly (63.0 ± 0.1 pc) |
Details [4] | |
Mass | 0.257±0.048 M☉ |
Radius | 0.288±0.028 R☉ |
Surface gravity (log g) | 4.93±0.04 cgs |
Temperature | 3214±60 K |
Metallicity [Fe/H] | 0.26±0.10 dex |
Other designations | |
Database references | |
SIMBAD | data |
K2-28 is a metal rich M4-type main sequence star. One confirmed transiting exoplanet is known to orbit this star. There is another star 5.2 arcseconds to the north–east of K2-28. However, this star has a different proper motion, and is therefore physically unrelated and probably a background star. [4]
K2-28b was first noticed as a candidate extrasolar planet by Vanderburg et al. in 2016, who, in a search of 59,174 stars from the Kepler space telescope's first year of K2 observations, found 234 planetary candidates. [8] Shortly thereafter the K2-ESPRINT Project confirmed that the candidate was a super-Earth sized planet in a close orbit around a red dwarf star. [4]
K2-28b is a sub-Neptune sized planet orbiting its star in only 2.26 days. Despite its short orbital period the equilibrium temperature of the planet is a relatively low 500 Kelvin due to the low luminosity of the parent star. [4] Because of the very small size of the parent star, this planet is a particularly favorable target for transmission spectroscopy by the James Webb Space Telescope, which should be able to determine if the atmosphere is cloudy or clear by observing roughly 5 transits. [9] Among a group of small and cool planets orbiting relatively bright M-dwarfs, its predicted secondary eclipse depth of 230 parts-per-million is second only to Gliese 1214 b. [3]
Companion (in order from star) |
Mass |
Semimajor axis ( AU) |
Orbital period ( days) |
Eccentricity | Inclination | Radius |
---|---|---|---|---|---|---|
K2-28b | 7.18+5.92 −3.08 (estimate) M🜨 |
0.0191+0.0037 −0.0029 |
2.2604455±0.0000010 | 0 | 87.1+0.90 −0.74 ° |
2.56+0.27 −0.26 R🜨 |