K2-25
Red dwarf star located in the Hyades cluster
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K2-25 is a young red dwarf star located in the Hyades cluster. There is a single known Neptune-sized planet in a 3.5 day orbit.
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Location of K2-25 in the Hyades cluster | |
| Observation data Epoch J2000 Equinox J2000 | |
|---|---|
| Constellation | Taurus[1] |
| Right ascension | 04h 13m 05.6131s[2] |
| Declination | +15° 14′ 52.018″[2] |
| Apparent magnitude (V) | 15.881[3] |
| Characteristics | |
| Evolutionary stage | main sequence[4] |
| Spectral type | M4.5 V[5] |
| Apparent magnitude (J) | 11.303(21)[6] |
| Apparent magnitude (H) | 10.732(20)[6] |
| Apparent magnitude (K) | 10.444(19)[6] |
| Variable type | Planetary transit[5] |
| Astrometry | |
| Radial velocity (Rv) | 38.64(15)[5] km/s |
| Proper motion (μ) | RA: 122.450(38) mas/yr[2] Dec.: −18.603(26) mas/yr[2] |
| Parallax (π) | 22.3572±0.0308 mas[2] |
| Distance | 145.9 ± 0.2 ly (44.73 ± 0.06 pc) |
| Details | |
| Mass | 0.2634(77)[7] M☉ |
| Radius | 0.2932(93)[7] R☉ |
| Luminosity | 0.00816(29)[7] L☉ |
| Temperature | 3207(58)[7] K |
| Metallicity [Fe/H] | 0.15(3)[5] dex |
| Rotation | 1.87708(66) d[4] |
| Rotational velocity (v sin i) | 7.71(29)[8] km/s |
| Age | 650(70)[8][9] Myr |
| Other designations | |
| vA 50, HAN 87, EPIC 210490365, 2MASS J04130560+1514520, Gaia DR3 3311804515502788352[10][11] | |
| Database references | |
| SIMBAD | data |
| Exoplanet Archive | data |
Hyades cluster
Using proper motion measurements in a search for low-luminosity members of the Hyades cluster, William van Altena first identified the star vA 50 (later known as K2-25) as a probable cluster member.[12] Membership in the Hyades cluster was later confirmed.[13][14][5]
Properties
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K2-25 is a red dwarf that is only 26% the mass of the Sun and less than 1% of the luminosity.[7] As a member of the Hyades cluster, it is only 650 million years old as compared to the Sun's 4.5 billion.[8]
There is clear evidence for starspot activity in both the Kepler data and radial velocities as well as the associated activity indicators.[15]
Planetary system
The star has one known planet, K2-25b, with searches of the Kepler space telescope data for transits of additional planets being negative.[5] Analysis of transit-timing variations from the Spitzer Space Telescope as well as the MEarth Project also found no evidence of additional planets.[16]
Discovery
Brightness measurements of K2-25 taken by the Kepler space telescope during its extended K2 mission led to the discovery of the transiting planet K2-25b.[5][10]
Characteristics
K2-25b is a Hot Neptune type planet in an eccentric 3.48 day orbit.[15]
Due to its proximity and the activity levels of its host star, K2-25b should be losing some of its atmosphere to space; however, observations of two transits by the Hubble Space Telescope to search for escaping neutral hydrogen were negative.[17]
| Companion (in order from star) |
Mass | Semimajor axis (AU) |
Orbital period (days) |
Eccentricity | Inclination | Radius |
|---|---|---|---|---|---|---|
| K2-25b | 24.5+5.7 −5.2 M🜨 |
0.0287(12) | 3.48456408+0.0000006 −0.0000005 |
0.428+0.050 −0.049 |
88.16+0.18 −0.21° |
3.44(12) R🜨 |