K2-72
| Observation data EpochJ2000EquinoxJ2000 | |
|---|---|
| Constellation | Aquarius |
| Right ascension | 22h18m29.25485s[1] |
| Declination | −09° 36′ 44.3811″[1] |
| Characteristics | |
| Spectral type | M2.7 V[citation needed] |
| Astrometry | |
| Radial velocity(Rv) | −42.92±3.35[1]km/s |
| Proper motion(μ) | RA:195.834mas/yr[1] Dec.:74.259mas/yr[1] |
| Parallax(π) | 15.0346 ± 0.0277mas[1] |
| Distance | 216.9 ± 0.4ly (66.5 ± 0.1pc) |
| Details | |
| Mass | 0.27+0.08 −0.09[2]M☉ |
| Radius | 0.33±0.03[2]R☉ |
| Surface gravity(logg) | 4.831963±0.152cgs |
| Temperature | 3360+87 −86[2]K |
| Other designations | |
| Database references | |
| SIMBAD | data |
K2-72(also designatedEPIC 206209135) is a coolred dwarfstarof spectral class M2.7V located about 217light-years(67parsecs) away from the Earth in the constellation ofAquarius.It is known to host four planets, all similar in size to Earth, with one of them residing within thehabitable zone.
Nomenclature and history
[edit]K2-72 also has the2MASScatalogue number J22182923-0936444. Its EPIC (Ecliptic Plane Input Catalog) number is 206209135.
The star's planetary companions were discovered byNASA'sKepler Mission,a mission tasked with discovering planets intransitaround their stars. The transit method that Kepler uses involves detecting dips in brightness in stars. These dips in brightness can be interpreted as planets whose orbits move in front of their stars from the perspective ofEarth.The name K2-72 derives directly from the fact that the star is the catalogued 72nd star discovered by theK2mission to have confirmed planets.
The designationb,c,d,andederives from the order of discovery. The designation ofbis given to the first planet orbiting a given star, andeto the last.[3]In the case of K2-72, there were four planets, so only lettersbtoeare used. At first the planets were all thought to be smaller than Earth. However, in 2017, new analysis by Martinezet al.and Courtney Dressing found that K2-72 was significantly larger than previous estimates, and found that the planets were all larger than Earth, although all are still expected to be rocky.
Stellar characteristics
[edit]K2-72 is aM-typestar that is approximately 27% the mass of and 33% the radius of theSun,according to the analysis done by Dressinget al.The results found by Martinezet al.suggest a larger star, with about 36% the radius and mass of the Sun. Both give a luminosity estimate between 0.013 and 0.015 solar luminosities. It has a surface temperature of between 3360 and 3370Kand its age is unknown. In comparison, the Sun is about 4.6 billion years old[4]and has a surface temperature of 5778 K.[5]
The star'sapparent magnitude,or how bright it appears from Earth's perspective, is 15.309. Therefore, it is too dim to be seen with the naked eye and can only be observed with a telescope.
Planetary system
[edit]The star is known to host four planets, all likely to be rocky. Only one (K2-72e) is currently known to reside inside the habitable zone, although K2-72c may straddle the inner edge.
| Companion (in order from star) |
Mass | Semimajor axis (AU) |
Orbital period (days) |
Eccentricity | Inclination | Radius |
|---|---|---|---|---|---|---|
| b | — | 0.040+0.004 −0.005 |
5.577212+0.000417 −0.000419 |
0.110000+0.196982 −0.087659 |
89.15+0.59 −0.86° |
1.08±0.11R🜨 |
| d | — | 0.050+0.004 −0.006 |
7.760178±0.001496 | 0.110000+0.207832 −0.092330 |
89.26+0.50 −0.69° |
1.16±0.13R🜨 |
| c | — | 0.078+0.007 −0.01 |
15.189034+0.003128 −0.003149 |
0.110000+0.201970 −0.091536 |
89.54+0.32 −0.44° |
1.01±0.12R🜨 |
| e | — | 0.106+0.009 −0.013 |
24.158868+0.003726 −0.003850 |
0.110000+0.198676 −0.086832 |
89.68+0.22 −0.32° |
1.29+0.14 −0.13R🜨 |
References
[edit]- ^abcdeVallenari, A.; et al. (Gaia collaboration) (2023)."GaiaData Release 3. Summary of the content and survey properties ".Astronomy and Astrophysics.674:A1.arXiv:2208.00211.Bibcode:2023A&A...674A...1G.doi:10.1051/0004-6361/202243940.S2CID244398875. Gaia DR3 record for this sourceatVizieR.
- ^abcd"NASA Exoplanet Archive".NASA Exoplanet Science Institute.14 October 2020.Retrieved2020-10-13.
- ^Hessman, F. V.; Dhillon, V. S.; Winget, D. E.; Schreiber, M. R.; Horne, K.; Marsh, T. R.; Guenther, E.; Schwope, A.; Heber, U. (2010). "On the naming convention used for multiple star systems and extrasolar planets".arXiv:1012.0707[astro-ph.SR].
- ^Fraser Cain (16 September 2008)."How Old is the Sun?".Universe Today.Retrieved19 February2011.
- ^Fraser Cain (15 September 2008)."Temperature of the Sun".Universe Today.Retrieved19 February2011.
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