GJ 9827 is a star in the constellation of Pisces. It is a K-type main-sequence star with an apparent magnitude of 10.250.[2] It is 97 light-years (30 parsecs) away, based on parallax.[1]
| Observation data Epoch J2000 Equinox J2000 | |
|---|---|
| Constellation | Pisces |
| Right ascension | 23h 27m 04.83769s[1] |
| Declination | −01° 17′ 10.5827″[1] |
| Apparent magnitude (V) | 10.250[2] |
| Characteristics | |
| Spectral type | K6 V[2] |
| B−V color index | +1.30[3] |
| Astrometry | |
| Radial velocity (Rv) | 32.01±0.27[1] km/s |
| Proper motion (μ) | RA: 375.977 mas/yr[1] Dec.: 215.870 mas/yr[1] |
| Parallax (π) | 33.7247 ± 0.0169 mas[1] |
| Distance | 96.71 ± 0.05 ly (29.65 ± 0.01 pc) |
| Details | |
| Mass | 0.606+0.015 −0.014[4] M☉ |
| Radius | 0.602+0.005 −0.004[4] R☉ |
| Luminosity | 0.119+0.035 −0.029[2] L☉ |
| Surface gravity (log g) | 4.682±0.021[5] cgs |
| Temperature | 4,236±12[6] K |
| Metallicity [Fe/H] | −0.29±0.03[6] dex |
| Rotation | 28.16+3.38 −2.66 d[6] |
| Rotational velocity (v sin i) | <1.75[6] km/s |
| Age | 10+3 −5[4] Gyr |
| Other designations | |
| Database references | |
| SIMBAD | data |
| ARICNS | data |
The rotation period of the star could not be determined as of 2020, and could be either around 15 or 30 days, depending on the interpretation of available data.[5]
Planetary system
editGJ 9827 has 3 transiting planets seen by the Kepler space observatory in their K2 survey. As of October 2017, it was the closest star discovered to have transiting exoplanets found by either the Kepler or K2 missions. The planets (b, c, d) have radii of 1.62, 1.27, and 2.09 times that of the Earth, and periods of 1.209, 3.648, and 6.201 days (ratios 1:3:5).[2] Because of its close distance the system is considered an excellent target for studying atmospherics of exoplanets.
In late 2017, the masses of all three planets were determined using the Planet Finder Spectrograph on the Magellan II Telescope. Planet b was found to be very iron-rich, planet c appears to be mainly rocky, and planet d is a typical volatile-rich planet. GJ 9827b is noted as being one of the densest planets yet found, with its mass containing about ≥50% iron.[2]
More precise radial velocity measurements released in late February 2018 revealed that all three planets have a lower density than Earth and have some amount of volatiles in their compositions. GJ 9827b and c are mainly rocky (containing less than 1% mass fraction of water, and negligible helium and hydrogen) with very thin volatile envelopes,[5] while GJ 9827d is more akin to a mini-Neptune. The loss of primordial atmosphere was indirectly confirmed in 2020, as no helium was detected at GJ 9827 d.[8] With a mass of about 1.5 ME, GJ 9827c is one of the least massive planets detected with radial velocity.[9] The atmospheres for GJ 9827b and GJ 9827d were not detected at all in 2021 observations.[10]
A 2023 study using the Hubble Space Telescope detected water vapor in the atmosphere of GJ 9827 d. This study describes the planet as a potential ocean world.[11][12]
A 2024 study used the Échelle SPectrograph for Rocky Exoplanets and Stable Spectroscopic Observations (ESPRESSO) of the European Southern Observatory to model the stellar activity of GJ 9827 and derive masses, orbital periods and radial velocity amplitudes of planets b, c, and d.[6]
| Companion (in order from star) |
Mass | Semimajor axis (AU) |
Orbital period (days) |
Eccentricity | Inclination | Radius |
|---|---|---|---|---|---|---|
| b | 4.28+0.35 −0.33 M🜨 |
0.0189(4) | 1.208974(1) | <0.063 | 87.60+1.31 −1.27° |
1.44+0.09 −0.07 R🜨 |
| c | 1.86+0.37 −0.39 M🜨 |
0.0395(9) | 3.648103(13) | <0.094 | 89.09+0.60 −0.68° |
1.13+0.07 −0.05 R🜨 |
| d | 3.02+0.58 −0.57 M🜨 |
0.0563(12) | 6.201812(9) | <0.13 | 87.66+0.13 −0.16° |
1.89+0.16 −0.14 R🜨 |
References
edit- ^ a b c d e f Vallenari, A.; et al. (Gaia collaboration) (2023). "Gaia Data 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. S2CID 244398875. Gaia DR3 record for this source at VizieR.
- ^ a b c d e f Rodriguez, Joseph E; Vanderburg, Andrew; Eastman, Jason D; Mann, Andrew W; Crossfield, Ian J. M; Ciardi, David R; Latham, David W; Quinn, Samuel N (2018). "A System of Three Super Earths Transiting the Late K-Dwarf GJ 9827 at 30 pc". The Astronomical Journal. 155 (2): 72. arXiv:1709.01957. Bibcode:2018AJ....155...72R. doi:10.3847/1538-3881/aaa292. S2CID 55459523.
- ^ Mumford, G. S. (1956). "Photoelectric observations of red dwarf stars". Astronomical Journal. 61: 213–218. Bibcode:1956AJ.....61..213M. doi:10.1086/107329.
- ^ a b c d Bonomo, A. S.; Dumusque, X.; et al. (April 2023). "Cold Jupiters and improved masses in 38 Kepler and K2 small-planet systems from 3661 high-precision HARPS-N radial velocities. No excess of cold Jupiters in small-planet systems". Astronomy & Astrophysics. 677: A33. arXiv:2304.05773. Bibcode:2023A&A...677A..33B. doi:10.1051/0004-6361/202346211. S2CID 261556620.
- ^ a b c Kosiarek, Molly R.; et al. (2020). "Physical Parameters of the Multi-Planet Systems HD 106315 and GJ 9827". The Astronomical Journal. 161 (1): 47. arXiv:2009.03398. Bibcode:2021AJ....161...47K. doi:10.3847/1538-3881/abca39. S2CID 221534625.
- ^ a b c d e f Passegger, V. M.; Suárez Mascareño, A.; et al. (April 2024). "The compact multi-planet system GJ 9827 revisited with ESPRESSO". Astronomy and Astrophysics. 684: A22. arXiv:2401.06276. Bibcode:2024A&A...684A..22P. doi:10.1051/0004-6361/202348592.
- ^ "BD-02 5958". SIMBAD. Centre de données astronomiques de Strasbourg. Retrieved 8 October 2017.
- ^ Kasper, David; Bean, Jacob L.; Oklopčić, Antonija; Malsky, Isaac; Kempton, Eliza M.-R.; Désert, Jean-Michel; Rogers, Leslie A.; Mansfield, Megan (2020). "Non-detection of Helium in the Upper Atmospheres of Three Sub-Neptune Exoplanets". The Astronomical Journal. 160 (6): 258. arXiv:2007.12968. Bibcode:2020AJ....160..258K. doi:10.3847/1538-3881/abbee6. S2CID 220793801.
- ^ Prieto-Arranz, J.; et al. (2018). "Mass determination of the 1:3:5 near-resonant planets transiting GJ 9827 (K2-135)". Astronomy and Astrophysics. 618. A116. arXiv:1802.09557. Bibcode:2018A&A...618A.116P. doi:10.1051/0004-6361/201832872. S2CID 119379575.
- ^ Carleo, Ilaria; Youngblood, Allison; Redfield, Seth; Barris, Nuria Casasayas; Ayres, Thomas R.; Vannier, Hunter; Fossati, Luca; Palle, Enric; Livingston, John H.; Lanza, Antonino F.; Niraula, Prajwal; Alvarado-Gómez, Julián D.; Chen, Guo; Gandolfi, Davide; Guenther, Eike W.; Linsky, Jeffrey L.; Nagel, Evangelos; Narita, Norio; Nortmann, Lisa; Shkolnik, Evgenya L.; Stangret, Monika (2021), "A Multiwavelength Look at the GJ 9827 System: No Evidence of Extended Atmospheres in GJ 9827b and d from HST and CARMENES Data", The Astronomical Journal, 161 (3): 136, arXiv:2101.06277, Bibcode:2021AJ....161..136C, doi:10.3847/1538-3881/abdb2f, S2CID 231632288
- ^ Roy, Pierre-Alexis; Benneke, Björn; et al. (September 2023). "Water Absorption in the Transmission Spectrum of the Water World Candidate GJ 9827 d". The Astrophysical Journal Letters. 954 (2): L52. arXiv:2309.10845. Bibcode:2023ApJ...954L..52R. doi:10.3847/2041-8213/acebf0.
- ^ Ritika (26 January 2024). "Water Vapour Found On Distant Exoplanet By NASA's Hubble Telescope - According to the space agency, the Hubble program has observed that the planet GJ 9827d during 11 transits were spaced out over a span of three years". NDTV World. Archived from the original on 27 January 2024. Retrieved 26 January 2024.
External links
edit- Abrar, Umer (28 September 2017). "Kepler Space Telescope Just Discovered One Of The Most Important Planet Yet". The Space Academy.