TOI-6894
| Observation data Epoch J2000 Equinox J2000 | |
|---|---|
| Constellation | Leo[1] |
| Right ascension | 11h 33m 52.74948s[2] |
| Declination | +12° 27′ 30.5817″[2] |
| Apparent magnitude (V) | 18.22[3] |
| Characteristics | |
| Evolutionary stage | Red dwarf[4] |
| Spectral type | M5.0±0.5[4] |
| Apparent magnitude (J) | 13.169±0.023[5] |
| Apparent magnitude (H) | 12.486±0.022[5] |
| Apparent magnitude (K) | 12.207±0.021[5] |
| Apparent magnitude (TESS) | 14.905±0.008[6] |
| Astrometry | |
| Proper motion (μ) | RA: −146.897 mas/yr[2] Dec.: +22.227 mas/yr[2] |
| Parallax (π) | 13.6842±0.0532 mas[2] |
| Distance | 238.3 ± 0.9 ly (73.1 ± 0.3 pc) |
| Details[4] | |
| Mass | 0.207±0.011 M☉ |
| Radius | 0.2276±0.0057 R☉ |
| Luminosity | 0.00375±0.00033 L☉ |
| Surface gravity (log g) | 5.039±0.011 cgs |
| Temperature | 3,007±58 K |
| Metallicity [Fe/H] | 0.142±0.087 dex |
| Other designations | |
| TIC 67512645, 2MASS J11335277+1227034[7] | |
| Database references | |
| SIMBAD | data |
TOI-6894 is a star in the constellation Leo. Its apparent magnitude of 18.22[3] is below naked eye vision. Based on parallax measurements, it lies at a distance of 238 light-years (73 parsecs).[2] The star was first described in 2003 by the 2MASS survey,[5] and was analysed by the TESS satellite in search for transiting exoplanets.[8]
This is a red dwarf of spectral class M5.0. It has 0.207 times the Sun's mass, 0.2276 times the Sun's radius, and a mere 0.38% of the solar luminosity. Its effective temperature of 3,000 K give it a typical hue. The iron-to-hydrogen abundance ratio, a metallicity indicator, is 40% more than that of the Sun.[4]
Planetary system
[edit]In 2019 Transiting Exoplanet Survey Satellite (TESS) discovered periodic dips on TOI-6894's brightness, which would be a signature of an exoplanet that periodically transits its host star as seen from Earth.[8] Confirmation was enabled by a team of scientists lead by Edward M. Bryant, which used photometry and Doppler spectroscopy to confidently confirm that the dips were caused by an exoplanet.[4] Named TOI-6894 b, where TOI is "TESS Object of Interest", this exoplanet has an orbital period of about 3.37 days and an average separation of 0.026 astronomical units (3,900,000 km). This somewhat close separation mean it is receiving 5.5 times the radiation Earth receives from the Sun. The equilibrium temperature is 418 K (145 °C; 293 °F), assuming an albedo of 0.1.[4]
The planet has a large radius of 9.6 Earth radii (R🜨), or about 0.855 RJ, contrasting with its small host star. This make planetary transits deep, with 17% of the stellar surface blocked at maximum. Its mass, measured from the gravitational pull it exerts on the star, is 53 times that of Earth mass (ME) (or 0.168 MJ), and given the relatively high metallicity of host star, it is estimated that elements heavier than hydrogen and helium, what astronomers term metals, make up 12±2 M🜨 (or 22% of the total).[4]
TOI-6894 b is unusual on that it has a relatively high mass while orbiting a low-mass star. Current knowledge predicts that smaller stars, such as TOI-6894, should also have a small amount of material in their protoplanetary disks. It is believed that stars with masses lower than 0.3 M☉ should not form gas giants, yet several examples of such planets, as LHS 3154 b, TZ Arietis b and GJ 3512 b have been found, posing challenges to planetary formation theories.[4]
The core accretion model suggest that gas giants form from the accretion of gas around a sufficiently massive core, which forms quickly enough to gain a large amount of gases. In this system, the relatively low amount of solid material in the primordial disk makes the formation of a sufficiently massive core difficult. Another plausible scenario is that TOI-6894 b's massive core accreted heavy elements before accreting gas. The predicted amount of solid material in disks around observed low-mass intermediate-age protostars is still lower than that the 12 ME in TOI-6894 b, but those values are potentially severly underestimated, and the properties of most observed protoplanetary disks are poorly constrained. Additionally, it has been theorized that such massive planets can form during the very early stages of star formation, where the dust amount is high enough, and combined with the rarity of planets like TOI-6894 b, it is still possible that it formed via the those pathways.[4]
Alternatively, the planet may have formed in a wider orbit around a disk that was gravitationally unstable and then condensed into a planet. At some point, it migrated to its current position.[4]
TOI-6894 b appears promising for characterization of its atmosphere, which can give further insights to its formation history. Based on its amount of radiation received by its host star, it is expected that the atmosphere is dominated by methane-based chemistry.[4]
| Companion (in order from star) |
Mass | Semimajor axis (AU) |
Orbital period (days) |
Eccentricity | Inclination | Radius |
|---|---|---|---|---|---|---|
| b | 0.168±0.022 MJ | 0.02604±0.00045 | 3.37077196(59) | 0.029±0.030 | 89.58+0.10 −0.07° |
0.855±0.022 RJ |
References
[edit]- ^ Roman, Nancy G. (1987). "Identification of a constellation from a position". Publications of the Astronomical Society of the Pacific. 99 (617): 695. Bibcode:1987PASP...99..695R. doi:10.1086/132034. Constellation record for this object at VizieR.
- ^ a b c d e 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 Lasker, Barry M.; Lattanzi, Mario G.; McLean, Brian J.; Bucciarelli, Beatrice; Drimmel, Ronald; Garcia, Jorge; Greene, Gretchen; Guglielmetti, Fabrizia; Hanley, Christopher; Hawkins, George; Laidler, Victoria G.; Loomis, Charles; Meakes, Michael; Mignani, Roberto; Morbidelli, Roberto; Morrison, Jane; Pannunzio, Renato; Rosenberg, Amy; Sarasso, Maria; Smart, Richard L.; Spagna, Alessandro; Sturch, Conrad R.; Volpicelli, Antonio; White, Richard L.; Wolfe, David; Zacchei, Andrea (2008). "The Second-Generation Guide Star Catalog: Description and Properties". The Astronomical Journal. 136 (2): 735. arXiv:0807.2522. Bibcode:2008AJ....136..735L. doi:10.1088/0004-6256/136/2/735.
- ^ a b c d e f g h i j k Bryant, Edward M.; Jordán, Andrés; Hartman, Joel D.; Bayliss, Daniel; Sedaghati, Elyar; Barkaoui, Khalid; Chouqar, Jamila; Pozuelos, Francisco J.; Thorngren, Daniel P.; Timmermans, Mathilde; Almenara, Jose Manuel; Chilingarian, Igor V.; Collins, Karen A.; Gan, Tianjun; Howell, Steve B. (June 2025). "A transiting giant planet in orbit around a 0.2-solar-mass host star". Nature Astronomy. arXiv:2506.07931. Bibcode:2025NatAs.tmp..129B. doi:10.1038/s41550-025-02552-4. ISSN 2397-3366.
{{cite journal}}: CS1 maint: bibcode (link) - ^ a b c d Cutri, R. M.; Skrutskie, M. F.; van Dyk, S.; Beichman, C. A.; Carpenter, J. M.; Chester, T.; Cambresy, L.; Evans, T.; Fowler, J.; Gizis, J.; Howard, E.; Huchra, J.; Jarrett, T.; Kopan, E. L.; Kirkpatrick, J. D. (2003). "2MASS All Sky Catalog of point sources". The IRSA 2MASS All-Sky Point Source Catalog. Bibcode:2003tmc..book.....C.
- ^ "TOI-6894 Overview". NASA Exoplanet Archive.
- ^ "TIC 67512645". SIMBAD. Centre de données astronomiques de Strasbourg.
- ^ a b "ExoFOP TIC 67512645". exofop.ipac.caltech.edu. Retrieved 2025-06-27.
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