24 Sextantis
| Observation data Epoch J2000 Equinox J2000 | |
|---|---|
| Constellation | Sextans |
| Right ascension | 10h 23m 28.3694s[1] |
| Declination | –00° 54′ 08.0772″[1] |
| Apparent magnitude (V) | 6.61 ± 0.04[2] |
| Characteristics | |
| Spectral type | K0 IV[3] |
| B−V color index | 0.92 ± 0.01[2] |
| Astrometry | |
| Radial velocity (Rv) | 7.08 ± 0.16[4] km/s |
| Proper motion (μ) | RA: 65.220±0.167[1] mas/yr Dec.: −36.272±0.244[1] mas/yr |
| Parallax (π) | 13.8488 ± 0.1298 mas[1] |
| Distance | 236 ± 2 ly (72.2 ± 0.7 pc) |
| Absolute magnitude (MV) | 2.17 ± 0.06[2] |
| Details[2] | |
| Mass | 1.54 ± 0.08 M☉ |
| Radius | 4.9 ± 0.08 R☉ |
| Luminosity | 14.6 ± 0.1 L☉ |
| Surface gravity (log g) | 3.5 ± 0.1 cgs |
| Temperature | 5,098 ± 44 K |
| Metallicity [Fe/H] | −0.03 ± 0.04 dex |
| Rotational velocity (v sin i) | 2.77 ± 0.5 km/s |
| Age | 2.7 ± 0.4 Gyr |
| Other designations | |
| Database references | |
| SIMBAD | data |
24 Sextantis, often abbreviated as 24 Sex, is the Flamsteed designation of a 7th-magnitude star located approximately 236 light years away in the constellation of Sextans. At an apparent visual magnitude of 6.61,[2] this star can only be viewed from rural skies under good seeing conditions.
At the age of 2.8 billion years, it has reached an evolutionary stage called a subgiant star, having a stellar classification of K0 IV.[3] Previously it was an A-type main sequence star before using up the hydrogen at its core. It has 54% more mass than the Sun, but the outer envelope has become cooler than the Sun's as it slowly expands into a giant star.
The star is known to have two giant extrasolar planets.
Planetary system
[edit]On July 26, 2010 the California and Carnegie Planet Search team announced the discovery of two planets around 24 Sextantis along with two planets around HD 200964.[6] The inner planet is twice as massive as Jupiter and takes 453 days to orbit the star in a circular orbit at the average distance of 1.33 AU (199 Gm). The outer planet is 5/6 the mass of Jupiter and takes 883 days to orbit eccentrically around the star at the average distance of 2.08 AU (312 Gm).
The two planets are in a 2:1 resonance, meaning that the outer planet orbits the star once every time when the inner planet orbits the star twice.[6] The planetary system was found to be unstable in 2019.[7]
| Companion (in order from star) |
Mass | Semimajor axis (AU) |
Orbital period (days) |
Eccentricity | Inclination | Radius |
|---|---|---|---|---|---|---|
| b | ≥1.99+0.26 −0.38 MJ |
1.333+0.004 −0.009 |
452.8+2.1 −4.5 |
0.09+0.14 −0.06 |
— | — |
| c | ≥0.86+0.35 −0.26 MJ |
2.08+0.05 −0.02 |
883+32 −14 |
0.29+0.16 −0.09 |
— | — |
See also
[edit]References
[edit]- ^ a b c d e Brown, A. G. A.; et al. (Gaia collaboration) (August 2018). "Gaia Data Release 2: Summary of the contents and survey properties". Astronomy & Astrophysics. 616. A1. arXiv:1804.09365. Bibcode:2018A&A...616A...1G. doi:10.1051/0004-6361/201833051. Gaia DR2 record for this source at VizieR.
- ^ a b c d e Johnson, John Asher; et al. (2011). "Retired A Stars and Their Companions. VI. A Pair of Interacting Exoplanet Pairs Around the Subgiants 24 Sextanis and HD 200964". The Astronomical Journal. 141 (1). 16. arXiv:1007.4552. Bibcode:2011AJ....141...16J. doi:10.1088/0004-6256/141/1/16.
- ^ a b Houk, N.; Swift, C. (1999), "Michigan catalogue of two-dimensional spectral types for the HD Stars", Michigan Spectral Survey, 5, Bibcode:1999MSS...C05....0H.
- ^ Massarotti, Alessandro; et al. (January 2008), "Rotational and Radial Velocities for a Sample of 761 HIPPARCOS Giants and the Role of Binarity", The Astronomical Journal, 135 (1): 209–231, Bibcode:2008AJ....135..209M, doi:10.1088/0004-6256/135/1/209, S2CID 121883397
- ^ "24 Sextantis". SIMBAD. Centre de données astronomiques de Strasbourg. Retrieved 2019-09-17.
- ^ a b "Astronomers find planets in unusually intimate dance around dying star". Astronomy Magazine. July 29, 2010. Retrieved 2011-01-13.
- ^ Agnew, Matthew T; Maddison, Sarah T; Horner, Jonathan; Kane, Stephen R (June 2019). "Predicting multiple planet stability and habitable zone companions in the TESS era". Monthly Notices of the Royal Astronomical Society. 485 (4): 4703–4725. arXiv:1901.11297. doi:10.1093/mnras/stz345. Retrieved 28 April 2020.
- ^ Jean Schneider (2011). "Notes for star 24 Sex". Extrasolar Planets Encyclopaedia. Archived from the original on August 4, 2010. Retrieved 30 September 2011.
