24 Sextantis
| Observation data Epoch 2000 Equinox 2000 | |
|---|---|
| Constellation | Lyra |
| Right ascension | 10h 23m 28.37066s[1] |
| Declination | –00° 54′ 08.0888″[1] |
| Apparent magnitude (V) | 6.61 ± 0.04[2] |
| Characteristics | |
| Spectral type | G5 IV |
| B−V color index | 0.92 ± 0.01[2] |
| Astrometry | |
| Radial velocity (Rv) | 7.08 ± 0.16[3] km/s |
| Proper motion (μ) | RA: +66.21[1] mas/yr Dec.: –34.92[1] mas/yr |
| Parallax (π) | 12.91 ± 0.38[1] mas |
| Distance | 253 ± 7 ly (77 ± 2 pc) |
| Absolute magnitude (MV) | 2.17 ± 0.06[2] |
| Details | |
| Mass | 1.54 ± 0.08[2] M☉ |
| Radius | 4.9 ± 0.08[2] R☉ |
| Luminosity | 14.6 ± 0.1[2] L☉ |
| Surface gravity (log g) | 3.5 ± 0.1[2] cgs |
| Temperature | 5,098 ± 44[2] K |
| Metallicity [Fe/H] | −0.03 ± 0.04[2] dex |
| Rotational velocity (v sin i) | 2.77 ± 0.5[2] km/s |
| Age | 2.7 ± 0.4[2] Gyr |
| Other designations | |
24 Sextantis (often shortened to 24 Sex and known within the amateur stargazing community as RTG) is the Flamsteed designation of a 7th-magnitude star located approximately 253 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 G5 IV. 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
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.[4] 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. These two jovian planets are dancing around each other gravitationally.[4]
| 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
References
- 1 2 3 4 5 van Leeuwen, F. (November 2007), "Validation of the new Hipparcos reduction", Astronomy and Astrophysics 474 (2): 653–664, arXiv:0708.1752, Bibcode:2007A&A...474..653V, doi:10.1051/0004-6361:20078357
- 1 2 3 4 5 6 7 8 9 10 11 12 Johnson, John Asher; et al. (January 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
- ↑ 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
- 1 2 "Astronomers find planets in unusually intimate dance around dying star". Astronomy Magazine. July 29, 2010. Retrieved 2011-01-13.
- ↑ Jean Schneider (2011). "Notes for star 24 Sex". Extrasolar Planets Encyclopaedia. Retrieved 30 September 2011.
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Coordinates: 
10h 23m 28s, −00° 54′ 08″