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] |
| 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) is 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 [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.[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 [edit]
References [edit]
- ^ a b c d e 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
- ^ a b c d e f g h i j k l Lowe, Thomas B. (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
- ^ a b "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.
