| Observation data Epoch J2000 Equinox J2000 | |
|---|---|
| Constellation | Cassiopeia |
| Right ascension | 23 15 42.22441 |
| Declination | +58° 02′ 35.6705″ |
| Apparent magnitude (V) | 8.19 |
| Characteristics | |
| Spectral type | K2III |
| B−V color index | 1.682±0.029 |
| Astrometry | |
| Radial velocity (Rv) | −24.82±0.04 km/s |
| Proper motion (μ) | RA: −0.203 mas/yr Dec.: −4.290 mas/yr |
| Parallax (π) | 1.0437 ± 0.0364 mas |
| Distance | 3,100 ± 100 ly (960 ± 30 pc) |
| Details | |
| Mass | 1.69±0.42 or 0.61 M☉ |
| Radius | 78.13+7.31 −5.66 R☉ |
| Luminosity | 1,244±65 L☉ |
| Temperature | 3,878+148 −170 K |
| Metallicity | −0.26±0.07 dex |
| Rotation | ≥ 1010 d |
| Age | 270 Myr |
| Other designations | |
| BD+57°2714, Gaia DR2 2010336687886382592, HD 240237, HIP 114840, SAO 35269, 2MASS J23154222+5802358 | |
| Database references | |
| SIMBAD | data |
HD 240237 is a star in the northern constellation of Cassiopeia. It is an orange star that can be viewed with binoculars or a small telescope, but is too faint to be seen with the naked eye at an apparent visual magnitude of 8.19. This object is located at a distance of approximately 3,100 light years away from the Sun based on parallax, but is drifting closer with a radial velocity of −25 km/s.
This is an aging giant star with a stellar classification of K2III; a star that has exhausted the supply of hydrogen at its core and expanded to 78 times the radius of the Sun. S. Gettel and associates (2011) estimate the star is around 270 million years old with 1.7 times the mass of the Sun. However, S. G. Sousa and associates found a much lower mass of 0.61 times the mass of the Sun. It is radiating 1,244 times the Sun's luminosity from its enlarged photosphere at an effective temperature of 3,878 K.
Planetary system
In 2011, Gettel et al. announced the discovery of a planet orbiting this star. They estimated a mass around 5 times that of Jupiter, with an orbital period of 2.042 years and a moderate eccentricity. Sousa et al. (2015) gave a much lower estimate of 1.53 MJ. The designation b for this object, derives from the order of discovery. The designation of b is given to the first planet orbiting a given star, followed by the other lowercase letters of the alphabet. In the case of HD 240237, there was only one planet, so only the letter b is used.
| Companion (in order from star) |
Mass | Semimajor axis (AU) |
Orbital period (days) |
Eccentricity | Inclination | Radius |
|---|---|---|---|---|---|---|
| b | 5.3 MJ | 1.9 | 745.7±13.8 | 0.4±0.1 | — | — |
References
- ^ 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.
- ^ Anderson, E.; Francis, Ch. (2012). "XHIP: An extended hipparcos compilation". Astronomy Letters. 38 (5): 331. arXiv:1108.4971. Bibcode:2012AstL...38..331A. doi:10.1134/S1063773712050015. S2CID 119257644.
- ^ Gettel, S.; et al. (2011). "Substellar-Mass Companions to the K-Giants HD 240237, BD +48 738 and HD 96127". The Astrophysical Journal. 745 (1): 28. arXiv:1110.1641. Bibcode:2012ApJ...745...28G. doi:10.1088/0004-637X/745/1/28. S2CID 119116402.
- ^ Sousa, S. G.; et al. (April 2015). "Homogeneous spectroscopic parameters for bright planet host stars from the northern hemisphere . The impact on stellar and planetary mass". Astronomy & Astrophysics. 576: 8. arXiv:1503.02443. Bibcode:2015A&A...576A..94S. doi:10.1051/0004-6361/201425227. S2CID 73575554. A94.
- ^ "HD 240237". SIMBAD. Centre de données astronomiques de Strasbourg. Retrieved 7 June 2014.
- Hessman, F. V.; et al. (2010). "On the naming convention used for multiple star systems and extrasolar planets". arXiv:1012.0707 .
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