HD 240210

HD 240210

Observation data Epoch J2000.0      Equinox J2000.0
Constellation	Cassiopeia
Right ascension	23^h 10^m 29.22633^s[1]
Declination	+57° 01′ 46.0277″[1]
Apparent magnitude (V)	8.33[2]
Characteristics
Evolutionary stage	giant[2]
Spectral type	K3III
B−V color index	1.63
Astrometry
Radial velocity (Rv)	+8.57±0.05[1] km/s
Proper motion (μ)	RA: 18.492[1] mas/yr Dec.: 6.883[1] mas/yr
Parallax (π)	2.6570 ± 0.0349 mas[1]
Distance	1,230 ± 20 ly (376 ± 5 pc)
Absolute bolometric magnitude (Mbol)	+0.38[2]
Details
Mass	1.25±0.25[2] M☉
Radius	25.46+1.16 −0.75[1] R☉
Luminosity	152±3[1] L☉
Surface gravity (log g)	2.31±0.11[2] cgs
Temperature	4,019+60 −90[1] K
Metallicity [Fe/H]	−0.18±0.12[2] dex
Rotation	> 654 days[2]
Rotational velocity (v sin i)	< 1.0[2] km/s
Age	3.0+2.9 −1.5[3] Gyr
Other designations
BD+56°2959, HD 240210, SAO 35195, PPM 41549[4]
Database references
SIMBAD	data
Exoplanet Archive	data

HD 240210 is a star in the northern constellation of Cassiopeia. It has an orange hue but is too faint to be viewed with the naked eye, having an apparent visual magnitude of 8.33.^[2] Parallax measurements provide an estimate of its distance from the Sun as approximately 1,230 light years. It is drifting further away with a radial velocity of +8.6 km/s.^[1]

This is an aging giant star with a class of K3,^[2] which has exhausted the supply of hydrogen at its core and expanded to 25^[1] times the radius of the Sun. It is around three^[3] billion years old with 1.3^[2] times the Sun's mass. The star is radiating 152 times the luminosity of the Sun from its enlarged photosphere at an effective temperature of 4,019 K.^[1] It is spinning slowly, with each rotation taking at least 1.8 years.^[2]

On June 10, 2009 a planet orbiting the star was discovered by Niedzielski et al. This exoplanet is a 6.9 or greater Jupiter mass planet. Evidence for additional planetary companions has been found.^[5]

The HD 240210 planetary system^[2]

Companion (in order from star)	Mass	Semimajor axis (AU)	Orbital period (days)	Eccentricity	Inclination	Radius
b	≥ 6.90 MJ	1.33	501.75±2.33	0.15±0.02	—	—

See also

• BD+14°4559
• BD+20°2457
• List of extrasolar planets
• John Flamsteed

References

1. 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.
2. Niedzielski, A.; et al. (2009). "Substellar-mass Companions to the K-dwarf BD+14 4559 and the K-giants HD 240210 and BD+20 2457". The Astrophysical Journal. 707 (1): 768–777. arXiv:0906.1804. Bibcode:2009ApJ...707..768N. doi:10.1088/0004-637X/707/1/768. S2CID 16877069.
3. Adamczyk, M.; et al. (2016). "Masses and luminosities for 342 stars from the PennState-Toruń Centre for Astronomy Planet Search". Astronomy and Astrophysics. 587: A119. arXiv:1510.07495. Bibcode:2016A&A...587A.119A. doi:10.1051/0004-6361/201526628. S2CID 119299522.
4. "HD 240210". SIMBAD. Centre de données astronomiques de Strasbourg. Retrieved 2019-11-17.
5. Adamów, M.; et al. (July 2011). Martin, E.L.; Ge, J.; Lin, W. (eds.). A search for planets around intermediate Mass Stars with the Hobby-Eberly Telescope. Research, Science and Technology of Brown Dwarfs and Exoplanets: Proceedings of an International Conference held in Shangai on Occasion of a Total Eclipse of the Sun, Shangai, China. EPJ Web of Conferences. Vol. 16. Bibcode:2011EPJWC..1602005A. doi:10.1051/epjconf/20111602005. 02005.