HD 28185

HD 28185 is a yellow dwarf star similar to our Sun located about 128.6 light-years away from Earth in the constellation Eridanus. The designation HD 28185 refers to its entry in the Henry Draper catalogue. The star is known to possess one long-period extrasolar planet.

HD 28185

Observation data Epoch J2000.0      Equinox J2000.0
Constellation	Eridanus
Right ascension	04^h 26^m 26.3227^s[1]
Declination	−10° 33′ 02.9455″[1]
Apparent magnitude (V)	+7.81
Characteristics
Spectral type	G5V
U−B color index	?
B−V color index	0.750
Variable type	none
Astrometry
Radial velocity (Rv)	49.6 km/s
Proper motion (μ)	RA: 84.071±0.045[1] mas/yr Dec.: −59.750±0.039[1] mas/yr
Parallax (π)	25.3642 ± 0.0407[1] mas
Distance	128.6 ± 0.2 ly (39.43 ± 0.06 pc)
Absolute magnitude (MV)	+4.68[note 1]
Details
Mass	1.0 ± 0.1[2] M☉
Radius	1.15 ± 0.03[2] R☉
Luminosity	1.18 ± 0.01[2] L☉
Surface gravity (log g)	4.33 ± 0.03[2] cgs
Temperature	5609 ± 41[2] K
Metallicity	0.24 (173%)
Rotation	30 days
Age	4.8 ± 4.4[2] Gyr
Other designations
BD–10°919, SAO 149631, HIP 20723, GSC 05317-00733
Database references
SIMBAD	data
Extrasolar Planets Encyclopaedia	data

Distance and visibility

According to measurements from the Gaia spacecraft, HD 28185 has a parallax of 25.3642 milliarcseconds,[1] which corresponds to a distance of 39.43 parsecs (128.6 light-years). Since the star is located further than 25 parsecs from Earth, it is not listed in the Gliese Catalogue of Nearby Stars. With an apparent magnitude of 7.81, the star is not visible with the naked eye, though it can be seen using binoculars.

Stellar characteristics

HD 28185 is similar to our Sun in terms of mass, radius, and luminosity. The star is on the main sequence and is generating energy by fusing hydrogen in its core. The spectral type of G5V implies HD 28185 is cooler than the Sun. Like the majority of extrasolar planet host stars, HD 28185 is metal-rich relative to the Sun, containing around 173% of the solar abundance of iron. The star rotates slower than the Sun, with a period of around 30 days, compared to 25.4 days for the Sun.

Based on the star's chromospheric activity, HD 28185 is estimated to have an age of around 2,900 million years. On the other hand, evolutionary models give an age of around 7,500 million years and a mass 0.99 times that of our Sun.[3] The higher luminosity and longer rotation period favour an older age for the star.

Planetary system

In 2001 an extrasolar planet similar in size to Jupiter designated HD 28185 b was discovered in orbit around the star with a period of 1.04 years.[3][4] Unlike many long-period extrasolar planets, it has a low orbital eccentricity.[5] The planet experiences similar insolation to Earth, which has led to speculations about the possibilities for habitable moons.[6][7] In addition, numerical simulations suggest that low-mass planets located in the gas giant's Trojan points would be stable for long periods.[8] The planet's existence was independently confirmed by the Magellan Planet Search Program in 2008.[9]

The star also shows evidence of a long-term radial velocity trend, which may indicate the presence of an additional outer companion.[10]

The HD 28185 planetary system[3]

Companion (in order from star)	Mass	Semimajor axis (AU)	Orbital period (days)	Eccentricity	Inclination	Radius
b	≥5.7 MJ	1.031 ± 0.060	383 ± 2	0.07 ± 0.04	—	—

See also

• 51 Pegasi
• Iota Horologii

Notes

1. Derived from apparent magnitude and parallax: ${\displaystyle \scriptstyle M_{V}=m_{V}-5\log _{10}\left({\frac {100}{\pi }}\right)}$

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. Bonfanti, A.; et al. (2015). "Revising the ages of planet-hosting stars". Astronomy and Astrophysics. 575. A18. arXiv:1411.4302. Bibcode:2015A&A...575A..18B. doi:10.1051/0004-6361/201424951.
3. Santos, N.; et al. (2001). "The CORALIE survey for southern extra-solar planets VI. New long-period giant planets around HD 28185 and HD 213240". Astronomy and Astrophysics. 379 (3): 999–1004. arXiv:astro-ph/0106255. Bibcode:2001A&A...379..999S. doi:10.1051/0004-6361:20011366.
4. "Exoplanets: The Hunt Continues!" (Press release). Garching, Germany: European Southern Observatory. April 4, 2001. Retrieved December 27, 2012.
5. Butler, R. P.; et al. (2006). "Catalog of Nearby Exoplanets". The Astrophysical Journal. 646 (1): 505–522. arXiv:astro-ph/0607493. Bibcode:2006ApJ...646..505B. doi:10.1086/504701.
6. Mullen, L. (2001). "Extrasolar Planets with Earth-like Orbits". Archived from the original on 29 September 2006. Retrieved 22 July 2006.
7. Jones, Barrie W.; Sleep, P. Nick; Underwood, David R. (2006). "Habitability of Known Exoplanetary Systems Based on Measured Stellar Properties". The Astrophysical Journal. 649 (2): 1010–1019. arXiv:astro-ph/0603200. Bibcode:2006ApJ...649.1010J. doi:10.1086/506557.
8. Schwarz, R.; Dvorak, R.; Süli, Á.; Érdi, B. (2007). "Survey of the stability region of hypothetical habitable Trojan planets". Astronomy and Astrophysics. 474 (3): 1023–1029. Bibcode:2007A&A...474.1023S. doi:10.1051/0004-6361:20077994.
9. Minniti, Dante; et al. (2009). "Low-Mass Companions for Five Solar-Type Stars From the Magellan Planet Search Program". The Astrophysical Journal. 693 (2): 1424–1430. arXiv:0810.5348. Bibcode:2009ApJ...693.1424M. doi:10.1088/0004-637X/693/2/1424.
10. Chauvin, G.; Lagrange, A.-M.; Udry, S.; Fusco, T.; Galland, F.; Naef, D.; Beuzit, J.-L.; Mayor, M. (2006). "Probing long-period companions to planetary hosts. VLT and CFHT near infrared coronographic imaging surveys". Astronomy and Astrophysics. 456 (3): 1165–1172. arXiv:astro-ph/0606166. Bibcode:2006A&A...456.1165C. doi:10.1051/0004-6361:20054709.

External links