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HD 28185

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HD 28185
Observation data
Epoch J2000.0       Equinox J2000.0
Constellation Eridanus
Right ascension 04h 26m 26.3205s
Declination -10° 33′ 02.955″
Apparent magnitude (V) +7.81
Spectral type G5V
U−B colour index ?
B−V colour index 0.750
Variable type none
Radial velocity (Rv) 49.6 km/s
Proper motion (μ) RA: 80.85  mas/ yr
Dec.: -60.29  mas/ yr
Parallax (π) 25.28 ± 1.08 mas
Distance 129 ly
(39.6 pc)
Absolute magnitude (MV) +4.81
Mass 0.99 ± 0.07 M
Radius 1.04 R
Luminosity 1.02 L
Temperature 5705 K
Metallicity 173%
Rotation 30 days
Age 7.5 × 109 years
Other designations
BD −10°919, SAO 149631, HIP 20723, GSC 05317-00733
Database references

HD 28185 is a yellow dwarf star similar to our Sun located about 129 light-years away in the constellation Eridanus. The designation HD 28185 refers to its entry in the Henry Draper catalogue. As of 2006 the star is known to possess one long- period extrasolar planet.

Distance and visibility

According to measurements from the Hipparcos astrometric satellite, HD 28185 has a parallax of 25.28 milliarcseconds, which corresponds to a distance of 39.6 parsecs (129 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.

Planetary system

In 2001 an extrasolar planet designated HD 28185 b was discovered in orbit around the star with a period of 1.04 years. Unlike many long-period extrasolar planets, it has a low orbital eccentricity. The planet experiences similar insolation to Earth, which has led to speculations about the possibilities for habitable moons. In addition, numerical simulations suggest that low-mass planets located in the gas giant's Trojan points would be stable for long periods.

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

The HD 28185 system
(in order from star)
Mass Semimajor axis
( AU)
Orbital period
Eccentricity Radius
b >5.72 ± 0.93  MJ 1.031 ± 0.060 383.0 ± 2.0 0.070 ± 0.040
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