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HD 28185

2007 Schools Wikipedia Selection. Related subjects: Space (Astronomy)

   CAPTION: HD 28185

                     Observation data
   Epoch J2000.0
   Constellation             Eridanus
   Right ascension           04^h 26^m 26.3205^s
   Declination               -10° 33' 02.955"
   Apparent magnitude (V)    +7.81
                     Characteristics
   Spectral type             G5V
   B-V colour index          0.750
   U-B colour index           ?
   Variable type             none
                        Astrometry
   Radial velocity (R[v])    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 (M[V]) +4.81
                         Details
   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 × 10^9 years
                    Other designations
   BD −10°919, SAO 149631, HIP 20723, GSC 05317-00733
                   Database references
   SIMBAD                    data

   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.

        Companion
   (In order from star)     Mass
                          ( M[J])    Orbital period
                                         (days)    Semimajor axis
                                                       ( AU)     Eccentricity
            b           >5.72 ± 0.93  383.0 ± 2.0  1.031 ± 0.060 0.070 ± 0.040

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