HD 187123 b
Extrasolar planet List of extrasolar planets
Parent star

<tr> <td colspan="2">Star</td> <td>HD 187123</td></tr><tr> <td colspan="2">Constellation</td> <td>Cygnus</td></tr><tr> <td>Right ascension</td> <td style="text-align: center">(α)</td> <td>19h 46m 58.1130s</td></tr><tr> <td>Declination</td> <td style="text-align: center">(δ)</td> <td>+34° 25′ 10.288″</td></tr><tr><td colspan="2">Distance</td><td>156.28 ly
(47.92 pc)</td></tr><tr><td colspan="2">Spectral type</td> <td>G5V</td></tr>

Orbital elements

<tr><td>Semimajor axis</td><td style="text-align: center">(a)</td> <td>0.0426 AU</td></tr><tr> <td>Periastron</td> <td style="text-align: center">(q)</td> <td>0.0411 AU</td></tr><tr> <td>Apastron</td> <td style="text-align: center">(Q)</td> <td>0.0441 AU</td></tr><tr> <td>Eccentricity</td> <td style="text-align: center">(e)</td> <td>0.035 ± 0.015</td></tr><tr><td>Orbital period</td><td style="text-align: center">(P)</td> <td>3.097 d
(0.008479 y)</td></tr><tr> <td>Orbital speed</td> <td style="text-align: center">(υ)</td> <td>150 km/s</td></tr><tr> <td>Argument of
</td> <td style="text-align: center">(ω)</td> <td>20°</td></tr><tr> <td>Time of periastron</td> <td style="text-align: center">(T0)</td> <td>2,451,029.73 JD</td></tr><tr> <td>Semi-amplitude</td> <td style="text-align: center">(K)</td> <td>70.6 m/s</td></tr>

Physical characteristics

<tr><td>Mass</td><td style="text-align: center">(m)</td><td>>0.52 MJ</td></tr>

Discovery information

<tr> <td colspan="2">Discovery date</td> <td>9 September 1998</td></tr><tr> <td colspan="2">Discoverer(s)</td> <td>Butler, Marcy,
Vogt, Apps et al.</td></tr><tr> <td colspan="2">Discovery method</td> <td>radial velocity</td></tr><tr> <td colspan="2">Discovery site</td> <td>California, USA</td></tr><tr> <td colspan="2">Discovery status</td> <td>Published</td></tr>

HD 187123 b is a typical "hot Jupiter" located approximately 156 light-years away in the constellation of Cygnus, orbiting the star HD 187123. It has a mass about half that of Jupiter and it orbits in a very tight, round orbit around the star every three days.[1][2]

The star has also been monitored for possible transits by the planet, but none was found.

See alsoEdit


  1. (1998). A Planet with a 3.1 Day Period around a Solar Twin. Publications of the Astronomical Society of the Pacific 110 (754): 1389–1393.
  2. (2009). Ten New and Updated Multi-planet Systems, and a Survey of Exoplanetary Systems. The Astrophysical Journal 693 (2): 1084–1099.

External linksEdit

Coordinates: Sky map 19h 46m 58.1130s, +34° 25′ 10.288″

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