HD 187123

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**HD 187123**
Observation data Equinox 2000
Constellation	Cygnus
Right ascension	19^h 46^m 58.11^s
Declination	+34° 25' 10.29"
Apparent magnitude (V)	7.89
Distance	156.28 ly (47.92 pc)
Spectral type	G5
Other designations
BD+34°3708, HIP 97336, SAO 68845

HD 187123 is an 8th magnitude star in the constellation of Cygnus. Like our Sun, it a yellow dwarf (spectral type G5 V). Being at a distance of about 160 light years it is not visible to the unaided eye. However, it should be easy target with binoculars or small telescope.

In 1998 the California and Carnegie Planet Search team, after following a suggestion by Kevin Apps, a Briton who at the time was an undergraduate student ^[1] found a possible planet orbiting the star. There are also indications of another, more distant body orbiting the star.

1 HD 187123 b
2 HD 187123 c
3 References
4 External links

[edit] HD 187123 b

**HD 187123 b**
Orbital elements

Semi-major axis a:	0.042 AU
Eccentricity e:	0.03 ± 0.003
Orbital period P:	3.097 d
Inclination i:	?°
Longitude of periastron ω:	20°
Time of periastron τ:	2,451,029.73 JD
Physical characteristics
Mass:	>0.52 M_J
Radius:	? R_J
Density:	? kg/m³
Temperature:	? K
Discovery
Discovery date:	1998
Detection method(s):
Discoverer(s):	Butler, Marcy, Vogt, Apps

HD 187123 b is a typical "hot Jupiter". It has a mass about half that of Jupiter and it orbits in a very tight, round orbit around the star every three days. However, there is a very slight possibility that the signal, thought to be caused by the planet, may be from starspots and stellar pulsations instead.

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

[edit] HD 187123 c

HD 187123 may have another planet further out, with an orbital period over three years. The data does not yet allow a precise estimation for its orbit and minimum mass, but further observations will either prove or disprove this planet candidate.