109 Piscium b

109 Piscium b (aka HD 10697 b) is a long-period extrasolar planet discovered in orbit around 109 Piscium. It is about 5.74 times the mass of Jupiter and is likely to be a gas giant. As is common for long-period planets discovered around other stars, it has an orbital eccentricity greater than that of Jupiter.

109 Piscium b

Render of 109 Piscium b made with SpaceEngine
Discovery[1][2]
Discovered by	California and Carnegie Planet Search
Discovery site	W. M. Keck Observatory
Discovery date	November 1, 1999
Detection method	Doppler spectroscopy
Orbital characteristics[3]
Semi-major axis	2.051+0.079 −0.087 AU
Eccentricity	0.104+0.009 −0.008
Orbital period (sidereal)	2.944 ± 0.002 years (1,075.30 ± 0.73 d)
Inclination	86.116°+19.957° −20.530°
Longitude of ascending node	38.852°+15.084° −21.589°
Time of perihelion	2,449,333.898+14.739 −15.380
Argument of perihelion	112.816°+5.254° −5.448°
Semi-amplitude	114.583+1.067 −1.196 m/s
Star	109 Piscium
Physical characteristics[3]
Mean radius	1.152 RJ[4]
Mass	5.743+1.011 −0.289 MJ

The discoverers estimate its effective temperature as 264 K from solar heating, but it could be at least 10 to 20 K warmer because of internal heating.^[2] It orbits within the habitable zone.^[1]

Preliminary astrometric measurements suggested that the orbital inclination is 170.3°,^[5] yielding an object mass of 38 times that of Jupiter, which would make it a brown dwarf. However, subsequent analysis indicates that the precision of the measurements used to derive the astrometric orbit is insufficient to constrain the parameters.^[6] A more plausible suggestion is that this planet shares its star's inclination, of 69⁺²¹
₋₂₆°.^[7][8] In 2022, the inclination and true mass of 109 Piscium b were measured via astrometry. The inclination estimate is consistent with that of the stellar rotation.^[3]

See also

• 54 Piscium b – another nearby planet in the constellation of Pisces
• List of exoplanets discovered before 2000