14 Herculis c

14 Herculis c or 14 Her c is the outermost of two known exoplanets orbiting the star 14 Herculis, approximately 58.4 light-years away in the constellation of Hercules. The planet has a mass that would make it a gas giant roughly the same size as Jupiter but much more massive.

14 Herculis c

Direct image of 14 Herculis c taken with the James Webb Space Telescope. Its host star is blocked by a coronagraph.
Discovery[1][2]
Discovered by	Goździewski et al.; Rosenthal et al.
Discovery site	Observatoire de Haute-Provence,[3] Keck & AFP[2]
Discovery date	17 November 2005 (candidate) 2 July 2021 (confirmed)
Detection method	Doppler spectroscopy
Designations
Alternative names	HD 145675 c
Orbital characteristics
Semi-major axis	20.0+12.0 −4.9 AU[4] 28.1+6.4 −6.8 AU[5]
Eccentricity	0.64+0.06 −0.10[5]
Orbital period (sidereal)	52,160±1,030 days (142.8±2.8 years)[4]
Inclination	111.9°+5.4° −5.5°[5]
Longitude of ascending node	205.1°+7.448° −10.31°[4]
Time of periastron	2,451,779±33 JD[6]
Argument of periastron	172.5°+4.011° −4.584°[4]
Semi-amplitude	50.8±0.4 m/s[6]
Star	14 Herculis
Physical characteristics[4]
Mean radius	1.03±0.01 RJ
Mass	7.9+1.6 −1.2 MJ
Surface gravity	4.25±0.15 cgs
Temperature	275 K (2 °C; 35 °F)

Discovery

14 Herculis c was discovered by the radial velocity method. Its discovery was first reported in 2005 (published in 2006),^[1] using data from the ELODIE Planet Search survey.^[3] It remained a planet candidate until its existence was securely confirmed in 2021.^[2]

According to a 2007 analysis, the existence of a second planet in the 14 Herculis system was "clearly" supported by the evidence, but the planet's parameters were not precisely known. It may be in a 4:1 resonance with the inner planet 14 Herculis b.^[7]

The inclination and true mass of 14 Herculis c were measured in 2021, using data from Gaia,^[8] and refined by further astrometric studies in 2022 and 2023,^[9][6] as well by a 2025 study using James Webb Space Telescope astrometry. The inclination is 116°, corresponding to a true mass of 7.1 M_J.^[6]

Direct imaging

The planet was directly imaged with the James Webb Space Telescope's NIRCam instrument in 2025. The observations determined a temperature of 275 K (2 °C), making it one of the coldest exoplanets directly imaged. They also re-measured its orbital elements, finding it to be closer to the star, at around 15 AU, on a highly eccentric orbit, as well as measuring its orbital inclination, finding it to be misaligned with 14 Herculis b by 40°. At wavelengths of 4.4 μm, its apparent magnitude is fainter than expected, hinting at disequilibrium chemistry and/or water ice clouds.^[10][4]

See also

• Epsilon Eridani b
• Epsilon Indi Ab
• HD 222237