14 Herculis c

Discovery

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

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.

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

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, 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.

References

References

1. "Frigid Exoplanet in Strange Orbit Imaged by NASA's Webb".
2. Goździewski, K.. (2006). "Orbital Configurations and Dynamical Stability of Multiplanet Systems around Sun-like Stars HD 202206, 14 Herculis, HD 37124, and HD 108874". [[The Astrophysical Journal]].
3. Wittenmyer, R. A.. (2007). "Long-Period Objects in the Extrasolar Planetary Systems 47 Ursae Majoris and 14 Herculis". [[The Astrophysical Journal]].
4. (2021). "The California Legacy Survey. I. A Catalog of 178 Planets from Precision Radial Velocity Monitoring of 719 Nearby Stars over Three Decades". The Astrophysical Journal Supplement Series.
5. (1 December 2021). "14 Her: A Likely Case of Planet–Planet Scattering". The Astrophysical Journal Letters.
6. (August 2022). "3D Selection of 167 Substellar Companions to Nearby Stars". [[The Astrophysical Journal Supplement Series]].
7. (May 2023). "The 14 Her Planetary System: Companion Masses and Architecture from Radial Velocities and Astrometry". [[The Astronomical Journal]].
8. (June 2025). "JWST Coronagraphic Images of 14 Her c: a Cold Giant Planet in a Dynamically Hot, Multi-planet System". [[The Astrophysical Journal Letters]].
9. (2025). "Updated Mutual Inclination Measurement for 14 Her b and C". Research Notes of the AAS.
10. (January 2004). "The ELODIE survey for northern extra-solar planets. III. Three planetary candidates detected with ELODIE". Astronomy and Astrophysics.