| Observation data Epoch J2000.0 Equinox J2000.0 | |
|---|---|
| Constellation | Cetus |
| Right ascension | 02h 32m 09.42241s[1] |
| Declination | −01° 02′ 05.6166″[1] |
| Apparent magnitude (V) | +5.36[2] |
| Characteristics | |
| Evolutionary stage | red clump[3] |
| Spectral type | K1 III[4] or G3 III[5] |
| B−Vcolor index | +1.004±0.002[2] |
| Astrometry | |
| Radial velocity (Rv) | −6.34±0.13[1] km/s |
| Proper motion (μ) | RA: −23.268mas/yr[1] Dec.: −30.987mas/yr[1] |
| Parallax (π) | 12.1717±0.0962 mas[1] |
| Distance | 268 ± 2 ly (82.2 ± 0.6 pc) |
| Absolute magnitude (MV) | 0.808[6] |
| Details | |
| Mass | 1.92+0.07 −0.08[7] M☉ |
| Radius | 10.57+0.17 −0.16[3] R☉ |
| Luminosity | 51.8+1.5 −2.5[7] L☉ |
| Surface gravity (log g) | 2.67±0.04[3] cgs |
| Temperature | 4,830±20[3] K |
| Metallicity[Fe/H] | +0.10+0.08 −0.05[7] dex |
| Rotational velocity (v sin i) | 3.2±0.5[8] km/s |
| Age | 1.41±0.01[3] Gyr |
| Other designations | |
| 75 Cet,BD−01°353,GC 3043,HD 15779,HIP 11791,HR 739,SAO 129959[9] | |
| Database references | |
| SIMBAD | data |
| Exoplanet Archive | data |
75 Ceti is astar in theequatorialconstellation ofCetus with at least two planets.[7] It is visible to the naked eye as a dim, orange-hued star with anapparent visual magnitude of +5.36.[2] The star is located 268light-years (82parsecs) distant from the Sun, based onparallax, but is drifting closer with aradial velocity of −6 km/s.[1]
InChinese,天囷 (Tiān Qūn), meaningCircular Celestial Granary, refers to an asterism consisting ofα Ceti,κ1 Ceti,λ Ceti,μ Ceti,ξ1 Ceti,ξ2 Ceti,ν Ceti,γ Ceti,δ Ceti, 75 Ceti,70 Ceti,63 Ceti and66 Ceti. Consequently, 75 Ceti itself is known as the Tenth Star of Circular Celestial Granary.[10]
This is an aginggiant star with astellar classification of K1 III,[4] having exhausted the supply of hydrogen at itscore and expanded to 10.6[11] times theSun's radius, or 0.05 AU. It is ared clump giant,[3] which indicates it is on thehorizontal branch and is generating energy throughhelium fusion at the core. The star is 1.4[3] billion years old with 1.9[3] times theSun's mass. It is radiating 56[11] times theluminosity of the Sun from its swollenphotosphere at aneffective temperature of 4,846 K.[11] There is a companion star just over half the Sun's mass at a separation of 11.5arcseconds, corresponding to 958AU.[12]
A planetary companion was discovered byDoppler measurements at theOkayama Astrophysical Observatory, and announced in 2012. The planet's discoverers consider the planet, designated 75 Ceti b, to be "typical" ofgas giants.[5] Note that (like many recorded planets) b takes in much moreinsolation than does Jupiter and, indeed, Earth.[13]
There may be additional periodic factors in the data, corresponding tom sini of around0.4 MJ and1 MJ, at distances of ~0.9 AU and ~4 AU, wherei is theorbital inclination andm is the planet's actual mass.[5] In 2023, the presence of a second, Jupiter-mass planet orbiting at 4 AU (75 Ceti c) was confirmed, which is more irradiated than Earth as well. The shorter period signal corresponding to a possible planet at 0.9 AU was found to be an alias of the true period of planet c.[7]
| Companion (in order from star) | Mass | Semimajor axis (AU) | Orbital period (days) | Eccentricity | Inclination | Radius |
|---|---|---|---|---|---|---|
| b | ≥2.479+0.074 −0.090 MJ | 1.912+0.002 −0.003 | 696.62+1.33 −1.69 | 0.093+0.026 −0.042 | — | — |
| c | ≥0.912+0.088 −0.143 MJ | 3.929+0.058 −0.052 | 2051.62+45.98 −40.47 | 0.023+0.191 −0.003 | — | — |
