84 Ceti

84 Ceti is the Flamsteed designation for a binary star system^[4] in the equatorial constellation of Cetus. It has an apparent visual magnitude of 5.7,^[2] making it faintly visible to the naked eye from dark suburban skies. Parallax measurements with the Hipparcos spacecraft put this system at a distance of around 74 light years.^[1]

84 Ceti

Observation data Epoch J2000      Equinox J2000
Constellation	Cetus
Right ascension	02h 41m 13.99720s[1]
Declination	–00° 41′ 44.3845″[1]
Apparent magnitude (V)	5.709[2]
Characteristics
Spectral type	F7V[3] + K2V[4]
U−B color index	–0.047[2]
B−V color index	+0.522[2]
Astrometry
Radial velocity (Rv)	+3.90[5] km/s
Proper motion (μ)	RA: 216.51[1] mas/yr Dec.: –129.33[1] mas/yr
Parallax (π)	44.27 ± 0.84 mas[1]
Distance	74 ± 1 ly (22.6 ± 0.4 pc)
Details
84 Cet A
Mass	1.168[3] M☉
Radius	1.208 ± 0.029[3] R☉
Luminosity	2.133 ± 0.083[3] L☉
Temperature	6356 ± 46[3] K
Metallicity [Fe/H]	−0.15[3] dex
Rotational velocity (v sin i)	32.0[6] km/s
Age	2.1[3] Gyr
Other designations
84 Cet, BD–01 377, HD 16765, HIP 12530, HR 790, SAO 130055.[7]
Database references
SIMBAD	data

The primary, 84 Ceti A, is an F-type main sequence star with a stellar classification of F7V. It is slightly larger than the Sun, with 117% of the Sun's mass, 121% of the radius, and 213% of the luminosity.^[3] The abundance of elements more massive than helium is 71% of the Sun's and it has a relatively high projected rotational velocity of 32 km/s.^[6] This star is estimated to be less than half the age of the Sun, at 2.1 billion years.^[3]

The secondary component, 84 Ceti B, has a classification of K2V,^[4] making it a K-type main sequence star. It lies at an angular separation of 3.3″ from the primary, which is equivalent to a physical separation of at least 74.5 AU.^[4]

The space velocity components of this system are: –13(U), –25(V), –2(W) km/s.^[8] Based upon the position and motion, it is a candidate member of the Tucana-Horologium Association; this is a group of stars that share a similar motion through space and hence may have originated in the same molecular cloud.^[9] 84 Ceti is following an orbit through the Milky Way galaxy that has an eccentricity of 0.03, taking it as close as 22.3 kly (6.83 kpc) and as far as 26.2 kly (8.02 kpc) from the Galactic Center. The inclination of the orbital plane carries it as far as 260 ly (80 pc) away from the galactic plane.^[8]

References

1. van Leeuwen, F. (November 2007), "Validation of the new Hipparcos reduction", Astronomy and Astrophysics, 474 (2): 653–664, arXiv:0708.1752, Bibcode:2007A&A...474..653V, doi:10.1051/0004-6361:20078357, S2CID 18759600.
2. Rakos, K. D.; et al. (February 1982), "Photometric and astrometric observations of close visual binaries", Astronomy and Astrophysics Supplement Series, 47: 221–235, Bibcode:1982A&AS...47..221R.
3. Boyajian, Tabetha S.; et al. (July 2013), "Stellar Diameters and Temperatures. III. Main-sequence A, F, G, and K Stars: Additional High-precision Measurements and Empirical Relations", The Astrophysical Journal, 771 (1): 40, arXiv:1306.2974, Bibcode:2013ApJ...771...40B, doi:10.1088/0004-637X/771/1/40, S2CID 14911430.
4. Raghavan, Deepak; et al. (September 2010), "A Survey of Stellar Families: Multiplicity of Solar-type Stars", The Astrophysical Journal Supplement, 190 (1): 1–42, arXiv:1007.0414, Bibcode:2010ApJS..190....1R, doi:10.1088/0067-0049/190/1/1, S2CID 368553. For the adopted physical separation, see Table 13 in the appendix.
5. Gontcharov, G. A. (November 2006), "Pulkovo Compilation of Radial Velocities for 35 495 Hipparcos stars in a common system", Astronomy Letters, 32 (11): 759–771, arXiv:1606.08053, Bibcode:2006AstL...32..759G, doi:10.1134/S1063773706110065, S2CID 119231169.
6. Schröder, C.; Reiners, Ansgar; Schmitt, Jürgen H. M. M. (January 2009), "Ca II HK emission in rapidly rotating stars. Evidence for an onset of the solar-type dynamo" (PDF), Astronomy and Astrophysics, 493 (3): 1099–1107, Bibcode:2009A&A...493.1099S, doi:10.1051/0004-6361:200810377^{[permanent dead link]}
7. "84 Cet". SIMBAD. Centre de données astronomiques de Strasbourg. Retrieved 2013-10-08.
8. Holmberg, J.; et al. (July 2009), "The Geneva-Copenhagen survey of the solar neighbourhood. III. Improved distances, ages, and kinematics", Astronomy and Astrophysics, 501 (3): 941–947, arXiv:0811.3982, Bibcode:2009A&A...501..941H, doi:10.1051/0004-6361/200811191, S2CID 118577511.
9. Nakajima, Tadashi; Morino, Jun-Ichi (January 2012), "Potential Members of Stellar Kinematic Groups within 30 pc of the Sun", The Astronomical Journal, 143 (1): 2, Bibcode:2012AJ....143....2N, doi:10.1088/0004-6256/143/1/2.