Tau Cancri

Tau Cancri is a solitary,^[4] yellow-hued star in the zodiac constellation of Cancer. Its name is a Bayer designation that is Latinized from τ Cancri, and abbreviated Tau Cnc or τ Cnc. With an apparent visual magnitude of +5.42,^[2] it is faintly visible to the naked eye. Based upon an annual parallax shift of 12.03 mas as seen from Earth,^[1] it is located around 272 light-years (83 pc) from the Earth. The star is drifting closer to the Sun with a line of sight velocity of −14 km/s.^[5]

Tau Cancri

Observation data Epoch J2000.0      Equinox J2000.0 (ICRS)
Constellation	Cancer
Right ascension	09h 08m 00.050s[1]
Declination	+29° 39′ 15.24″[1]
Apparent magnitude (V)	+5.42[2]
Characteristics
Evolutionary stage	red clump[3]
Spectral type	G8 III[4]
U−B color index	+0.57[2]
B−V color index	+0.89[2]
Astrometry
Radial velocity (Rv)	−13.90±0.14[5] km/s
Proper motion (μ)	RA: −32.199 mas/yr[1] Dec.: +2.640 mas/yr[1]
Parallax (π)	12.0346±0.1007 mas[1]
Distance	271 ± 2 ly (83.1 ± 0.7 pc)
Absolute magnitude (MV)	+0.81[6]
Details[5]
Mass	2.42±0.09 M☉
Radius	7.76±0.51 R☉
Luminosity	40 L☉
Surface gravity (log g)	3.21 cgs
Temperature	5,153 K
Metallicity [Fe/H]	−0.06 dex
Rotational velocity (v sin i)	1.95±0.45 km/s
Age	620±60 Myr
Other designations
τ Cnc, 72 Cancri, BD+30°1817, FK5 2719, HD 78235, HIP 44818, HR 3621, SAO 80650[7]
Database references
SIMBAD	data

With an age of about 620^[5] million years and a stellar classification of G8 III,^[4] this is a red-clump giant star,^[3] which indicates that it has evolved onto the horizontal branch and is generating energy through helium fusion at its core. It is a microvariable, showing a luminosity variation of 0.04 in magnitude.^[8] Tau Cancri has an estimated 2.4 times the mass of the Sun and 7.8 times the Sun's radius. The star radiates 40 times the solar luminosity from its photosphere at an effective temperature of 5,153 K.^[5] It is spinning slowly with a projected rotational velocity of 2 km/s.^[5]