28 Cancri

28 Cancri is a star system in the zodiac constellation of Cancer. It is a variable star with the designation CX Cancri, and is close to the lower limit of visibility with the naked eye, having a mean apparent visual magnitude of 6.05.^[3] The annual parallax shift seen from Earth's orbit is 8.5 mas, which provides a distance estimate of about 384 light years. It is moving away from the Sun with a radial velocity of around +9 km/s.^[6]

28 Cancri

A light curve for CX Cancri, plotted from TESS data[1]
Observation data Epoch J2000      Equinox J2000
Constellation	Cancer
Right ascension	08h 28m 36.78530s[2]
Declination	+24° 08′ 41.7179″[2]
Apparent magnitude (V)	6.05[3]
Characteristics
Spectral type	F0 Vn[4]
U−B color index	+0.13[3]
B−V color index	+0.22[3]
Variable type	δ Sct[5]
Astrometry
Radial velocity (Rv)	+9.0±4.3[6] km/s
Proper motion (μ)	RA: −30.946[2] mas/yr Dec.: −39.719[2] mas/yr
Parallax (π)	8.4885±0.1539 mas[2]
Distance	384 ± 7 ly (118 ± 2 pc)
Absolute magnitude (MV)	0.41[7]
Details
Mass	2.36±0.11[8] M☉
Radius	3.7[2] R☉
Luminosity	44[2] L☉
Surface gravity (log g)	3.61[2] cgs
Temperature	7,516+52 −103[8] K
Metallicity [Fe/H]	+0.16[9] dex
Rotational velocity (v sin i)	133[8] km/s
Age	737[2] Myr
Other designations
28 Cnc, CX Cnc, BD+24°1931, HD 71496, HIP 41574, HR 3329, SAO 80204[10]
Database references
SIMBAD	data

Based upon proper motion variation, this is an astrometric binary system with high likelihood (99.8%).^[11] The visible component has a stellar classification of F0 Vn,^[4] indicating it is a F-type main-sequence star with "nebulous" lines due to rapid rotation.

In 1973, John R Percy announced that 28 Cancri might be a variable star.^[12] Stephen John Horan et al. confirmed that the star's brightness varies, in 1974.^[13] In 1979, it was given its variable star designation.^[14] It is a Delta Scuti variable star with a period of 0.0960 days and an amplitude of 0.020 in magnitude.^[15] With 2.4 times the mass of the Sun it is spinning with a high projected rotational velocity of 133 km/s. 28 Cancri is radiating roughly 44 times the Sun's luminosity from its photosphere at an effective temperature of around 7,516 K.