Nu1 Coronae Borealis

Nu¹ Coronae Borealis is a solitary,^[8] red-hued star located in the northern constellation of Corona Borealis. It is faintly visible to the naked eye, having an apparent visual magnitude of 5.20.^[2] Based upon an annual parallax shift of 5.02 mas,^[1] it is located roughly 650 light years from the Sun. At its distance, the visual magnitude is diminished by an extinction of 0.1 due to interstellar dust.^[9] This object is drifting closer with a radial velocity of −13 km/s.^[1]

For other stars with this Bayer designation, see ν Coronae Borealis.

ν¹ Coronae Borealis

ν1 Coronae Borealis (upper red star) in optical light
Observation data Epoch J2000.0      Equinox J2000.0 (ICRS)
Constellation	Corona Borealis
Right ascension	16h 22m 21.42283s[1]
Declination	+33° 47′ 56.5880″[1]
Apparent magnitude (V)	5.20[2]
Characteristics
Evolutionary stage	AGB[3]
Spectral type	M2 III[4]
B−V color index	1.64[4]
Astrometry
Radial velocity (Rv)	−13.01±0.12[1] km/s
Proper motion (μ)	RA: +4.756 mas/yr[1] Dec.: −38.223 mas/yr[1]
Parallax (π)	5.0245±0.0843 mas[1]
Distance	650 ± 10 ly (199 ± 3 pc)
Absolute magnitude (MV)	−1.19[4]
Details
Mass	1.2[5] M☉
Radius	80.78±2.88[6] R☉
Luminosity	1,257±70[6] L☉
Surface gravity (log g)	1.86[5] cgs
Temperature	3,828[6] K
Metallicity [Fe/H]	−0.21[5] dex
Other designations
ν1 Coronae Borealis, 20 CrB, BD+34 2773, HD 147749, HIP 80197, HR 6107, SAO 65257[7]
Database references
SIMBAD	data

This is an evolved red giant star with a stellar classification of M2 III.^[4] It is a variable star of uncertain type, showing a change in brightness with an amplitude of 0.0114 magnitude and a frequency of 0.22675 cycles per day, or 4.41 days/cycle.^[10] It has about 81 times the Sun's radius and is radiating nearly 1,300 times the Sun's luminosity from its photosphere at an effective temperature of 3,828 K.^[6]

The star ν² Coronae Borealis lies 6′ south of ν¹. ν² is also a red giant with almost the same apparent magnitude, but is a less luminous red giant branch star.^[11]