V Coronae Borealis

V Coronae Borealis (V CrB) is a Mira-type long period variable star and carbon star in the constellation Corona Borealis. Its apparent magnitude varies between 6.9 and 12.6 over a period of 357 days.^[2]

V Coronae Borealis

V Coronae Borealis in optical light
Observation data Epoch J2000      Equinox J2000
Constellation	Corona Borealis
Right ascension	15h 49m 31.31093s[1]
Declination	+39° 34′ 17.9111″[1]
Apparent magnitude (V)	6.90[1]
Characteristics
Spectral type	C6,2e(N2e)[2]
Astrometry
Distance	630 pc[3]
Details[3]
Radius	750[a] R☉
Luminosity	5300 L☉
Temperature	1800 K
Database references
SIMBAD	data

The visual band light curve of V Coronae Borealis, from AAVSO data^[4]

V Coronae Borealis is too far from Earth for its parallax to be measured effectively. Basing on a period of 357 days, the absolute magnitude of V Coronae Borealis has been calculated to be -4.62.^[5] It is estimated to be 630 pc (2,100 ly) from Earth, has a luminosity of 5,300 L_☉ and a rather cool effective temperature of 1,800 K, these implying a very large radius of about 750 R_☉, making V Coronae Borealis one of the largest stars so far discovered.^[3] If placed in the center of the Solar System, its size would engulf all rocky planets and reach parts of the asteroid belt.

Notes

1. Applying the Stefan–Boltzmann law with a nominal solar effective temperature of 5,772 K:

   ${\displaystyle {\sqrt {(5772/1800)^{4}*5,300}}=750\ R\odot }$