R Cassiopeiae

Not to be confused with Rho Cassiopeiae.

R Cassiopeiae is a variable star in the northern constellation of Cassiopeia. It is located approximately 570 light years distant from the Sun, but is drifting closer with a radial velocity of −23 km/s.^[6] This is a pulsating Mira-type variable star with a brightness that varies from magnitude +4.4 down to +13.5 over a period of 433.6 days.^[4] At its maximum brightness, R Cassiopeiae is visible to the naked eye as a faint, red-hued star.

R Cassiopeiae

The visual band light curve of R Cassiopeiae, from AAVSO data[1]
Observation data Epoch J2000.0      Equinox J2000.0
Constellation	Cassiopeia[2]
Right ascension	23h 58m 24.868s[3]
Declination	+51° 23′ 19.71″[3]
Apparent magnitude (V)	4.4 to 13.5[4]
Characteristics
Spectral type	M6e–M10e[4]
U−B color index	+0.08[5]
B−V color index	+1.83[5]
Variable type	Mira[4]
Astrometry
Radial velocity (Rv)	−22.94±0.72[6] km/s
Proper motion (μ)	RA: 82.847[3] mas/yr Dec.: 17.485[3] mas/yr
Parallax (π)	5.7423±0.2011 mas[3]
Distance	570 ± 20 ly (174 ± 6 pc)
Details
Mass	0.59[7] M☉
Radius	263[7] R☉
Luminosity	8,960[8] L☉
Surface gravity (log g)	−0.50[9] cgs
Temperature	2,812[7] K
Metallicity [Fe/H]	0.50[9] dex
Other designations
R Cas, BD+50°4202, HD 224490, HIP 118188, HR 9066, SAO 35938, ADS 17135, CCDM J23584+5123[10]
Database references
SIMBAD	data

Norman Robert Pogson discovered the star, in 1853.^[11][12] This aging red giant star has a stellar classification that varies from M6e to M10e,^[4] where the 'e' suffix indicates emission features in the spectrum. Currently on the asymptotic giant branch,^[13] it has 59%^[7] of the mass of the Sun with an oxygen rich chemical abundance.^[14] Having exhausted the supply of hydrogen at its core, the star has expanded to 263^[7] times the Sun's radius. On average, the star is radiating 3,837^[7] times the luminosity of the Sun from its swollen photosphere with an effective temperature ranging around 2,812 K.^[7] It is losing mass at the rate of 1.3×10⁻⁶ M_☉/yr^−1[8] and is surrounded by a dusty circumstellar shell that extends out to 2.8′.^[14]

See also

• S Cassiopeiae
• PZ Cassiopeiae
• TZ Cassiopeiae