Rho Persei

Rho Persei, Latinized from ρ Persei, is a star in the northern constellation of Perseus. It has the traditional name Gorgonea Tertia /ɡɔːrɡəˈniːə ˈtɜːrʃə/,^[11] being the third member of the quartet called the Gorgonea in reference to the Gorgons from the legend of Perseus.^[9] An apparent visual magnitude of +3.39^[2] makes it visible to the naked eye, but a challenge to view from a well-lit urban environment. Based upon parallax measurements, it is located at a distance of roughly 308 light-years (94 pc) from Earth.^[1]

A visual band light curve for Rho Persei, plotted from AAVSO data^[12]

ρ Persei

Location of ρ Persei (circled)
Observation data Epoch J2000      Equinox J2000
Constellation	Perseus
Right ascension	03h 05m 10.59385s[1]
Declination	+38° 50′ 24.9943″[1]
Apparent magnitude (V)	+3.39[2]
Characteristics
Evolutionary stage	AGB[3]
Spectral type	M4 II[4]
U−B color index	+1.79[2]
B−V color index	+1.65[2]
Variable type	SRb[4]
Astrometry
Radial velocity (Rv)	+29.10±0.30[5] km/s
Proper motion (μ)	RA: +129.22[1] mas/yr Dec.: –105.70[1] mas/yr
Parallax (π)	10.60±0.25 mas[1]
Distance	308 ± 7 ly (94 ± 2 pc)
Absolute magnitude (MV)	−1.7[6]
Details[7]
Mass	1.9±0.7 M☉
Radius	143±12 R☉
Luminosity	2,692+192 −180 L☉
Surface gravity (log g)	0.37±0.15 cgs
Temperature	3,479±125 K
Metallicity [Fe/H]	−0.15 dex
Rotational velocity (v sin i)	11.2[8] km/s
Age	440[9] Myr
Other designations
Gorgonea Tertia, Rho Per, ρ Per, 25 Persei, BD+38°630, FK5 109, GC 3682, HD 19058, HIP 14354, HR 921, SAO 56138, PPM 68074[10]
Database references
SIMBAD	data

Johann Schmidt discovered that Rho Persei is a variable star, in 1854.^[13][14] Rho Persei is a semiregular variable star, whose apparent magnitude varies between 3.3 and 4.0^[15] with periods of 50, 120 and 250 days.^[6] The star has reached the asymptotic giant branch of its evolution.^[3] It is a bright giant star with a stellar classification of M4 II.^[4] The outer envelope has an effective temperature of 3,479 K,^[7] giving it the red-orange hue of an M-type star.^[16]

This star has a mass 1.9 times the mass of the Sun, while its radius has expanded to 143 times solar. It is radiating some 2,700 times the Sun's luminosity.^[7] Rho Persei is losing mass at the rate of 1.2×10⁻⁸ solar masses per year, or the equivalent of the Sun's mass every 83 million years.^[17] It is about 440 million years in age.^[9]

Naming

In Chinese, 大陵 (Dà Líng), meaning Mausoleum, refers to an asterism consisting of ρ Persei, 9 Persei, τ Persei, ι Persei, κ Persei, β Persei, 16 Persei and 12 Persei. Consequently, the Chinese name for ρ Persei itself is 大陵六 (Dà Líng liù, English: the Sixth Star of Mausoleum.).^[18]