Ras Algethi

Ras Algethi (Arabic Rasalgethi from Ra`s al-Jathi a Head of the kneeling one) (α 1 Herculis | 64 Herculis) is a double star system with a primary massive red giant star and a closer companion.

Physical and other characteristics

Ras Algheti is the 4th largest star known to us, circa 720 times greater than the Sun.

Observation data

Semiregular Variable, type SR c

Right ascension (RA, α) (J2000,00) 17 h 14 m 38.80 s

Declination (Dec, δ) (J2000,00) +14° 23' 25.0"

Distance from Earth 550 LY | (169 pc)

Visual brightness (V) +3.1^m to +3.9 | +5^m to +7^m

Absolute magnitude

Physical characteristics

Mean Diameter (d_S= 1,392,000 km) 560,000,000 km | ~ 402.3 d_S
3.74 AU

Surface area

Volume

Mass

Relative mass to the Sun
(m_S= 1.9891 × 10³⁰ kg)

Density

Surface gravity

Spectral type M5 Ib-II (Red Super Giant)

Surface temperature

Age

Color (B-V) (Orange-red | Bluish-green)

V-I

Luminosity (L_S = 3.827 × 10²⁶ J s^-1)

Orbital characteristics

Period of rotation

Period

Observation data
Semiregular Variable, type SR c
Right ascension (RA, α) (J2000,00)	17 h 14 m 38.80 s
Declination (Dec, δ) (J2000,00)	+14° 23' 25.0"
Distance from Earth	550 LY \| (169 pc)
Visual brightness (V)	+3.1^m to +3.9 \| +5^m to +7^m
Absolute magnitude
Physical characteristics
Mean Diameter (d_S= 1,392,000 km)	560,000,000 km \| ~ 402.3 d_S 3.74 AU
Surface area
Volume
Mass
Relative mass to the Sun (m_S= 1.9891 × 10³⁰ kg)
Density
Surface gravity
Spectral type	M5 Ib-II (Red Super Giant)
Surface temperature
Age
Color (B-V)	(Orange-red \| Bluish-green)
V-I
Luminosity (L_S = 3.827 × 10²⁶ J s^-1)
Orbital characteristics
Period of rotation
Period