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)	+3.1m to +3.9 | +5m to +7m
Absolute magnitude
Physical characteristics
Mean Diameter (dS = 1,392,000 km)	560,000,000 km | ~ 402.3 dS 3.74 AU
Surface area
Volume
Mass
Relative mass to the Sun (mS = 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 (LS = 3.827 × 1026 J s-1)
Orbital characteristics
Period of rotation
Period