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Ras Algethi, Alpha1 Herculis, 64 Herculis

Proper NamesRasalgethi, Ras Algethi
Bayer DesignationAlpha1 Herculis
Flamsteed Number64 Herculis
HR (BSC)6406
Right Ascension17h 14m 39s
Declination+14° 23' 25"
Distance382 light years
117 parsecs
MagnitudeApparent: +3.3
Absolute: -2.0
Spectral ClassM5 Red Supergiant
Optimum VisibilityJune / July
NotesThe primary star of the Ras Algethi system is a swollen red giant with a diameter some four hundred times that of the Sun, which pulsates in a semiregular pattern and shows considerable variability over time. It is part of a triple system, orbited at a distance of some 500 AU by a binary pair consisting of a yellow giant and a bright yellow dwarf star.

The brightest star in Hercules has an Arabic name meaning 'head of the kneeling man'. The primary in this distant and complex system is a very massive red giant, but orbiting this is a closer double star that shines with a yellow-green light.


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