Star profile

Rasalgethi

Alpha 1 Herculis · Hercules

Variable star

3D likeness based on its real data · class M · ~3,200 K

What is Rasalgethi

Rasalgethi, «the head of the kneeling one», crowns the figure of Hercules in the deep red of its M class. It is a supergiant several times wider than the orbit of Mars and one of the broadest variables in the sky: its brightness breathes over months as its huge atmosphere pulses in slow waves. Its light crosses 359 light years to reach earthly telescopes.

Where it is and when to see it

Rasalgethi lies in the northern celestial hemisphere. It is visible to the naked eye under a dark sky. Its best month of the year is June, when it culminates around midnight.

From London it culminates about 53° above the horizon.
From New York it culminates about 64° above the horizon.
From Sydney it culminates about 42° above the horizon.

It can be seen from anywhere north of 76° S.

It ranks no. 2 in brightness among the 136 stars of Hercules in our catalogue. To find it, start from Kornephoros, the brightest: it lies about 13° away (a fist at arm's length covers about 10°).

The light you see today left it about 360 years ago.

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Astronomical data for Rasalgethi

Constellation: Hercules
Apparent magnitude: 2.78
Distance: 359.6 light years
Coordinates (J2000): RA 258.662° · Dec 14.390°
Catalogue: HIP 84345 · HD 156014

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Other stars in Hercules

Hercules has 136 stars in Stelvia's catalogue. Here are a few of them.

See all 136 stars in Hercules