α Herculis

Alpha Herculis (Ras Algethi, 'Head of the Kneeler') is a supergiant, around 400 times the size of the Sun. It was always seen in Greek astronomy as a kneeling man, sometimes fighting with a serpent.

Alpha Herculis is most easily found by moving one binocular field northwest from alpha Ophiuchi. Alternatively drop southwest of Vega 25 (five fields): binoculars.

Alpha is a gorgeous telescopic binary, Struve 2140: 3.5, 5.4; 104, 5.0". The primary is orange and the companion blueish-green. Component B orbits the primary in a perfectly circular orbit, about every 3600 years. This component, B, is also a close binary with its companion orbiting every 52 days.

From alpha Herculis move due west two binocular fields to the solitary omega Her; from here move one field northwest to gamma and kappa: binoculars.

Gamma is a white giant with a faint optical companion; kappa also is an optical double of two yellow stars: 5.1, 6.2; 11, 25.7".

In the same field one degree north of kappa is R Herculis, a Mira-type variable whose maximum, 8.5, doesn't reach naked eye visibility.

Now move northeast a binocular field, leaving gamma Herculis in the southwest edge of your glasses: beta Herculis. Click on beta on the map for details.

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1999-2014 by Richard Dibon-Smith.