Hercules is a northern constellation with a mythology that goes back 4,500 years to ancient Sumerian times. It is named after the Roman mythological hero Hercules, who was a version of the Greek hero Heracles. Hold your mouse cursor over the image to see constellation figures, boundaries, and star identifications. Hercules contains the distinctive Keystone asterism, seen in the center of this image, that lies one-third of the way from Vega to Arcturus. The Keystone is comprised of the four bright stars Zeta Herculis (magnitude 2.81, 35.0 light-years distant), Pi Herculis (magnitude 3.16, 374.9 light-years distant), Eta Herculis (magnitude 3.48, 108.7 light-years distant) and Epsilon Herculis (magnitude 3.92, 155.3 light-years distant). Alpha Herculis is Rasalgethi, a spectral-class M semi-variable red-giant star whose brightness varies from a maximum apparent magnitude of 2.74 to a minimum magnitude of 4.0. It is located 380 light-years away near the border of Ophiuchus, 5.25 degrees west-northwest of second magnitude Rasalhague, Alpha Ophiuchi. In Arabic Rasalgethi means the "Head of the Kneeler." Rasalgethi is also a colorful multiple star system with a 5.4 magnitude secondary companion separated by 4.84 arcseconds. The secondary star is itself a binary star with a primary G-type yellow-giant and a secondary F type yellow-white dwarf star companion. The brightest star in the constellation of Hercules is Kornephoros (Beta Herculis), which is a spectral-class G star that shines at magnitude 2.8 and is located 139.4 light-years away. In Greek, Kornephoros means the "Club Bearer." Hercules lies away from the Milky Way so it doesn't contain any prominent bright or dark nebulae, but it does contain the spectacular globular cluster M13, as well as galaxy cluster Abell 2151. Hercules was cataloged by the Greek astronomer Ptolemy in the second century C.E. (Common Era). It is the fifth largest of today's 88 modern constellations, covering 1,225 square degrees of sky. North is to the left in the above image.
|
||||||||||
|
