Stars in Hercules
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Stars in Hercules |
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Stars in Hercules | M13 | M92 | NGC 6058 | NGC 6210 | NGC 6229 Stars in Lyra | M56 | M57 | NGC 6791 
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Alpha Herculis is also known by a proper name, Ras Algethi, which means "Head of the kneeler"; this star marks the head of Hercules, whose body is drawn with south being up. Just a few degrees to the southeast, the slightly brighter Ras Alhague in Ophiuchus can be distinguished by its white color - the lead star of Hercules is deep orange. A red giant sun, Ras Algethi puts out more than seven thousand times as much light as our sun, and this amount varies; Ras Algethi oscillates in an irregular period, and may appear as much as a magnitude off it's average brightness. Also of interest, telescopic observers will find a 5th magnitude bluish companion star just 4.6 arc seconds from Ras Algethi. The color contrast is impressive, and while a fairly close pair, this is worth investigating. A true binary system, these stars are at least 200 times farther apart than Pluto is from the sun - the orbital period must be many thousands of years.
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Delta Herculis, also known as Sarin, is located just southeast of the "keystone" pattern of Hercules, and shines at 3rd magnitude. A moderately nearby star at 75 light years, Sarin boasts a "companion" star of the optical variety - that is, it only LOOKS like a companion. The 8th magnitude star about 15 arc seconds from Sarin is seen only in line of sight - these stars have no real connection with one another, and the separation is opening steadily as they proceed on their very separate ways.
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Zeta Herculis is a very close and difficult binary star, but of particular interest as it is only 30 light years away, and the stars involved are not terribly unlike our sun. The magnitudes of the stars are 2.8 and 5.5, both easily seen in small telescopes, but they are only half of one arc second apart! This separation, which actually amounts to about five times the Sun-Earth distance, widens out to three times as much on the other half of the 34.8-year orbital cycle. The brighter of the stars is about 6 times as luminous as the sun and shines with a faintly yellowish light. The fainter star is only half as bright as ours, and is distinctly amber in color.
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Mu Herculis is a noted triple star, although in smaller instruments will at first seem to be a double - magnitudes 3.42 and a much fainter 9.8 at 34 arc seconds separation. Careful observation will reveal that this dim companion is two stars with just 1.36 arc seconds between. The bright primary of the system is a yellow subgiant three times as luminous as the sun; both faint companions are red dwarf stars, roughly 200 times less brilliant than our sun. Mu Herculis is a near neighbor of the sun, at just 30 light years away.
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