The mighty Hercules, an extraordinary strong man of Greek mythology, is represented in tonight’s evening sky, doing a mighty balancing act.
Hercules, the constellation, is depicted with one of the grandest globular clusters sitting on its head. Part of the folklore of the ancient Greeks has Hercules tricking Atlas in putting the entire sky- the Celestial Sphere back on his shoulders. Without a telescope, the ancient Greeks would not have known their hero put into the sky was doing such a mighty act of his own, holding a vast star city on his noggin.
How you see Hercules or any other constellation depends on the star charts you look at. Each of the 88 constellations are defined by set boundaries recognized internationally. Within each boundary on sky maps are the host of stars appearing in that direction; only the handful of brighter stars among them trace the imaginative stick-figure we commonly see on star charts. These stick-figures, like a child’s “connect-the-dot” picture, don’t always well resemble the subject of the constellation.
Some star map makers manage to come close, and probably leading them all is the late H.A. Rey, who with his wife Margret was the author and illustrator of children’s books including the famed Curious George series. He also came out in 1952 with a landmark astronomy book, The Stars a New Way to See Them, which has served sky watchers of all ages for generations. Often employing fainter stars, Rey’s depictions amazingly picture the constellations so they actually look like what they are supposed to be.
Hans Augusto Rey lived, 1898-1977.
Hercules is one of them. The way Rey drew the lines, four of the principal stars becomes the mythological Hercules’ head. Situated right on top is the globular cluster M13, faintly visible to the unaided eyes from a dark site, and easily seen as a small, fuzzy spot with binoculars.
Be sure the Moon is not around, to wash out all but the brighter stars and planets. The sight of M13 in at least a four inch telescope, is most interesting. Low magnification will show a fuzzy disc, and higher power will resolve the “fuzziness” into a great ball of stars. It appears most concentrated in the center, with the edge breaking up into streams of faint stars leading away from the middle. It is even better in a larger aperture telescope- such as a reflector with a main mirror six inches across.
There is also another bright globular cluster in Hercules, M92, although it not as well known. The cluster does not happen to be close to the brighter stars of Hercules for easy location.
Globular clusters are immense spheres of stars, bound by their common gravity, which orbit a galaxy. There are about 158 known globulars circling the Milky Way. M13 has an estimated several hundred thousand stars and are contained within a span of about 145 light years.
The four stars marking the “head” of Hercules is also known as the “Keystone” due to the shape you can trace connecting them.
Seven stars in Hercules are known to have planets. One of them is visible in binoculars, 14 Herculis (magnitude 6.6).Sixth magnitude is normally the faintest you can detect without optical aid on a dark night.
An interesting naked eye star is Alpha Herculis, which is red in color and varies in brightness irregularly, from 3rd to4th magnitude. This star is also known as Ras Algethi. Telescope users will enjoy splitting this star into its two components. A double star system, the fainter companion star appears greenish.
Hercules is among good company. On mid-June evenings, look for the constellation high in the east. Right above it is Bootes, the kite-shaped constellation ending in blazing orange Arcturus- high in the south. Just below Hercules, about half way up in the east will be bright blue-white Vega, the luminary marking the parallelogram Lyra constellation. Go left towards the north, and you will see the four stars marking the head of Draco the Dragon. Lower right of Hercules, in the southeast, is the good doctor of the sky, the sprawling constellation Ophiuchus, a mythological physician. Sandwiched between Hercules and Bootes- between the “keystone” of Hercules and the star Arcturus, is the marvelous half-circle of stars, Corona Borealis, the Northern Crown. Its brightest “gem” is the star Gemma.
Full Moon is on June 18th. After that, the Moon rises later and later each evening, giving a widening “window” of dark starry skies. Meanwhile, enjoy the beautiful Moon and the many stars that still are visible.
Keep looking up!