Stockton Astronomical Society
Valley Skies - July 1999 Issue
Constellations:
Hercules the Strongman
Gen: Herculis
Abb: Her
Dec: +03.9° to +51.3°
RA: 15h 47m to 18h 56m
Area: 1225 sq. deg.
Hercules is a large constellation that reaches its highest point in the sky at around 10:00 PM in July. It is located just to the west of the Summer Triangle and high overhead. The torso of Hercules is the easiest part to find. It is the trapezoid composed of four stars: Epsilon (e), Zeta (z), Eta (h) and Pi (p)Herculis known as the Keystone. (A keystone is the final tapered stone fitted into an archway).
The name we have for this month’s constellation comes from Greco-Roman mythology , but it was named a bit earlier in history. This group of stars was named first by the Babylonians and later by the Greeks. To the Greeks, the constellation was originally Engonasi, or "the one who kneels". It was some time later that they changed its name to that of their hero Heracles (Roman, Hercules).
Hercules was born from the union of Zeus and a mortal woman named Alcmene. The birth of Hercules enraged the goddess Hera to the point that she sent serpents to his cradle to destroy him, but the baby Hercules strangled the serpents instead. (Those old gods didn’t set a very good example for young people!)
Hercules as a hero was involved in many, many myths not the least of which were the Twelve Labors of Hercules. Hercules was ordered to complete these twelve tasks to atone for killing his own children during a fit of rage that was caused by Hera. The stories of Hercules trials are fun to read if you get a chance.
In pictures of the constellation, Hercules is shown holding a lion skin and a club or an apple branch. The Lion skin is from his first Labor, when he defeated the Nemean Lion (the constellation Leo) and wore the skin for protection. The apple branch was from his eleventh task, where he had to get the golden apples of his stepmother Hera.
Star Hopping in Hercules
I love looking for galaxies, so the last few months have been great for me, but every body needs a change to keep things interesting. We are moving into the time of year when we look into our own Milky Way Galaxy. Here we will see more clusters and nebulas.
This month we have two beautiful globular clusters that are easy to find, one planetary nebula that is much harder to hit, and a small galaxy to keep our eyes trained.
Globular clusters are classified by the concentration of stars in their central regions, rated on a scale from 1 to 12, with 1 being the highest concentration and 12 the least.
M13 (NGC 6205) is a very large, class 5 globular cluster of perhaps 300,000 stars. Located about 23,000 light years away, it is the brightest globular in the Northern Hemisphere. To find M13, start at h Her (the northernmost star of the Keystone) and move 1/3 of the way south to z Her. When you reach this point you should easily see M13 in your finderscope. Take a long look at this cluster and you will notice strings of stars coming out of the central area. You may also notice three or four areas that appear darker, with fewer stars than the rest of the cluster.
From M13 move 40 arcminutes to the northeast to find the 11th magnitude spiral galaxy NGC 6207. This galaxy is very elongated with a bright central spot.
From p Her, the NE corner of the Keystone, move about 6° north to find NGC 6341 (M92). Use the chart to get the general location. M92 is a beautiful globular cluster, although it is a half magnitude dimmer than M13. This cluster is somewhat farther away from us than M13, but it still resolves very well in smaller scopes, showing pinpoint stars around its central core. M92 is a class 3 globular cluster.
The last object for this month is not a Messier or Hershel object. It is a small planetary nebula, NGC 6210. Use the chart and an OIII Filter to find it, about 9° south of z Her. NGC 6210 is a very bright, but small planetary that appears as a fuzzy edged disk in my 10" scope. I was unable to get any real detail out of the view but for a few seconds it appeared to have a slightly brighter outer ring, similar to M57.
If you have a larger scope, you may be able to find a cluster of galaxies in the lower right area of Hercules. These galaxies are in the Abell Catalogue and are very faint.
I will try to have a better chart for next month, with circles to hop with, until then Happy Hunting and enjoy the warm nights.
Happy Star Hopping...Eric
Copyrighted © 2000 by Stockton Astronomical Society
Lasted Updated: 11/26/2000
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