Stockton Astronomical Society
Valley Skies - July 1998 Issue
Constellations:
Scorpius - the Scorpion
Gen: Scorpii
Abb: Sco
Dec: -8.1° to -45°
RA 15hr 44min to 17hr 55min
Scorpius is the 8th constellation in the zodiac and, like Libra, it lies south of the celestial equator. Using 10 P.M. as a reference, Scorpius rises in the east in May, reaches it highest point in July, then fades in the west during August. With the scorpion crawling through our view to the core of the Milky Way Galaxy, he is loaded with objects to see and explore.
Scorpius is one of the few constellations that looks like what it is called, making it easy to locate in the sky. From its claws (that were much longer prior to Julius Caesar, who ordered that they be part of a new constellation to be called Libra) to it’s long hooked tail, catching almost a dozen clusters in its arc, Scorpius is well named. It even has a heart, the star Antares (named by the Greeks, meaning the "rival to Mars") that shines a very real red in the middle of the scorpion. Although it closely resembles a scorpion, the Egyptians also viewed it as a serpent and even today some see it as a kite.
The Scorpion appears in at least two legends with the great hunter Orion. In the first legend, Mother Earth sent the armored and poisonous scorpion to kill Orion, after he boasted that he could kill any beast. But Orion was unable to kill the scorpion and the scorpion was placed 180° behind him in the sky to stalk the hunter throughout all eternity.
The second legend revolves around Greek mythology and Apollo, who plotted to keep Orion away from his sister Artemis by having the scorpion chase Orion into the sea. Both of these legends could have been used to explain why every time Scorpius starts to rise in the east Orion would be gone in the west.
Exploring in Scorpius
We start our star hops this month at the heart of the constellation. Antares (21 a Scorpii) is a very red and large binary (700 times the size of our sun). It is also a variable that fluctuates from magnitude 0.88 to 1.80 every 1733 days. Its companion is a 5.4 magnitude green star that is almost impossible to see in the glare from the primary. The reflection nebula IC 4606 encircles Antares, but is far too faint for me to pick out of the glare. About 1½° west of Antares is NGC 6121 (M4), a globular cluster with a rather loose central core. This cluster contains about 10,300 stars, with a magnitude of 5.93.
From M4, move to the wide double, 20 Sigma (s) Scorpii. This double was known to the Arabs as Al Niydt and represented the blood vessels coming out of the heart. Visually this is the next bright star to the east-northeast of Antares. From here move 1° north to 19 Omicron (o) Scorpii. This star leads us to the globular cluster NGC 6093 (M80). Although this cluster is not real impressive in appearance it does have one feature that makes it special. In 1860 Dr. Auwers discovered a nova near its center (T-N1860) and for a few day the star was as bright as magnitude 7.
The head and claws of Scorpius are made up of many multiple star systems and very faint reflection nebulas that are fun to look at, but we will continue our hops back at Antares. Travel 8° east of Antares to the class 8 globular cluster NGC 6273 (M19). This cluster is actually in Ophiuchus but I find it from Scorpius. The core of M19 is oval shaped and very open, making it easier to resolve many stars close to the core.
About 4 degrees south of M19 is the class 4 globular cluster NGC 6266 (M62).
This asymmetrical cluster is located on the border of Scorpius and Ophiuchus
and contains a large number of RR Lyrae type Variables. These stars are
pulsating during periods that range from 0.2 to 1.2 days and were formerly
known as short period Cepheids. Most stars of this type are found in
globular clusters.
Back to Antares. Traveling southeast, the next bright star is 23 Tau (t) Scorpii, then farther down the spine is 26 Epsilon (e) Scorpii that marks the start of the scorpions tail. Move 3° south to the next bright star, Mu (m) Scorpii: this is actually m1 and m2 Scorpii, an eclipsing binary system.
2½° east of m Scorpii is the open cluster NGC 6281. This cluster is estimated to be 220 million years old and contains about 30 stars. Back to m Sco. Hop 1½° south-southeast to another open cluster, NGC 6242, that is larger but fainter than NGC 6281. 1° south is Harvard 12, a rather poor open cluster surrounded by a very faint emission nebula. At the very least you will need a nebula filter and a large aperture to see it.
This area is a real good place to scan with binoculars as the galactic equator cuts right through it and the rich Milky Way star fields are beautiful to look at. Just south of H 12 is NGC 6231, an open cluster with about 120 stars nestled in another area of nebulosity.
From NGC 6231 jump over to the stinger made up of Upsilon (u) Scorpii to the west and Lambda (l) Scorpii to the east. Use these two stars to guide you 4° to the northeast to find NGC 6475 (M7), an open cluster that is very large and bright. This is the southern most object on Messier’s list and was added to it on May 23, 1784.
3½° northwest of M7 is NGC 6405 (M6) the Butterfly cluster. This cluster is estimated to be 100 million years old and sort of looks like a butterfly - maybe. It is very loose and contains about 80 stars.
I am going to stop here before the postman won’t deliver this newsletter, but there are so many more things to find in this constellation. Be sure to set many nights aside to explore all of it’s wonders before it slips away in the west.
Happy Star-Hopping...Eric Reichenbach
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Lasted Updated: 11/26/2000
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