The Scorpion crawls over the southern horizon

By Bob Moler

Scorpius and Libra from the Grand Traverse Region at 11 pm, July 15th. It also shows the location of the globular cluster M4. The funny squiggle () near the South cardinal point is the Greek letter zeta. Near that star is an interesting star field for those who travel far enough south. Credit: Stellarium.

Low in the south on July evenings can be found a constellation that represents a creature that’s better appreciated in the sky than in person. The stars portray a scorpion, which astrologers call Scorpio and astronomers call Scorpius. Luckily, around here, Scorpius is as close as we’ll get to the real thing.

The stars in this constellation really do exhibit the scorpion’s characteristic curved tail complete with the poisonous stinger at the end. The chart above shows the lines between the stars that suggest a scorpion, especially its tail. The Arabs, apparently extended it to Libra the scales to the right. As a matter of fact the northernmost star of Libra is called Zubeneschamali which means Northern Claw. The star in Libra to the far right is Zubenelgenubi (one of the great sounding star names), which means Southern Claw.

In mythology Scorpius killed Orion with his stinger. The proof of this is that Orion flees the sky to the west in the late spring as the scorpion rises in the southeast. In other myths Orion meets his end in other ways.

Scorpius’ brightest star is Antares, whose name means Rival of Mars. It is a red giant star whose color is nearly identical to the Red Planet. When Mars passes through northern Scorpius someone who didn’t know the constellations would be hard put to tell them apart. Mars passes through here every two years.

Antares is a huge star which lies low in the south at its highest. Its brightness is magnitude 1.05 which varies a bit in an irregular way, as some red giant stars do. Its appearance to the unaided eye, binoculars, and telescope is greatly affected by the steadiness of the atmosphere. Lying low in the sky, due to its southerly position on the celestial sphere and our location on the northerly part of the earth means we are always looking at it through the thickest parts of the Earth’s atmosphere. Antares twinkles merrily and changes colors to the unaided eye. In binoculars it appears to jump around and change colors. In telescopes it can appear like a multicolored sparkler spitting and sputtering all the colors of the rainbow. Consequently it results in more than a few UFO calls.

Antares also has a dim companion star that appears green probably in contrast to the red of it’s primary star. Compared to Antares 1.05 magnitude, the companion is 6.5 magnitude. It is difficult to spot. I’ve never seen it, though it would lie in the sparkler effect of the atmosphere on Antares itself.

A note on magnitudes: The magnitude scale is roughly based on the 6 magnitudes of the Greek astronomer Hipparchus of the 2nd century BC. He invented a scale where the brightest stars are first magnitude and the faintest visible to the unaided eye are 6th

Modern astronomers have created a mathematical basis for the magnitude scale where each magnitude step is a factor of 2.512 times brighter of dimmer. Five magnitudes is a difference of 100 in brightness. In keeping with Hipparchus’ scale the brighter the star the lower the magnitude. The Sun has a magnitude of about -26, while the faintest stars visible in telescopes is currently around +30.

The brightest star cluster in Scorpius is M4 near Antares. Its brightest stars are 10th magnitude, though most are 13th and dimmer. So a few of the stars of the star cluster may be visible in relatively small telescopes.

The remarkable star field above Zeta Scorpii as it might appear in binoculars. Not really, the binocular view is much better! This is an image from Stellarium. I don't recall if I saw the nebulosity.

Another neat area to view in binoculars is around Zeta (z) Scorpii. On the chart above it’s near the top of the S for south symbol. It is actually a wide double star, as is the star on the chart above it. Here is a wonderful cluster of stars. I first noticed this on a trip to the Florida Keys in 1986 to view Halley’s Comet. From there, Scorpius rides a lot higher in the south than it does here. From here, on a crystal clear night and a very low southern horizon, we just get a hint of its glory.

The above objects are just a hint of the wonders that are located in Scorpius on a clear summer night.

Scorpius as Nenabozho with bow and arrow. Constellation art embedded in Stellarium. Art source is “Ojibwe Giizhig Anung Masinaaigan, Ojibwe Sky Star Map” by A. Lee, W. Wilson, C. Gawboy, J. Tibbetts.

The Anishinaabe people, who came to the great Lakes area some time before the Europeans from the north and east would probably have never seen a scorpion, so it didn’t occur to them to see it as such. The constellation, to them was Nenabozho, a great hero who made many great journeys. The arc of three stars at the right of Scorpius is part of his bow, as he appears to shoot an arrow toward Curly Tail, the Great Underwater Panther made of the Sickle asterism of Leo and the head of Hydra. I learned of him in the The Mishomis Book – The Voice of the Ojibway by Edward Benton-Banai. He calls him Original Man, or Anishinabe or Waynaboozhoo.

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Updated: 08/04/22