Jimmy Westlake: Scorpius livens up the summer sky
There aren’t many constellations that resemble the objects or creatures for which they are named. Scorpius, the Scorpion, is a delightful example of one that does. This celestial scorpion scurries across our southern sky on summer evenings, so this month is prime time for scorpion hunting.
As soon as it gets dark in the evening, step outside and face south. This year, the southern sky is dominated by two bright planets. Mars is the brighter of the two, and Saturn the fainter.
Below these two temporary visitors to the area is a bright, flashy, red star named Antares, which represents the heart of the Scorpion. Antares literally means “the Rival of Mars,” so named because its blood-red color reminded ancient sky watchers of the red planet Mars (or Ares).
This year offers a rare opportunity to compare the colors of Mars and Antares, almost side by side. Which one do you think looks redder?
This is also a great opportunity to see for yourself that stars twinkle and planets don’t. Look closely at Mars and Saturn. Their light is very steady — no flickering or flashing. Now look at Antares. It twinkles like crazy.
The twinkling of starlight is caused by air currents and temperature differences in the Earth’s atmosphere. The light from a star arrives at Earth as a single point, due to its enormous distance, but planet-light arrives as a bundle of many points of light because the planets are relatively nearby. As a result, the atmosphere has a greater twinkling effect on the starlight than on the planet-light.
From the Scorpion’s Alpha star, Antares, trace out a line of fainter stars down to the lower left that curls up on the end, like a giant fishhook. This is the Scorpion’s tail, marked at its tip by the deadly stinger stars, Shaula and Lesath.
To the right of Antares, you’ll spot a vertical trio of stars, reminiscent of Orion’s belt of winter. The middle star, Dschubba, represents the Scorpion’s head, and the two stars on either side mark his pincers.
In Greek mythology, Scorpius is notorious for stinging and killing Orion, the Hunter. The legend tells us that Orion once made the boast that he could kill every living creature on Earth, if he wanted to. The animals got together and decided they must make a preemptive strike, just in case Orion was serious.
They chose one of their smallest members, the scorpion, to teach Orion a deadly lesson. Stalking the hunter one day in the woods, the scorpion stung Orion on the heel. The great hunter wheeled around in pain and collapsed from the scorpion’s fatal poison.
The hunter and the scorpion were both immortalized in the stars as our constellations of Orion and Scorpius, but they were placed on opposite sides of the sky so that the two mortal enemies could never be seen at the same time. Scorpius appears low in our mid-summer sky, while Orion rides high in the mid-winter sky.
In Hawaiian mythology, the stars of Scorpius represent the magic fishhook of the demigod Maui. One day, while fishing in the Pacific Ocean, Maui accidentally snagged the ocean floor with his hook and inadvertently yanked up the Hawaiian Islands.
Scorpius has many treats for binocular observers. Take a close-up look at the two stars marking the scorpion’s stinger, Shaula and Lesath. You’ll see why they have earned the nickname “the Cat’s Eyes.”
A line drawn through these two stars to the left (east) points to a fuzzy patch of light that, through binoculars, is resolved into a beautiful cluster of glittering stars called M7, or Ptolemy’s Cluster. Look for the smaller Butterfly Star Cluster, M6, just above M7.
And, don’t ignore spectacular Antares. This red supergiant star becomes a glowing red ember, when seen through binoculars. Just to the right (west) of Antares, you can spot another buzzing beehive of stars, the Cat’s Eye Cluster, M4.
Whether you imagine a scorpion or a fishhook in these stars, this constellation will quickly become one of your summertime favorites.
Professor Jimmy Westlake teaches astronomy and physics at Colorado Mountain College’s Alpine Campus. His “Celestial News” column appears weekly in the Steamboat Today newspaper. Check out Jimmy’s astrophotography website at http://www.jwestlake.com.
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