By Mike Lynch
One of my favorite constellations is Scorpius the Scorpion because it’s one of the few constellations that actually looks like what it’s supposed to be.
The only trouble with it is that in Northwest the great scorpion never gets all that high in our sky. Stargazers in the southern half of the U.S. have a better view of Scorpius, as the celestial beast takes a much higher track in the sky.
Nonetheless, even in more northern latitudes Scorpius is still a great attraction in the summer sky. It lies within the Milky Way band, that ribbon of light that cuts the entire sky in half this time of year.
The Milky Way band basically runs from the northern to southern horizon. It is made of the combined light of billions of distant stars that lie in the plane of our home Milky Way Galaxy. In fact, Scorpius lies nearly in the direction of the center of our galaxy, so the Milky Way band is a little brighter there, especially if you see it in the dark countryside on a moonless night.
By 10 p.m. Scorpius will reside in the low west-southwest sky not all that far from the horizon. The brightest star in Scorpius is the bright brick-red star Antares at the heart of the beast. It’s the brightest star in that part of the heavens.
To the right of Antares you’ll see three dimmer stars in a vertical row that make up the Scorpion’s head. To the lower left of Antares look for the long curved tail of the beast. Antares has a definite reddish hue.
A star’s color tells a lot about its nature. Bluish white stars are the hottest; some have surface temperatures of more than 30,000 degrees. Reddish stars like Antares are cooler. In fact, Antares is cooler than our own sun, with a surface temperature of close to 6,000 degrees.
A thermometer plopped on the sun’s outer layer would show close to 10,000 degrees. The red hue of Antares is also reflected in its name. Antares is derived from the Greek language and means “rival of Mars” since it has the same ruddy tone as the planet Mars. You can easily confuse Mars and Antares with each other if you’re new to stargazing.
There’s no confusion between Mars and Antares when it comes to size. Mars is only about 4,000 miles across, a far celestial cry from the more than 600 million mile diameter of Antares.
The tail of Scorpius is worth looking for, because that’s where you can see what folklore refers to as the “Cat’s Eyes.” Two fairly bright stars, Shaula and Lesath, mark the stinger of the scorpion, but are also seen as the two piercing eyes of a great celestial cat.
With the naked eye these two stars aren’t really all that impressive, and not all that much better with a telescope. You are actually looking at a couple of really impressive stars, at least compared to the sun. Shaula, a little more than 700 light-years away is the brighter of the two cat’s eyes and is nearly 6 million miles wide, more than five times the diameter of our sun.
Shaula is also more than five times as hot as the sun with a surface temperature over 40,000 degrees, and it kicks out more than 35,000 times more light than our home star.
Lesath, the dimmer right eye of the cat, is almost as impressive as Shaula. It’s nearly 600 light-years away, and slightly smaller, cooler and dimmer, but still a mighty star in our galaxy.
Mike Lynch is an astronomer and professional broadcast meteorologist for WCCO Radio in Minneapolis and is author of the book, “Washington Starwatch,” available at bookstores. Check his website, www.lynchandthestars.com.
The Everett Astronomical Society: www.everettastro.org/.