One of my favorite constellations is Scorpius because it’s one of the few constellations that actually looks like what it’s supposed to portray. The only trouble with it is that in Washington state 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, in these 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 stretches across the eastern half of the sky this time of year. The Milky Way band 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 far away from heavy city lights on a moonless night.
By 10:30 p.m., when it’s finally dark enough for the stars to pop out, Scorpius is nearly at its high point in the sky, but it’s a low high point. The three moderately bright stars in a vertical row that depict the head of the scorpion are only about 30 degrees above the horizon, less than a third of the way from the southern horizon to the overhead zenith. The hook of the scorpion’s tail rides only about ten degrees above the horizon and unless you have a clear treeless view of the southern horizon you might not see it.
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. If you happen to get a chance to look for them tonight, the nearly full moon will act as a nice pointer. Just look about 12 degrees, or a little over one fist-width at arm’s length, to the lower right of the moon for Shaula and Lesath.
With the naked eye these two stars aren’t really all that impressive, and to be honest they’re not all that much better with a telescope. But as you have a stare-down with the Cat’s Eyes you are actually looking at a couple of really impressive stars, at least compared to the sun, our closest star, which is some 93 million miles away. Shaula, the brighter of the two cat’s eyes, is a star nearly 2 million miles wide, almost twice as big as the sun. Shaula is also twice as hot as the sun and puts out more than a thousand times more light than our home star. If Shaula were to take the place of the sun in our solar system, global warming would really get out of control. Fortunately, it’s a long ways from us, with astronomers estimating its distance at more than 275 light-years (one light year equals nearly six trillion miles). Since a light year is defined as the distance a beam of light travels in one year, the light we see from the bright left eye of the cat on these fine summer evenings left that star in the early 18th century, before the United States was even a country.
Lesath, the dimmer right eye of the cat, is even more impressive than Shaula as a star. The only reason it’s dimmer is that it’s much farther away, more than 1,500 light-years. Lesath is a behemoth star, more than 6 million miles in diameter and 15,000 times more luminous than our humble sun.
When you see the Cat’s Eyes of summer, there’s a lot more to those eyes than meets your eyes.
Mike Lynch is an amateur astronomer and professional broadcast meteorologist for WCCO Radio in Minneapolis and author of the new book “Washington Starwatch,” available at bookstores and on his Web site, www.lynchandthestars.com.