Jimmy Westlake: A river of stars
February 3, 2008
The very familiar star pattern of Orion the Hunter is found nearly overhead at 8 p.m. as January ends and February begins. The bright stars Betelgeuse, at Orion’s shoulder, and Rigel, at his foot, join the three stars marking Orion’s Belt to form one of the most widely recognized star patterns in the entire sky. Today, I would like to draw your attention to a little star just above the bright star Rigel. Although it lies very close to Rigel in the sky, this star does not belong to the constellation Orion, but falls in the neighboring constellation of Eridanus, the River. The little star is named Cursa, meaning, the “foot stool,” because Orion seems to be stepping on it with his big foot, Rigel.
In fact, the star Cursa is the first bright star in a long, meandering stream of stars that represents the Po River in Italy. The river was immortalized in the stars to console Helios, the mythological sun god of the Greeks, after his son Phaethon drove his fiery chariot too close to the Earth and caught it on fire. Zeus, the king of the Greek gods, had to shoot down the runaway lad and his chariot with a lightening bolt to spare the Earth. Phaethon’s body fell like a meteor into the Po River, where his sisters wept tears that turned into drops of amber.
To locate the celestial river, Eridanus, looate the star Cursa near Orion’s foot and connect the dots toward the right, or west, to trace out an enormous backward letter “S.” The “S” shape is every bit as large as Orion but is composed of fainter stars. Eridanus then flows straight down below the southern horizon and out of view. Overall, Eridanus the River is the sixth largest constellation in our sky.
Folks living below latitude 32 degrees N get to see the bright star Achernar that marks the pool at the end of the river. That’s roughly the latitude of Midland, Texas, and Savannah, Ga. The entire state of Colorado is too far north to get a glimpse of Achernar, the sky’s tenth brightest star.
The unassuming star Epsilon Eridani is an important star for a couple of reasons. After Sirius, the Dog Star, Epsilon Eridani is the second-closest star to our solar system visible with the unaided eye from Colorado. It has often been used in science fiction stories because it is a slightly cooler version of the sun and is known to possess at least two planets of its own. Planets orbiting Epsilon Eridani probably would not bear intelligent life forms, in spite of what science fiction authors might think, because the system is relatively young, only half a billion years old, compared to 4.6-billion years old for Earth.
Professor Jimmy Westlake teaches astronomy and physics at Colorado Mountain College’s Alpine Campus. He is an avid astronomer whose photographs and articles have been published on the Web sites of CNN.com, NASA’s “Astronomy Picture of the Day” Web site, Spaceweather.com, Space.com, Discover.com, MSNBC.com, NationalGeographic.com, and in Sky & Telescope, Astronomy, Night Sky, Discover and WeatherWise magazines. His “Celestial News” article appears weekly in the Steamboat Pilot & Today newspaper. His “Cosmic Moment” radio spots can be heard on local radio station KFMU.