Some people see a paper boat, others a goat, some a sloppy triangle and others the mischievous grin of the Cheshire Cat. Whatever we behold in the curious constellation of Capricornus, I was just happy for clear skies to see it last night. Two weeks of cloudy nights have been too much for this star-craved human to bear.
With the return of the stars, I noticed that Mars has been on the move east and now shines from the center of Capricornus. The Red Planet hasn’t lost its visual magnetism despite having faded to magnitude –1.0 in part because it has no competition — Capricornus is one of the fainter constellations with no star brighter than third magnitude. Mars still bests Canopus, the second brightest star, and stands only half a magnitude behind the brightest star Sirius.
Mars won’t be locked inside its Capricornus cage for very long. Each passing night it edges eastward (to the left from the northern hemisphere) and further north as it orbits the sun. If you watch closely and compare the planet’s night-by-night position with stars in the figure, you can actually see Mars move in 24 hours. Don’t wait too long — by Halloween, the planet will have fled
But first you have to find Capricornus, and it’s not a bright constellation. Good thing Mars is there. Starting at the planet, look a little more than one outstretched fist to the upper right to find a pair of 3rd magnitude stars, Alpha and Beta Capricorni. Now, return to Mars and look a little more than a fist to the upper left to spot Delta Cap (short for Capricorni). Delta is the brightest star in the constellation by a hair. Second brightest is Beta and third brightest, Alpha.
Usually, a constellation’s brightest star is Alpha, followed by Beta then Gamma and so on. Usually. But sometimes a star’s position in the sky is more important than splitting hairs about its brightness. To the ancients, stars had other important qualities besides just brightness. Position mattered, too.
That’s the case with Alpha Cap, which got the designation because it’s the brightest, westernmost star in the figure. While it sets before the others, it also is the first to rise, lending it notoriety.
Beta really is Capricornus’ second brightest star, and having it right next to Alpha makes for a convenient, easy-to-remember Alpha-Beta pairing.
Astronomer James Kaler once wrote: “Omega stars,” those named with the last letter of the Greek alphabet, get little respect.” That may be true but Capricornus’ Omega takes a prominent position in the constellation because it marks the bottom apex of a triangle formed by Delta and the Alpha-Beta duo. If you can find the basic triangular outline, with or without the fainter “filler” stars, congratulations!
Capricornus is one of the most ancient constellations and represents a unique figure among the 88 groups, a creature that’s half goat and half fish. The myth comes to us from Mesopotamia from 5,000 years ago. Then, the figure represented the boat of the god Enki, the Sumerian god of water, wisdom and creation. Enki means “Lord of the Earth” and his symbols were the fish and the goat, both representations of fertility and identified with the constellation to this day.
Because all stars except the sun are so far away, their light takes from several to tens of thousands of years to reach our eyes. To look at a star is to look back in time. Capricornus telescopes time, taking us back across dozens of centuries to reconnect with one of the great cultures of the ancient world.