The 'Goat Star' is back: How to see Capella in the night sky this month

It's funny how you remember certain events in your life. Recently, my mind wandered back to mid-August of 1975, when I and several friends went camping near the little community of Thurmond, New York in the southern Adirondack Mountains. We had headed there to get far away from the light-polluted environment of the New York City area in order to enjoy some dark, starry night skies. 

Each of us had brought binoculars, telescopes and cameras, and as we set them up in front of our tent near sundown, we caught the attention of some nearby campers, who told us about a "mysterious UFO" that appeared to them each night. From the descriptions that they gave, it appeared late each evening, hovering just above the horizon in a general northerly direction. It wasn't there at dusk, but would appear prominently just a few hours later. 

One young boy, around 10 years old, gave a rather vivid description: "It's very bright and flashes different colors ... one moment it's bright yellow, then orange and red — sometimes even blue!" My friends and I were in a quandary as to what our fellow campers were seeing. Certainly, in the direction that they were pointing, and at the hour they were seeing this object, it seemed that there couldn't have been any bright star or planet lurking. 

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Still, they were insistent, so I told them that if they saw it late that night, to come over and tell us. Later that evening (it was not quite 11 p.m.), as I was looking through my telescope at the famous globular star cluster in the Hercules constellation, I heard the footsteps of our neighboring campers, led by the 10-year-old boy who excitedly said, "It's back! We just saw it! Come and take a look!"

I was led to a spot where the local tree line was low, providing a virtually unobstructed view, and there, scintillating low above the north-northeast horizon was the "infamous UFO." 

Except it wasn't an unidentified flying object at all. In fact, it was an old friend of mine from the winter, making an out-of-season midsummer appearance: It was Capella, the brightest star of the constellation of Auriga, the charioteer.

Like a celestial train 

The legendary astronomy author and stellar cartographer George Lovi (1939-1993) loved skywatching, but was also an avid enthusiast of trains and railroads. To Lovi, the first appearance of the annual winter pageant of bright stars and constellations was akin to a railroad train. Like an approaching locomotive with its bright lone headlight appearing low on the horizon, Capella would appear to lead the bright winter retinue of stars, which, like a railroad train would pass before us. 

Soon, in the hours that followed we would see the familiar constellations of Taurus the bull, Orion the hunter and his two faithful canine companions, Canis Major and Canis Minor. And finally, Gemini, the twins with its two bright stars, Pollux and Castor. Lovi would often point to those two stars and say that they marked the taillights on the caboose of our imaginary celestial train; those would be the last of the winter twinklers to bid us a farewell low in the northwest evening sky by late spring.

But it was Capella that always led off the procession.

In fact, it's the sixth-brightest star in the sky (magnitude 0.08) and as seen from mid-northern latitudes, ranks number four behind Sirius, Arcturus and Vega. To make a positive identification, just go to the Big Dipper and mentally extend a line from the top two stars in the bowl, off to the right and go straight on from there and you'll hit Capella. 

A baffling blend of myths

Auriga is one of those star patterns whose exact origin is a hopeless mix of antique conceptions. The Greek and Roman legends made Auriga a famed trainer of horses and the inventor of the four-horse chariot. But the most ancient legends also had Auriga as a goatherd and a patron of shepherds. 

The brilliant golden-yellow Capella was known as the "Goat Star," with a nearby triangle of fainter stars representing her kids. The confusion in concepts is reflected in the ancient allegorical pictures and star names. Auriga is usually represented holding a whip in one hand in deference to the charioteer story, but in his other arm he is holding a she-goat (Capella) and her three kids. 

Well ... whatever floats your goat.

In his classic guidebook, "The Stars, A New Way to See Them" (Houghton Mifflin, 1976), Hans A. Rey (1898-1977) drew Auriga looking like a man with a tough expression, with a jutting chin and a pug nose, "as befits the driver of a war cart."

More than meets the eye

Capella is located almost 43 light-years away. And it is, in reality, part of a multiple star system, containing at least four components. Capella A and B are quite similar to each other; two stars roughly 10 ten times larger than our own sun, and about 72 times more luminous than our home star. Both are about 2.5 times more massive than the sun and whirl around each other every 104 days, separated by only about 69 million miles (111 million km). They are much too close to be seen individually through a telescope; their duplicity was first detected with a spectroscope at California's Lick Observatory in 1899. 

In 1935, a much fainter pair of much cooler, red dwarf stars were discovered about 100 billion miles (160 billion km) from the main pair. If we were to design a scale model of the Capella binary system, we would have two globes each roughly 10 inches (25 centimeters) in diameter and spaced about 10 feet (3 meters) apart representing A and B, while the much fainter pair would each measure less than an inch in diameter and spaced 420 feet (128 m) apart and 21 miles (34 km) from the main pair A and B! 

Catch it on the rise

As was noticed by my fellow campers from all those too many years ago, Capella appears to rise well to the north of due east. In fact, it is the nearest to the North Pole of the sky of all the first-magnitude stars, and across much of the 48 contiguous United States it is visible at some hour of the night throughout the year. From New York City, for example, Capella is below the horizon for only 3 hours and 15 minutes out of a 24-hour day. 

Lying 46 degrees north of the celestial equator, Capella can pass directly overhead for anyone living at that latitude north of the terrestrial equator (say, Houlton, Maine or Geneva, Switzerland). And for anyone living at points north of 44 degrees latitude (for example, Minneapolis, Minnesota or Bologna, Italy), Capella will appear to graze the northern horizon, but will not go below it. From my campsite in the southern Adirondacks (latitude 43.7 degrees north), Capella skims out of sight just below the northern horizon for just 35 minutes a day. 

This week, for those at 40 degrees north latitude (Philadelphia; Columbus, Ohio), Capella will rise at around 9 p.m. At latitude 30 degrees north (New Orleans; St. Augustine, Florida), closer to 10:35 p.m. local time.

Lastly, you may remember my young friend excitedly describing Capella as appearing to flash different colors. When it's rising (or setting) this is not surprising. While high in the sky, this star appears to glow golden yellow, when the air is unsteady, or especially when it is low to the horizon it seems to flicker and splinter with all the colors of the rainbow. Check it out for yourself this week. 

Bottom line: Capella is back for the beginning of another season leading us into fall and ultimately winter. 

Here we "goat" again.

Joe Rao serves as an instructor and guest lecturer at New York's Hayden Planetarium. He writes about astronomy for Natural History magazine, the Farmers' Almanac and other publications. Follow us on Twitter @Spacedotcom and on Facebook.