See Draco the Dragon in the Night Sky This Week

The constellation Draco is particularly bright this week.
The constellation Draco is particularly bright this week.
(Image: © Starry Night software)

Draco the Dragon is well worth spotting this week, as it is particularly bright in the northern sky, winding around the Little Dipper.

The Chaldeans, Greeks and Romans all envisioned a dragon here, while Hindu mythology claims the creature is an alligator and the Persians saw a man-eating serpent.

Draco has been identified with a number of ancient Greek stories: A dragon guarded the entrance to the Hesperides, where the golden apples grew; Hercules killed it. 

Related: The Brightest Visible Planets in June's Night Sky: How to See Them (and When) 

Another tale identifies the dragon as fighting on the side of the Titans, essentially a creature of darkness and primordial chaos, and companion of the ancient and formidable gods of nature. When she was fighting the Titans, Athena, the goddess of wisdom and war, fully arrayed in armor and carrying her magic shield, threw a dragon up into the sky after it attacked her. With all her strength, she swung the beast in a wide circle and he spun around and around, his body ultimately becoming curved and twisted until he struck the very top of the sky around which the stars revolved. And there he lies to this very day.

Much of the dragon is a line of stars winding at first to the east, then back westward, snaking between the Big and Little dippers. It's not as absurdly long as Hydra, the Water Snake, but in a way, since it is up near the Pole, it wraps even farther around the sky: a third of the way around, from the Pointer Stars in the Big Dipper, as far as the stars Vega and Deneb.  

Dragon's head, a lozenge or camels? 

Also like Hydra, the most conspicuous part of Draco is his head. Much of the Dragon's body is hard to pick out, but his head is a distinctive, naked-eye asterism of four stars (some call it the "Lozenge"), that is interesting to examine with binoculars. Arabic nomadic tribes, however, did not see a dragon's head, but rather referred to these stars as "The Protecting Mother Camels." 

This week, you'll find these four stars high in the northern sky, almost directly overhead during the late evening hours, around 10 or 11 p.m. local daylight time.

Draco seems to be eyeing the brilliant blue-white star Vega, located about 15 degrees away. Recall that your clenched fist is equal to roughly 10 degrees when held at arm's length; Vega is placed roughly one and a half fists from Draco's head.

Draco's nose is marked by the bright second-magnitude star Eltanin, a name that may be derived from At-Tinnin, which means "the head of the great serpent" in Arabic. The 15th century Uzbek astronomer Ulugh Beg referred to it as Al Ras al Tinnin, "the head of the dragon." Interestingly, the earliest Sumerians considered these stars to represent the dragon Tiamat, yet another name from which Eltanin may have been derived.

Once you have Eltanin in view, try defocusing your binoculars ever-so-slightly to better see the subtle orange tint of this star. Astronomers estimate that it is about 154 light-years away, and it's a true giant, 48 times wider than our sun, 72% more massive, and 471 times more luminous.

Contrast Eltanin's color to that of Rastaban, the second brightest of the four stars. Rastaban is a very delicate, pale yellow-white, third-magnitude star about 380 light-years away from Earth. Like Eltanin, its name also is a loose transliteration of "dragon's head."

The trapezoid's northeast corner is marked by 4th magnitude Grumium, "the dragon's lower jaw." Similar to Eltanin, Grumium is a giant star, though its slightly lighter orange hue may prove elusive because of the star's dimness. 

During World War II, the military named two ships for these stars, the cargo ship U.S.S. Etamin and the aviation supply ship U.S.S. Grumium. 

The "real twins" 

Last, but certainly not least, is the faintest, but I think the most interesting of the four stars: Nu Draconis. This is a lovely double star, suitable for binocular viewing. Nu1 and Nu2 are twin white jewels that are separated by 1/30 the apparent size of the moon.

The legendary British astronomer Sir Patrick Moore noted that you could split this star with the naked eye; however, you must have extremely acute eyesight to do so. But the stars are easy to resolve with binoculars. I accidentally stumbled across Nu Draconis when I was a teenager growing up in the Bronx and just cutting my eye teeth on the night sky.

The pair look like distant headlights. With all due respect to the much brighter and most famous "Twin" stars, Pollux and Castor in Gemini, Nu1 and Nu2 are true stellar twins. Where the Gemini stars differ in brightness by a half magnitude, the Nu stars shine at +4.8 magnitude. They are about 120 light-years away; calculating the celestial geometry tells us the two stars are separated by 60 times the distance from the sun to Pluto. 

Check them out this week.

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, and he is also an on-camera meteorologist for Verizon FiOS1 News in New York's lower Hudson Valley. Follow us on Twitter @Spacedotcom and on Facebook

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