Star Vega Shines Bright Overhead on July Nights

Jul 25, 2017
Star Vega
NASA JPL

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Away from city lights in mid-July, one could see as many as 2,500 naked eye stars. But only one star stands out because it’s the only bright star directly overhead—and that’s Vega. This brilliant blue-white star is a favorite of stargazers and astronomers.

For those living at a latitude between 39 and 44 degrees, meaning the region encompassing Denver, Philadelphia, New York city, Boston, Salt Lake City, Topeka, and Springfield, Vega is the only bright summer star that ascends to within a few degrees of the exact zenith in July.

Vega, the Vegetarian Star?

Boasting the shortest stellar name, it’s nonetheless routinely misspoken as VAY-ga. It’s actually pronounced VEE-guh. Its name derives from an old Arabic word pronounced WEE-guh, whose meaning was a falling eagle or vulture. Indeed, in my antique astronomy books from the 18th century, the star is listed as Wega.

Vega is the 5th brightest star visible from Earth, and the 3rd brightest easily visible from mid-northern latitudes, after Sirius and Arcturus. Vega is also one of three stars in the famous star pattern called the Summer Triangle, along with Deneb and Altair. 

Vega Folklore

Interestingly, there’s a story about Vega and Altair. In Asian folklore, a celestial goddess falls in love with a mere mortal. The goddess’ father forbids their union and it is doomed. However, the gods take pity and place the two lovers in the sky as Vega and Altair.  Separated by a celestial river, the Milky Way, these star-crossed lovers are only allowed to reunite once year. They cross a bridge of magpies across the Milky Way on the 7th night of the 7th Moon.

Vega is also called the Harp Star since in the constellation of Lyra, the Harp. According to Greek myth, the musician Orpheus played the harp to entrance both god and moral.

vega-folklore.jpg

Vega: The Reference Star

Shining at a steady magnitude zero, Vega serves as the “standard candle” used by the worldwide astronomical community to calibrate the brightness of everything else in the universe. Like the French bar of platinum that defined the meter until recently, Vega is the sky’s reference point for the magnitude system. It’s an ideal choice because it displays not the slightest flickering or unsteady habit; it’s also a single star like our Sun instead of a binary like most. Its brilliance, equal to 58 suns, emanates from a dazzling 2.7 million-mile ball with a surface of nearly pure hydrogen, floating at the relatively nearby perch of 25 lightyears.

Why is it blueish in color? Vega’s surface temperature is nearly 17,000 degrees F, making it about 7,000 degrees hotter than our Sun.

Vega: A Sort of North Star?

But it’s still not quite a monument to normality. In 1994 a team of Canadian astronomers announced that Vega has unsuspected peculiarities. It spins much faster than anyone imagined, in a giddy 11 hours compared to 25 days for our own Sun. And its pole of rotation is pointed straight toward us, give or take five degrees. For any Vegans looking skyward, our Sun is its north star!

Twelve thousand years from now, we’ll return the favor. Vega periodically becomes our own pole star as Earth’s axis wobbles through its 26-millennium precession. Brightest of all north stars through the aeons, it nonetheless misses the celestial pole by four degrees, making it nearly ten times less precise than the current one, Polaris.

People who eschew all animal foods call themselves Vegans, a term probably coined in the 1940s. But their ancestors did not likely hail from Vega. Despite being encircled by a dusty disk whose infrared signature has been interpreted as evidence of a planetary system, actual life is implausible there because of the star’s youth.

As if this weren’t enough to keep us interested, Vega marks the approximate direction toward which we travel in space. As our entire starry neighborhood participates in the galaxy’s grand rotation, we do a little nine mile-per-second sideslip in Vega’s direction. Those who mistakenly think that the whole universe races away from us might take a glance overhead. In a cosmos where the redshift is as common as pizza, this diamond at the zenith displays the much rarer blueshift.

So enjoy Vega right now as it hovers overhead near the zenith. But no need to rush. Vega will only grow brighter as it heads our way, keeping our descendants company through the aeons.

About This Blog

Welcome to “This Week’s Amazing Sky,” the Almanac’s blog on stargazing and astronomy. Wondering which bright objects you’re seeing in the night sky? Want to learn about a breathtaking sight coming up? Bob Berman, longtime and famous astronomer for The Old Farmer’s Almanac, will help bring alive the wonders of our universe. From the beautiful stars and planets to magical auroras and eclipses, we’ll cover everything under the Sun (and Moon)!

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Any know if that print is for sale. Love it. Great article as well.

Article on Vega

Fascinating article!
Informative, and, fun!!

DorothyC

Fun Column!

Another excellent article Bob. Both informative and fun! Great to share with family and friends. I love ancient folklore Bob shares. Thank you!

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