Western Slope Skies
Tue October 9, 2012
The Summer Triangle
The Summer Triangle dominates the summer sky. It crosses the hazy band of the Milky Way, which is split into two by a large dust cloud near the star Deneb.
The points of the triangle are three of the brightest stars in the summer sky, and each is the brightest star in its own constellation. The brightest is Vega, in Lyra; second is Altair, in Aquila; and third is Deneb, in Cygnus. Even city-dwellers with glowing, light-polluted skies can find the Summer Triangle.
Using the Big Dipper as the guide, stretch your arm out at full length and measure about three hands-width from the two bowl stars closest to the handle. This will take you to a point in the middle of the Summer Triangle.
Vega is the brightest star in the triangle and is almost directly overhead in the summer. The name Vega comes from the Arabic word for “swooping eagle” or “vulture.”
Once you have found Vega, look south-southeast and you will see Altair in the constellation Aquila (the Eagle). Altair spins at an amazing 470,000 miles per hour. This rotation has stretched Altair into an egg shape, wider than it is tall. Altair is one of our nearest neighbors, 16 light-years away.
The most prominent constellation that forms part of the Summer Triangle is Cygnus. The main stars in Cygnus create a pattern in the sky known as the Northern Cross, with Deneb at the top.
Cygnus is in an area of the Milky Way that contains many objects easily seen with an amateur telescope, including a beautiful gold and blue double-star at the base of the cross, Albireo.
Western Slope Skies is produced by members of the Black Canyon Astronomical Society.