Enjoying EarthSky? Subscribe.

263,574 subscribers and counting ...

Summer Triangle and the galactic plane

Tonight, use the Summer Triangle and the constellation Cygnus the Swan to locate the sky’s galactic equator … and then project outward to the plane, or flat disk, of our Milky Way galaxy. Sure, it’s autumn here in the Northern Hemisphere, but the three brilliant stars that make up the Summer Triangle still shine. You’ll find them way up high in the October evening sky.

I suggest viewing the scene from the comfort of a reclining lawn chair, with your feet pointing southward.

As seen from mid-northern latitudes, the stars Deneb and Vega hang high overhead at nightfall and early evening. Vega, the brightest Summer Triangle star, shines to the west (or right) of Deneb, and Altair, the second brightest, is found roughly halfway between your southern horizon and straight overhead.

Donate: Your support means the world to us

The Summer Triangle and Milky Way. Image via NASA/ESA Altair shines a bit below center, while fainter Deneb is found at left center and the brightest star of the Summer Triangle, Vega, at upper left of center

As evening deepens, look for a modestly-bright star to pop out in between Altair and Vega. That’s Albireo, which depicts the Swan’s eye or beak. The line from Albireo to Deneb shows you the underside of the Swan’s body from head to tail. Three stars cross the body near Deneb to form what is known as the Northern Cross. Go one star farther out on each side of the Northern Cross to finish off the Swan’s wings.

Extend the Albireo to Deneb line in either direction to soar along the galactic equator (plane). Through binoculars, you’ll see that star clouds, star clusters and nebulae abound on this great galactic boulevard! Locate the Summer Triangle first, then the star Albireo, and you’ve got what it takes to find the glowing band of stars that we call the Milky Way.

Bottom line: You can use the Summer Triangle – and the constellation Cygnus the Swan – to locate the edgewise disk of our Milky Way galaxy.

Great Rift: Dark area in the Milky Way

Bruce McClure