Summer Night Sky (Northern Hemisphere)

By 9 p.m. on August 15, the stars have moved westward by 90 degrees since mid-month in May.  Leo, which was just past overhead in the spring sky, has now set in the west.  The Big and Little Dippers have also made a quarter turn around Polaris relative to their position at the same time on May 15.  In between the Big Dipper and Little Dipper lies the long, winding, and dim constellation Draco, the Dragon.

The sky at 9 p.m. on August 15 from 40oN latitude

The sky at 9 p.m. on August 15 from 40 degrees N latitude.  Click to open in a new window.

But new constellations have risen in the east, bringing into to view the bright stars of the summer sky.  High overhead you will see the dazzling blue-white star Vega in the small constellation Lyra, the Lyre.  The constellation looks like a little parallelogram formed by four blue-white stars that are fainter than Vega.  This star group is about as large as three fingers held side-by-side at arm’s length.

The larger constellation Cygnus and its bright star Deneb lie northeast of Vega.  Cygnus is supposed to represent a flying swan, but its most easily recognized as its informal name, the Northern Cross”.  Further to the southeast you will see the bright star Altair in the eye of the constellation Aquila, the eagle.  The stars Vega, Deneb, and Altair form what’s known as the “Summer Triangle”.  You can follow the triangle on its slow path westward each night well into late autumn.   Next to Vega, almost directly overhead, you’ll see a “keystone”-shaped group of four stars which marks the body of the constellation Hercules.  The Keystone is a little larger on each edge than the parallelogram of Lyra is long.

Look also for the tiny constellations Delphinus and Sagitta.  They look very much like the dolphin and arrow after which they are named.

Summer_Triangle_BW

The “Summer Triangle” lies nearly overhead in late summer evenings as seen from the mid-northern hemisphere

Perhaps the finest celestial sights of the northern-summer sky lie above the southern horizon.  That’s where you’ll find the long band of star clouds of the Milky Way in the constellations Scorpius and Sagittarius.  Scorpius represents a celestial scorpion, and it does so convincingly, with its claws pointing northward and its curved stinger dipping southward.  Antares is the very bright red star at the heart of the Scorpion in the south-southwest.   The Milky Way grows thickest in the southeast in the teapot-shaped constellation Sagittarius.  This constellation is thick with star clusters and nebulae where new stars are forming.  If you have dark sky, you will see some of these clusters and nebula with your unaided eye as faint misty patches of silver-white.  These are dazzling sights in binoculars or a small telescope. 

Towards Sagittarius lies the center of our galaxy, which is why the star clouds of the Milky Way appear so thick in this part of the sky.  These star clouds are very difficult to see from urban areas where bright city lights wash them out, but they are very obvious in clear sky far away from city lights.