Learning about the Summer Sky

When out shooting the Moon or Milky Way, make sure you take a little time to look around and see the rest of the night sky. Most people have heard of at least a few of the constellations. One popular in the north is the Summer Triangle Constellation. Well, it’s not technically as a constellation for reasons we will see.

Most people know the names of the constellations of the ecliptic that lie along the path the sun travels throughout the year – Virgo, Leo, Sagittarius, or even Ophiuchus to name a few. These are the constellations of the Zodiac. (Ask anyone if they have the star sign Ophiuchus and see how puzzled they are.)

In the northern hemisphere, the Big and Little Dipper come to mind, and perhaps even the great Greek heroes like Perseus or Hercules. In the southern hemisphere, the Southern Cross should be a familiar name.

All constellations are what is called an “Asterism.” An asterism is a group of stars that create a pattern, a kind of connect-the-dots stick-figure pattern. These patterns helped early humans learn and remember places in the night sky. The process of making these patterns was utterly arbitrary and different cultures created unique asterisms.

While the constellations are the most commonly known names of these patterns, the summer sky in the northern hemisphere has one asterism that is super easy to pick out and makes a great way to get started learning the night sky. It’s called the Summer Triangle.

Vega, Deneb, Altair = Three Stars

The Summer Triangle is made up of three stars, Altair, Deneb, and Vega, each located at the vertex of an imaginary triangle, hence the name. These stars are typically the brightest stars overhead during northern hemisphere summer evenings. Since the Summer Triangle is bright enough to be seen in all but the worst light-polluted conditions, it makes a great way to orientate yourself to the night sky. The triangle is nearly a right triangle with Vega located at the corner of the right angle.

Deneb is the brightest star in the constellation Cygnus, the Swan. Cygnus is nearly lined up with the dark lanes of the Milky Way to the northwest of the Milky Way Core. Deneb is the head of the Cygnus, with its body nearly aligned with the dark lanes. Deneb is almost 196,000 times brighter than the sun, and it is perhaps the most inherently luminous star visible from Earth.

The Summer Triangle connects the stars Deneb, Vega, and Altair. 
Star Field courtesy of stellarium.org Graphics Copyright 2018 Kirk D. Keyes
The Summer Triangle connects the stars Deneb, Vega, and Altair.
Star Field courtesy of stellarium.org

Vega is to the east and a little south of Deneb, in the constellation Lyra, the Lyre. It’s the 5th brightest star in the night sky and second in the northern hemisphere.  

Altair is in the constellation Aquila, the Eagle. It is just a little west of the dark lanes of the Milky Way. Altair is one of the closest visible stars to Earth at slightly under 17 light years away.

Locating the Milky Way

A line drawn between Deneb and Altair makes a great way to locate the Milky Way. The Summer Triangle can be seen even in the spring during the early morning hours. And in fall, it’s moved into the western sky during evening hours. It is visible in much of the southern hemisphere, where it lies low to the horizon during the Winter months.