Your Guide to the Summer Night Sky

by AMNH on

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Astronomer Charles Liu has simple advice for summer stargazers: start big!

“I always tell people to look for the Summer Triangle,” says Dr. Liu, a resident research associate in the Museum’s Department of Astrophysics. “Three bright stars that make an isosceles triangle covering half the night sky. Each marks a major constellation.”

Three bright stars stand out against a dark night sky filled with stars.
The asterism of the "Summer Triangle" is a giant triangle in the sky composed of the three bright stars Vega (top left), Altair (lower middle) and Deneb (far left).
A. Fujii/ESA/Hubble

Vega, the most visible of the three, is in the constellation Lyra, or the lyre; the star Altair is in Aquila, the eagle; and Deneb is part of Cygnus, the swan. This last constellation also has another big visual clue within it: the so-called Northern Cross, formed by the body and shoulders of the swan.

Many stars of various levels of brightness fill a dark night sky.
The constellation of Cygnus appears in the top of the image.
A. Fujii/ESA/Hubble

Such clear points of orientation are especially important for astronomers in the New York City area, where the night sky is “so highly polluted by artificial light,” says Dr. Liu, who is also an astrophysics professor at the City University of New York’s College of Staten Island.

Once you’ve located these, use a star chart to find other stars and constellations in relation to these celestial landmarks as the night progresses.

“They will move over the course of the night,” explains Liu. “Just like the Sun, they rise in the east and set in the west, but their relative position to one another doesn’t change. At 9 pm, they will be in the same location relative to each other as at midnight.”

In summer, expect to find such familiar figures of the zodiac as Taurus, Gemini, and Leo the Lion, whose mane and front paw resemble a backward question mark with a very bright star—Regulus—at the bottom. The Big Dipper and the Little Dipper, with its North Star, will be visible, each forming the tails, respectively, of the two bears, Ursa Major and Ursa Minor.

Stars in the night sky, the brightest of which from the Big Dipper shape; text reads Draco, Canes Venatici and Ursa Major, as well as star names.
A wide-field view of the constellation of Ursa Major, the asterism known as the "Big Dipper.
NASA, ESA, Z. Levay (STScI) and A. Fujii/ESA/Hubble

One useful trick, says Liu, is to start early, near sunset, when the Summer Triangle and Northern Cross will not be lost among the many stars that are visible in the later, darker sky. The phases of the Moon must be factored in, too, because bright moonlight will wash out some stars. This summer, the Moon was full on July 9 and will be full again on August 7—so take a stargazing pass that evening.

Moonlight can obscure meteor showers too, although two of the best—the Delta Aquarids on July 28 and 29 and the Perseids on August 12 and 13—should still be visible at their peaks. Best viewing for meteor showers? A dark location after midnight. 

Of course, the biggest celestial event this summer will be the total solar eclipse on August 21, which will hit a swath of North America, from Oregon to South Carolina.

But scanning the skies on any given summer night offers ample reward. Says Liu, “It gives you a sense of where you are in the universe.”

A version of this story originally appeared in the Summer 2017 issue of Rotunda, the Member magazine.