Sky ArchiveTonight

Vega and its constellation Lyra

A chart showing the Summer Triangle asterism, with the 3 small constellations Sagitta, Vulpecula and Delphinus.
The Summer Triangle isn’t a constellation but a large asterism consisting of 3 bright stars in 3 separate constellations. These stars are Vega, Deneb and Altair.

Tonight, look eastward during the evening hours, and it’s hard to miss the season’s signature star formation, the asterism called the Summer Triangle. Its stars – Vega, Deneb and Altair – are the first three to light up the eastern half of the sky after sunset, and their bright and sparkling radiance is even visible from light-polluted cities or on a moonlit night.

Try looking first for the most prominent star in the eastern sky, which is Vega in the constellation Lyra the Harp. Vega is blue-white in color. It’s sometimes called the Harp Star. It’s about 25 light-years away. Many people recognize its constellation, Lyra, as a triangle of stars connected to a parallelogram.

Star chart of constellation with prominent stars labeled, also location of M57 the ring nebula.
The constellation Lyra the Harp.

It’s hard to gauge the humongous size of the Summer Triangle by looking at our little chart. A 12-inch (1/3 meter) ruler, when placed at an arm’s length from your eye, spans the approximate distance from Vega to the star Altair. And an outstretched hand more or less fills the gap between Vega and Deneb.

More than any other month, July is the month of the Summer Triangle. At mid-northern latitudes, the Summer Triangle’s stars – as if a trio of school kids on vacation – stay out from dusk till dawn, dancing amid the stars of our Milky Way galaxy. As our Earth turns tonight, Vega, Deneb and Altair travel westward across the sky. The Summer Triangle shines high overhead in the middle of the night, and sparkles in the west as the rose-colored dawn begins to color the sky.

Star field with 3 labeled constellations, 4 labeled stars, the location of M57, and outline of large triangle.
The Summer Triangle, photographed by Susan Jensen in Odessa, Washington.

Our Summer Triangle series also includes:

Part 2: Deneb and its constellation Cygnus

Part 3: Altair and its constellation Aquila

Bottom line: The Summer Triangle consists of 3 bright stars in 3 different constellations. The brightest is Vega in the constellation Lyra.

EarthSky astronomy kits are perfect for beginners. Order yours today.

July 2, 2020
Sky Archive

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Deborah Byrd

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