We’ve just seen Orion’s return to the east before dawn, which means our northern summer is beginning to draw to the a close. But the Summer Triangle asterism still rules the skies. You can see it overhead at late evening. As seen from mid-northern latitudes, Vega – the Summer Triangle’s brightest star – shines high overhead around 11 p.m. local daylight saving time (10 p.m. local standard time). Altair resides to the lower left (southeast) of Vega, and Deneb lies to Vega’s left (east).
The Summer Triangle is not a constellation. It’s three bright stars in three different constellations, as the wonderful photo below – by Susan Jensen in Odessa, Washington – shows.
Here is the Summer Triangle asterism – three bright stars in three different constellations – as photographed by EarthSky Facebook friend Susan Jensen in Odessa, Washington. Thank you, Susan, for your excellent and beautiful work!
As the stars drift westward during the night Deneb will swing upward, to replace Vega as the overhead star some two hours later. Of course, the stars aren’t really moving. It’s the Earth’s rotation that causes the stars to move westward during the night, and the sun to go westward during the day.
The three stars of the Summer Triangle shine so wonderfully brilliantly that you can see them from light-polluted cities – or on a moonlit night. A bright waning gibbous moon will rise at early evening tonight, but these Summer Triangle stars will be able to withstand tonight’s drenching moonlight.
By the way, you can see the Summer Triangle in the Southern Hemisphere, too – although there do you call it the Winter Triangle? I wonder. South of the equator, people see an upside-down version of tonight’s sky scene, in contrast to our northern perspective. Late tonight, Southern Hemisphere residents will see Altair at the top of the Summer Triangle, and Vega and Altair sparkling at bottom.
Bottom line: The Summer Triangle asterism can be seen overhead at late evening now. The Summer Triangle is not a constellation. It’s three bright stars in three different constellations. These stars are Vega in the constellation Lyra the Harp, Deneb in the constellation Cygnus the Swan, and Altair in the constellation Aquila the Eagle.