See the Summer Triangle in northern autumn
The Summer Triangle and its 3 stars
The Summer Triangle is the signature star formation in the Northern Hemisphere’s summer sky. However, as the September equinox comes and goes – and as the weeks of autumn begin to slide by – you’ll still notice this famous trio of stars. So, look for the Summer Triangle after dark in early November. It will actually continue to shine after dark in November and December, and is even visible still in January. Look for it tonight in the early evening, high in your western sky.
By the way, the Summer Triangle isn’t a constellation. It’s an asterism, or an obvious pattern or group of stars with a popular name. In fact, the Summer Triangle consists of three bright stars in three separate constellations. The bright star Vega is in Lyra the Harp. Deneb is in Cygnus the Swan. And Altair is in Aquila the Eagle.
In the month of June – around the June solstice – the Summer Triangle pops out in the east as darkness falls and shines all night long. But now – after sunset in November – the Summer Triangle appears high in the western evening sky. As evening deepens, the Summer Triangle descends westward, with all three of its stars staying above the horizon until mid-to-late evening.
Altair – the Summer Triangle’s southernmost star – will set around 10 to 11 p.m. tonight at mid-northern latitudes. Notice where you see the Summer Triangle at a given time this evening. The Summer Triangle will return to this same place in the sky some four minutes earlier with each passing day, or two hours earlier with each passing month.
Look for Orion, too
Then as the Summer Triangle sinks close to the western horizon around mid-evening, turn around to see Orion the Hunter – the signpost constellation of winter – rising in the east.
Bottom line: Look westward this evening for the three brilliant stars of the humongous Summer Triangle: Vega, Deneb and Altair. In fact, you can still see the Summer Triangle through January.