Tonight – December 22, 2017 – or any evening soon, look in the west shortly after sunset to find a famous asterism. An asterism isn’t a constellation. It’s a noticeable pattern of stars, in this case, the one known to us in the Northern Hemisphere as the Summer Triangle.
Good chance that you’ll be able to see these three brilliant stars.
Summer Triangle in northern winter? Sure. It’s called the summer triangle, because – for us in the Northern Hemisphere – summer is the season in which these stars are out from dusk until dawn.
The Triangle consists of three bright stars in three different constellations. They are Vega in the constellation Lyra the Harp, Deneb in the constellation Cygnus the Swan, and Altair in the constellation Aquila the Eagle.
Still, if you look for this pattern this month, you’ll find that, around the time of the winter solstice and the New Year, the Summer Triangle is descending in the west in early evening. It’s getting closer each evening to disappearing into the sunset glare.
How long into winter will you be able to see the Summer Triangle in your evening sky?
Deborah Byrd created the EarthSky radio series in 1991 and founded EarthSky.org in 1994. Today, she serves as Editor-in-Chief of this website. She has won a galaxy of awards from the broadcasting and science communities, including having an asteroid named 3505 Byrd in her honor. A science communicator and educator since 1976, Byrd believes in science as a force for good in the world and a vital tool for the 21st century. "Being an EarthSky editor is like hosting a big global party for cool nature-lovers," she says.