The first day of summer is June 21, just about two weeks away. The Summer Triangle now appears in the east at dusk. Made of three bright stars from three different constellations, the Summer Triangle can be picked out when the brightest stars are appearing after sunset, so it can be an easy target for young astronomers just starting to learn their stars in the summer months.
The Summer Triangle is not a constellation itself, but an asterism. An asterism is a pattern of stars that may be part of an official constellation or made up of stars from several constellations. A constellation (by today’s astronomical consideration) is an internationally defined area of the night sky. The stars which make up the Summer Triangle are:
- Vega, of Lyra the Harp. Vega is the topmost and brightest star of the triangle.
- Deneb, of Cygnus the Swan. Deneb is lower left of Vega, by a visual distance of two or three fist-widths at arm’s length.
- Altair, of Aquila the Eagle. Altair is farther to the right, and the last of the three stars to rise.
Under a clear, dark sky you can see the Milky Way stretching through and beyond this large starry triangle. Aim some binoculars at this region to marvel at the sheer quantity of stars found here.
The Summer Triangle will be visible now all summer. As we approach autumn, it will reach a position high in the south to overhead at dusk and early evening, so there is plenty of time for your little astronomers to become acquainted with this asterism.