Midnight. Too late for a look at the sky? Not if you hungry for a token of summer. It’s out there alright – the Summer Triangle. It’s unclear who named this giant triangle formed by three of summer’s brightest stars – Vega, Deneb and Altair – but its usage has been around since at least the 1920s. The first person we know of to connect the three stars in a triangle, even though he didn’t give the figure a name, was the German astronomer Johann Bode back in 1816. Bode created some of the most beautiful star atlases ever made.
Sometime in the late 1920s Austrian astronomer and prolific astronomy popularizer Oswald Thomas described these stars as the “Grosses Dreieck” (Great Triangle) and later in 1934 as the “Sommerliches Dreieck” (Summerly Triangle). Another great name in astronomy, England’s Patrick Moore, who passed away last December, described the trio as the Summer Triangle starting in the 1950s in his many books and lectures.
Tonight you’ll see the famed asterism crest the eastern horizon around midnight. Vega, the westernmost of the three and earliest to rise, sparkles in the northeast by 10 p.m. Deneb’s up by 11 and joined by Altair shortly before midnight. Although tipped on its side and slung low in the east in early May, by month’s end, the triangle stands higher and becomes visible at nightfall.
From July through September the Summer Triangle rules the sky, standing upright in the south balanced on its southermost apex Altair. That’s how it got its name of course, since it’s most obvious in the mid to late summer months. Come October and November, the figure scootches over to the west and by December it’s gone – just in time for winter.
The brightest of the three pivotal stars is Vega in the constellation Lyra the Harp. All Lyra’s stars are dim, but Vega more than compensates with a radiance as pure and white as burning magnesium.
To find Deneb, the brightest star in Cygnus the Swan or Northern Cross, reach your balled fist to the sky and look ‘two fists’ to the lower left of Vega. Altair in Aquila the Eagle is way down to the lower right. Three-plus fists will get you there. Vega, Deneb and Altair are all easy to see even from a middle-sized city and suburban areas.
An additional treat awaits the eyes of rural observers or those who make a drive to the country. The Summer Triangle frames a bright section of the Milky Way, and with the moon out of the way for the next couple weeks, it’s worth the time to witness this most impressive sight.
I don’t know about you, but winter was too long in the tooth around here, so every time I see those three bright stars and swirly Milky Way I get jazzed for summer nights ahead.