The Summer Triangle Rides Again

The Summer Triangle appears in the eastern sky at nightfall in late June, rising ever higher through the night. The band of the Milky Way slices diagonally through the figure coursing from southeast to northeast. Created with Stellarium

Now that we’ve finally bridged the solstice and embarked on our journey into summertime, it seems fitting to get re-acquainted with the Summer Triangle. I noticed it last night when my younger brother and I stepped out to watch the space station pass by.

As you might expect for a triangle, three stars join forces to create the huge figure in the eastern sky at nightfall. The brightest and one of the first stars to come out during twilight 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. You can’t miss it about halfway up the eastern sky at nightfall.

All three look like points of light, but if we could see them up close, we'd discover that Altair (17 light years distant) is about twice the diameter of the sun, Vega (25 light years) about three times and Deneb (~2600 light years) is a supergiant star 200 times as big. Altair and Vega rotate rapidly causing them to bulge out at their equators. Illustration: Bob King

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. Being first magnitude or brighter, Vega, Deneb and Altair are all easy to see; city and suburban observers should have little difficulty in finding them.

An additional treat awaits the eyes of rural observers or those who make a drive to the country. The Summer Triangle hosts a bright section of the Milky Way, and with moonless skies the entire week ahead, it’s a most impressive sight. This is especially true for those living in mid-northern latitudes. The lower half of the Milky Way in Sagittarius, while equally amazing, never gets high enough above the horizon haze to grab your attention the way the northern half does. Many a night I’ve stood back and watched the Summer Triangle and its strands of starry haze waft overhead accompanied by the gentle clatter of leaves in the breeze. The vastness of it all becomes palpable.

4 Responses

  1. thomas s

    hi again bob. talking about the Swan/Northern Cross reminds me that, as I recall, there is a beautiful little double (don’t remember whether it is a binary or a visual) at the end of the Swan (or the foot of the cross). one is blue and the other is distinctly orange. was it albireo? (sp?) it can be seen easily with binocs or a small telescope. long time since I looked, so memory may be a bit shaky. so am I right or no?

  2. Luna

    Hi, I was wondering about the stars, Vega & Altair. Some people and webs say that the stars meet once a year. What does that mean? Can you please explain about it? I’m writing an assignment about these stars, so thanks a lot! Don’t worry, I’ll put the web name on the sources. Thanks again!

    1. astrobob

      Hi Luna,
      Thanks for writing. I’m not exactly sure what you mean about Vega and Altair, but they don’t move across the sky and come together. They’ve been in pretty much the same spot for several thousand years. But they do appear in the evening sky together late at night in April – Vega in the northeast and Altair in the east. In summertime and fall, they’re both high up in the south at the end of evening twilight.

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