One of my favorite summertime celestial treats is the “Summer Triangle”. While the Summer Triangle can be seen from late spring through late fall, its most glorious season is summer while high overhead.
The Triangle is not a constellation but rather the three brightest stars in three of the most prominent summer constellations. The stellar members of our Summer Triangle are Altair in constellation Aquila, the Eagle; Vega in Lyra, the Harp and Deneb, the brightest star in Cygnus, the Swan.
You’ll find Cygnus, Lyra, Aquila and our Summer Triangle high above the eastern horizon as darkness falls in late August and early September. If you venture out around 11 pm look directly overhead (astronomers call this zenith) and see if you can spot our illustrious trio.
Chart courtesy Smoky Mountain Astronomical Society. Click to enlarge
Look carefully at the charts. If you’re out observing before midnight and facing east Vega will be on “top” of the triangle, Deneb to your left and Altair the right.
Altair is the nearest of the trio at a distance of 17 light years. When you look at Altair you’re seeing photons (light) that left the star 17 years ago. It’s about one and a half times the size of our Sun and 10 times brighter. Altair is one of the Eagle’s “head” stars, or at least its portrayed that way in the star charts. I have another vision of the Eagle which I’ll share in a moment.
Vega is the next closest at 24 light years distant. When you see it tonight you’re seeing it as it appeared 24 years ago! Lyra, the Harp is a small parallelagram shaped constellation. If you’re fortunate enough to be doing your stargazing at a relatively dark location and have a telescope look for M57, the Ring Nebula, at the base of the Harp opposite Vega. M57 is a very faint “smoke ring” remnant of a super nova. By the way Vega is the star Jodi Foster “beamed” to in the movie “Contact”. It is about twice the diameter of our Sun and 50 times brighter. Chart prepared using Stellarium freeware. Click to enlarge chart
The third star in our Summer Triangle, Deneb, is spectacular by all comparisons. Deneb means “tail” in Arabic and the star marks the tail of the beautiful stellar swan, Cygnus. I’ve also found varying estimates of Deneb’s distance from our little corner of the galaxy.
In his 1952 book “The Stars: A New Way to See Them” author H.A. Rey placed Deneb at a distance of 50 light years. Other star charts and books published in the past decade list Deneb’s distance at 3,200 light years. More recent charts and data place the star at 1,500 light years distance. Regardless of Deneb’s distance, its size and brilliance are astonishing. Deneb is thought to be 115 times larger and 55,000 times brighter than our Sun! If it were as near as Vega or Altair it would be the brightest star in the sky, bright enough to cast a shadow similar to the first quarter Moon and would likely be visible during daylight!
As mentioned earlier Deneb marks the tail of Cygnus, the Swan. The Swan’s wingspan and body are also known as the “Northern Cross”. Albireo, the Swan’s “beak” is a beautiful blue/orange double star. Use the chart and try to define the shape of the Swan.
My vision of the Eagle varies from the way he is portrayed in the star charts. Most show the constellation with Altair and the star Tarazed as the Eagle’s head and our celestial Accipitridae flying toward the Swan. I see the Eagle winging its way south and west flying in formation toward the heart of the Milky Way with the Swan.
As promised here is the last video episode “Star Hustler” Jack Horkheimer produced and its all about celebrating the Summer Triangle.
Clear skies! Mark, the Stargeezer
I was saddened to learn of the recent passing of the “Star Hustler” or “Star Gazer” Jack Horkheimer. Jack was the Executive Director of the 
