Summer Trianlge Not Just for Summer

Summer Triangle Not Just for Summer
by Rod Kennedy

It is ironic that one of the most prominent asterisms in the sky, the Summer Triangle, is not visible only in summer.  The Summer Triangle is visible well into the fall, and is highest in the sky in August.  One of the most beautiful constellations that makes up part of the Summer Triangle is Cygnus the Swan.

Cygnus the swan is the most eastern of the constellations that make up the Summer Triangle.  Its brightest star is the star Deneb, marks the tail feathers of the Swan.  Deneb is one of the brightest and hottest stars in the night sky.  Deneb lies at a distance of 1600 light years away, which means that is is very, very large and luminous.  By comparison, the brightest star in the sky Sirius is just over eight light years away.  So if Deneb was placed at the same distance away as Sirius it would appear as bright as the full moon.

While Deneb is the brightest star in Cygnus, it is arguably not the most beautiful.  That award goes to Alberio, the star at the nose of the swan.  Through binoculars or a small telescope Alberio reveals itself to be an optical double star.  One star is a deep gold and one a brilliant sapphire blue.  The two stars are too far apart to be a true binary star system (in which the stars orbit around each other) but they appear in the same field of view as seen from Earth.

Deep sky observers will need dark skies to locate two of Cygnus’ most interesting objects.  The first is just east of Deneb.  Through binoculars you can see a faint glow that is slightly brighter than the background of the Milky Way.  A telescope reveals a shape that vaguely resembles the continent of North America.  This then is the North American Nebula.  Timed photographs show a bright pink glow of ionized gas and masks of darker material.  Just east of the easternmost wing tip of the swan is the Veil Nebula, the remains of a super nova explosion.  The Veil is extremely faint and very dark skies combined with a larger telescope will be needed to even catch a glimpse of this rare sight.

While August is typically seen as the last month of summer, there are still plenty of good nights of comfortable weather to observe under.  The constellations of the Summer Triangle, Lyra, Cygnus and Aquila are in the best possible position to observe; that is directly overhead.  And since these constellations lie along the Milky Way, there are plenty of targets for binoculars and telescopes.

August 2011 Chart

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