Astronomer’s Corner

Written by Ted Forte

Don’t let the nickname fool you. The area of the sky defined by the “Summer Triangle” takes center stage in Autumn. The stars Vega, Deneb, and Altair, the brightest stars in the constellations of Lyra the Harp, Cygnus the Swan and Aquila the Eagle form a recognizable triangle that transits (is due south in the sky) on fall evenings. Within and around this triangle are some of the sky’s most fascinating targets. 

About a third of the way along a line connecting Altair and Vega sits a fun binocular asterism. Known as the “Coat Hanger”, its proper designation is Collinder 399. The brightest 10 stars in this open cluster form the unmistakable image of a wire coat hanger. 

Forming a smaller triangle, with and about equidistant from Vega and Deneb, is the star that forms the head of Cygnus the Swan. It’s named Albireo and designated Beta Cygni. The beta star of a constellation is usually its second brightest star, but in this case, Albireo is the fifth brightest star in Cygnus. Albireo is one of the loveliest double stars in the heavens. An amber 3.1 magnitude primary is paired with a blue 5.1 secondary 35” away. The pair is about 420 light years distant from Earth. 

About 1.7o northeast of Vega is a multiple star system known as the “Double Double” and designated Epsilon Lyrae. Appearing as a single star to the naked eye, your finder scope or binoculars will show it as two stars, approximately 5th magnitude and separated by 3.5’. A telescope in good seeing conditions will reveal that each component of the pair is itself a close double. The north pair is magnitude 6.0 and 4.7 and the south pair are almost equal at about 5th magnitude. Both binaries are just 2.4” apart. The whole system is about 162 light years away.

Binoculars or a wide-field low power telescope will show the “North American Nebula” as a faintly glowing mass directly east of Deneb. So named because its brightest section mimics the Atlantic coast line of North America, it’s officially named NGC 7000. This vast cloud of ionized hydrogen gas is probably about 2,500 light years away.  A UHC (ultra high contrast) filter will greatly enhance the visibility of the nebula and may even make the adjacent “Pelican Nebula” visible as well. 

A filter is a must to enjoy the supernova remnant known as the Veil Nebula. This amazing nebulous complex is the remains of a star 20 times more massive than the sun that exploded about 15,000 years ago. Sections of the Veil have earned their own designations. The two brightest arcs of nebulosity are known generally as the Eastern Veil, NGC 6992, and the Western Veil, NGC 6960. The entire complex is three degrees across and covers an area 36 times the size of the full moon. It probably lies about 2,400 light years away. The Veil is located below the eastern wing of Cygnus. The Western Veil is adjacent to the 4.2 magnitude star 52 Cygni which lies just over 3 degrees south of Epsilon Cygni which marks the tip of the eastern wing. The Eastern Veil is found by moving straight east from the northern tip of the Western Veil about 3 degrees.

The Summer Triangle is home to two of the most famous planetary nebulae in the sky. Planetary nebulae are a late evolutionary stage of sun-like stars. These stellar corpses consist of a glowing circumstellar cloud of ionized gas surrounding an extremely hot central star. The central star is the exposed core of the original star and the glowing cloud that surrounds it is the expelled outer layers of that star. 

Messier 27, also known as the “Dumbbell Nebula” was the very first planetary nebula discovered and, at 1,360 light years, is one of the closest to Earth. You’ll find it 3.20 north of Gamma Sagittae which represents the tip of the arrow. Named for its distinctive dumbbell or apple core shape, it’s large and bright and a popular target for amateur astronomers. 

The “Ring Nebula” or Messier 57, is a star party favorite. It’s small, but very bright and well defined and looks like a ghostly celestial donut or a smoke ring. It’s nestled midway between Beta and Gamma Lyrae, the two stars that form the base of the harp asterism, making it quite easy to find. Based on the number of times I’ve turned a telescope to this little jewel, I’d have to say this is my favorite object in the entire sky! M 57 is about 2,300 light years away. 

These objects are just a sampling of the deep sky splendors that can be found in the area defined by the Summer Triangle.