Mohawk Valley Astronomical Society

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The Christmas Cross

by Perry Pezzolanella, MVAS

The crisp autumn evenings are an excellent time to observe as the haze of summer is gone and the stars seem to sparkle brighter. One of the best constellations to observe is Cygnus, the Swan, since it is easy to locate flying nearly overhead along the hazy band of the Milky Way. With the bright stars Albireo marking its head, Deneb marking its tail, and several other bright stars defining its wings, Cygnus is commonly known as the Northern Cross and closely resembles its smaller cousin, Crux, the Southern Cross.

With the star chart that follows, the first gem is probably the most beautiful double star of all, Albireo. This star shines at magnitude +3.1, and with nothing more than a low power eyepiece on a telescope, Albireo will be split into a pair revealing a magnitude +5.1 companion. The brighter star burns a warm, golden hue while the fainter star displays a striking color contrast as cool, bluish-white. Albireo is by far the best of the stars to show at a star party.

The North American Nebula, NGC7000, is close to the bright star, Deneb and the resemblance to our continent is striking. The Gulf of Mexico, Florida, and Central America regions are the brightest and thus the easiest to recognize. Patience and a telescope with very dark skies and properly dark-adapted eyes will be required to see the entire nebula.

The Veil Nebula, (NGC6990, 6692, and 6995) a supernova remnant, is a beautiful sight in a small telescope. It can be found about halfway between the stars Epsilon (ε) and Zeta (ζ) Cygni. Fine detail such as fingers and feathers of individual curving arcs seen under ideal skies is convincing that something exploded. A wide-angle eyepiece at the lowest power will encompass the entire nebula.

A large, broken nebula, IC1318, surrounds Gamma (γ) Cygni. A wide-angle eyepiece will reveal the complexity of this nebula, which encompasses three brighter patches. Within it and close to Gamma Cygni is a small star cluster, NGC6910, which appears like a tiny “Y” anchored by two golden 7th magnitude stars.

Not far from Gamma Cygni is another small cluster, M29, which appears like a tiny version of the Pleiades. It can be hard to locate as it is so small and buried within the Milky Way, but its shape will aid in identifying it. Above Deneb is a more obvious star cluster, M39, which has many more stars and a good mixture of bright and faint stars in the shape of a triangle.

A bizarre object worth observing is NGC6826, better known as the Blinking Planetary. It looks like an ordinary star, but increase the power and the fun begins! The star is actually surrounded by a bluish-green, planet-like disc under higher power, but can only be seen by looking a little off to one side of the star. Staring directly at the star makes the nebula disappear. This is because the more sensitive area of the retina is off to the side making it easier to see dim objects such as nebulae. Moving the eye back and forth between the star and the edge of view will create a blinking effect.

There is so much more to see in Cygnus and a good star chart will lead the way to many more rewarding hours of observing. While Cygnus is nearly high overhead during the late summer, it becomes lower as autumn progresses. By December, the evening sky is graced with a large, beautiful symbol of a nearly perfect cross standing upright with Albireo at it base near the northwest horizon, signaling the arrival of the Christmas season.