cygnus the swan
By Mike Barrett
Cygnus, The Swan, is a majestic and easy to identify
constellation in the northern hemisphere. This is best
viewed in summer and autumn when it rises overhead
in the night skies. Cygnus is a great naked eye
constellation with lots of detail and great objects within
it as you start to use more powerful optical devices.
The brightest star in the constellation, Deneb, is
magnitude 1.25 the third brightest in the region. Deneb
combines with Vega (in Lyra) and Altair (in Aquila) to
form the summer triangle. These 3 stars are the first to
appear in the darkening sky after sunset.
Deneb is also the head of an asterism called the
Northern Cross which forms the body and the first part
of the wings of the swan. The stars in this cross are the
brightest ones in the constellation and can be seen
even in the most light polluted areas.
As you move to darker locations you will be able to
see more stars in the constellation which extend the
wings of the swan right out to the wing tips. Cygnus is
one of the constellations that is easy to visualise, and
once you have found it you will never forget it.
In the darkest viewing spots when there is no moon
you will be able to see our galaxy, The Milky Way,
running through Cygnus. It will appear as a cloud
starting at the horizon, going up through Cassiopeia
then Cygnus and on to the other horizon in Scorpius.
The cloud-like appearance comes from the millions of
faint stars in our galaxy combining to create the dim
light.
If you now grab a pair of binoculars you will see the
detail of the Milky Way. Stars will pop into view that
were not visible with your naked eyes. Even in the
binoculars though there will seem to be a fuzzy cloud
created by the fainter stars.
If you sweep the binoculars down to the head of
the swan you will find the star Alberio. Star is not quite
the right term as Alberio is one of the most spectacular
double stars in the skies. With a steady hand and a
good pair of binoculars you should be able to separate
the two stars. The main star is yellow, but the smaller
star is electric blue.
Switching to a telescope makes the demarkation
between these stars much more noticeable and can
really bring out the colours nicely.
There are a lot of deep sky objects in the constellation,
but by far the most interesting are NGC 7000 and IC
5070: The North America and Pelican Nebulas. These
can be seen from very dark locations using telescopes
and appear a very faint foggy regions, but are best
observed photographically. The nebulas are huge,
the North America nebula is over four times the size
of the moon, but very faint. These are star forming
emission nebulas of ionised hydrogen. These nebulas
lie between Deneb and Epsilon Cygnus.
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