Cygnus the Swan - Northern
Hemisphere
The
celestial swan is sometimes called the northern cross since its +
shape is very striking. Its brightest star Deneb at magnitude 1.3 and
is one of the members of the summer triangle. Although the faintest
of the triangle it is actually is the brightest only appearing
fainter because it is the most distant.
In
mythology Cygnus represents a swan flying down the milky way, swans
feature in many legends including that of Zeus who visited Leda wife
of King Tyndareus of Sparta in the guise of a swan. The result of
their union was Pollux one of the heavenly twins.
Alpha
or Deneb which means ‘Tail of the Hen’ marks the top star of the
northern cross has a magnitude of 1.3 and is a class A2 supergiant
star with a surface temperature of around 8,000’C much hotter than
our Sun, It lies at a distance of 2,600 light years.
Beta
or Albireo or the ‘Hen’ is at the bottom star of the cross of
Cygnus it has a brightness of magnitude 3.2, it is an orange K2 giant
star and is 430 light years away. If you have a small telescope or a
pair of binoculars you will see that Albireo is actually a double
star with the companion star being a much hotter B class giant star
of magnitude 5.1.
Gamma
or Sadr which means ‘Breast’ is the middle star of the cross. It
is brighter than beta with a magnitude of 2.2 at a distance of
around 1,800 light years. It is a F8
supergiant star slightly cooler than the Sun.
To
the left of gamma is epsilon or Gienah which means ‘Wing’. It is
73 light years away and
shines at a magnitude
2.5. It is an orange K0 giant star indicating it is cooler than the
Sun.
If
you look to the right of gamma you will see delta which has no name.
It is of magnitude 2.9 and is 165 light years away. It is an A0 class
star.
Between
gamma and beta is the variable star chi which can vary in brightness
from magnitude 3.3 when it is easy to see down to magnitude 14.2 when
a large telescope will be need to see it. Chi is a Mira type variable
star named after omicron ceti or Mira the prototype star of this
class of variable stars. It is a M6 giant class star, much cooler
than the Sun.
Messier
or M39 is an open cluster that
can be seen as a fuzzy
light patch of light north of Deneb shining at a magnitude or 4.6. It
was first recorded
by Aristotle in 325 BCE. M39 lies about 950 light years away and only
contains about 30 stars.
NGC
7000 or the North American Nebula was discovered by William Herschel
in 1786. This nebula is lying close to Deneb. Some people claim it
may be visible to the naked eye under good, dark conditions, and a
preferred object for amateur astrophotographers. Its mag is 4.4 but
spread over a wide area.
It
is called the North American nebula because it has the same shape as
North America and is a great favourite with astronomers to
photograph. It was first photographed by Max Wolf on December 12,
1890.
The
distance to the North America Nebula is estimated at 1,600 light
years.
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