Andromeda the
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Andromeda the
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(Aired on the SWAOG Astronomy Net on 12/19/02)
During the early evening hours, Andromeda can be seen almost
directly overhead from the Chicagoland area in December.
Andromeda was the daughter of King Cepheus and Queen
Cassiopeia of Ethiopia. She was chained to a rock and exposed to
the Sea Monster, Cetus, as punishment for her mother's boast of
beauty superior to that of the Nereids. Perseus, on his way back
from his expedition against the Gorgon, saw her and fell in love
with her and promised Cepheus he would free her if she could
become his wife. Cepheus agreed and, with the aid of his
miraculous weapons, Perseus killed the monster and married
Andromeda.
Andromeda appears to be two lines of stars emanating from the
northeast corner of the Great Square of Pegasus. Andromeda is a
long line of fairly bright stars; her head is the star Alpheratz,
which is derived from the Arabic for the “Horse’s
Navel”. Alpheratz used to be the delta star of Pegasus, but
is now the alpha star of Andromeda and shares the northeastern
corner of the "Great Square of Pegasus". Andromeda’s feet
lie near Perseus. Fainter stars represent her outstretched arms
that are chained to the rock. The members of the royal family,
Andromeda, Cassiopeia, Cepheus, and Perseus, lie next to each
other in the sky, partly in the Milky Way. Perseus, who rescued
Andromeda, towers protectively over her, standing with one foot
on the Pleiades. In his hand hangs the awful head of Medusa, the
"Demon of the Woods". Alpha Andromeda is followed by 3 stars
between magnitude 2 and 3, delta, beta and gamma Andromeda, which
form, more or less, a straight line. Another dimmer line of stars
also emanates from Alpheratz. Starting with the stars pi and mu
Andromeda, they form an acute angle with the brighter line.
In last month’s report on Cassiopeia, you learned how
you can use the alpha, beta, and gamma stars of Cassiopeia to
form sort of an ‘arrow-head’ pointer to help you find
the Andromeda Galaxy. Download the latest copy of the Monthly Sky
Map from www.Skymaps.com, and
go outside on the next clear night and see if you can find it.
Let us know if you were successful!
The Andromeda Galaxy is the farthest object than can be seen with
the naked eye. It is 2.3 million light-years away. This means
that the light that you are seeing left the galaxy 2.3 million
years ago. It took that long for the light to travel from the
galaxy to your eyes!
The Andromeda galaxy is 130,000 light-years wide, about twice the
size of our own Milky Way galaxy. It too is a spiral galaxy with
two arms emerging from a central core, and it contains over 300
billion stars. Two smaller galaxies, M32 and M110, which can be
seen through small telescopes, accompany M31, the Andromeda
Galaxy.
NGC 752 is an open cluster of around one hundred stars. It is about four and a half degrees south, and two degrees west of gamma Andromeda.
NGC 891 is rather faint, but a nice edge-on spiral galaxy with
clearly distinguished dust-lane in large telescopes. It is four
degrees east of gamma Andromeda.
NGC 7662 is called the "Blue Snowball" nebula. This is a
bluish-green planetary nebula with a very faint central star,
which is variable. It is estimated to range between magnitude 12
and 16. The "Blue Snowball" nebula is found about 2.5º
West-Southwest of iota Andromeda.
If you like a challenge, try to find M33, the Pinwheel Galaxy, in
the neighboring constellation of Triangulum. It’s a little
tough to find in the light-polluted skies of the Chicago
Metropolitan Area.
Go out and view the constellation Andromeda and some of its
wonders, and let us know what you think!
- Jeff B.
Copyright © 2002 South West Astronomy Observers Group