This month look for the star, Alpheratz, the lucida of
Andromeda. Alpheratz is one of only a
few stars that connect two constellations together; in this case, Andromeda and
Pegasus. Alpheratz passes just south of
the overhead position at 9:00 PM in early November and about two hours earlier
in late November. Alpheratz is 97 light
years, so if you were born in 1919, Alpheratz is your birthday star this
year.
Alpheratz is classified as a “B” star, which is the second
hottest class of star (only “O” is hotter).
The surface temperature of Alpheratz is approximately 13,000 degrees C,
or about 23,000 degrees F. The total amount of radiation produced by the
surface of Alpheratz is 200 times greater than our Sun. To be a main sequence star that’s hotter than
our Sun, Alpheratz must also be more massive than out Sun. Therefore Alpheratz will live a shorter life
than our Sun.
Alpheratz is our jumping off point to find the Andromeda
Galaxy. In dark skies you can see
Andromeda Galaxy without optical aid. In
moderately lit skies, it can easily be found with a pair of binoculars. Andromeda Galaxy has also been given the name
of M-31. Centuries ago, people had
noticed the fuzzy looking star in the constellation of Andromeda. Little did they know that it was a great
island of over 100 billion stars, located some 2,500,000 light years away.
To find M-31, begin at Alpheratz. The bottom three stars of Andromeda are her
brightest and form a gentle arc. The
star closest to Alpheratz is not particularly bright, but the next star,
Mirach, is. Locate Mirach in your
binoculars and put it in the lower right side of the binoculars (7X50’s) as
illustrated below. In the middle of the field
of view will be the fainter Mu Andromedae and above that, Nu Andromedae will be
close to the opposite edge of the binoculars.
Look next to Nu and note the fuzzy looking star. This is the Andromeda Galaxy. Once you have located it in binoculars, try
locating it using just your eyes. You’ll
need reasonably dark skies to see M-31.
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