Like many of you
reading
this, I am a long-time fan of the original Star Trek television
series.
One of the more unusual episodes to come out of season 2 was
entitled
"By Any Other Name." In
this installment, the Enterprise was commandeered
by the Kelvans, an advanced race who recently assumed
human form for their devious purpose. After
the rest of the crew had been reduced to
small cubes of chemicals, Kirk, Spock, McCoy, and Scotty were forced to
pilot
the Enterprise
toward the Kelvans' home in the Andromeda
Galaxy. Even with modifications,
the
Enterprise
would take 300 years to make the
trip.
That episode
probably
introduced more people to the Andromeda Galaxy (also known as M31) and
its vast
distance away from the Milky Way than all of the astronomy books and
articles
ever written about it. The idea that
it would take a super-charged Enterprise three centuries to get there
points to the enormity of intergalactic space.
Yet, with pristine conditions, we can see this galaxy tonight
with just
our two eyes as it approaches the sky's zenith.
Light-polluted suburban and urban skies might hide M31 from
naked-eye
view, but it can still be spotted through carefully aimed binoculars.
Above: Autumn star map from
Star
Watch
by Phil Harrington.
Above:
Finder chart for this month's Binocular Universe.
Chart
adapted from Touring
the Universe
through
Binoculars Atlas (TUBA)
To find
M31 for
yourself, first find its home constellation, Andromeda the princess.
Andromeda is often portrayed as sharing the star Alpheratz with
Pegasus,
where it marks the northeastern corner of the Great Square. From Alpheratz, slide about one
binocular field northeast, to the faint star Delta Andromedae, and then
another
field further northeast to Mirach. Take
a sharp right turn northwestward, first stopping at Mu Andromedae and
then
onward to Nu Andromedae. Finally,
look just northwest of Nu for an elongated blur of dim light.
It may not look like much at first, but that's the combined
light of
several hundred billion suns. And
that starlight has been traveling for more than 2.5 million years just
to reach
your eyes tonight!
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Left: M31, the Andromeda
Galaxy, along with M32
(below) and M110 (above), as sketched through the author's 10x50
binoculars. North is up. |
The Andromeda Galaxy is the closest major
galaxy to our
Milky Way and the brightest visible from the Northern Hemisphere.
Binoculars show it as a broad, oval smudge of grayish light
highlighted
by a prominent core. How much of the
galaxy your binoculars will show depends on sky clarity and darkness.
Only the central nucleus is bright enough to pierce severe light
pollution, but from a dark, rural location, the full span of the
extensive
spiral-arm disk is also visible. M31
reaches out as far as 5° -- that's as wide as ten Full Moons
stacked end to
end!
And it's only going to look larger over time,
as studies
show it is getting closer to us. Unlike
most galaxies, which are moving away from us as the universe continues
to
expand, Andromeda and the Milky Way are locked in a gravitational
tug-of-war
that both sides will eventually lose. In
three to five billion years, their mutual gravitational attraction will
cause
the galaxies to collide. Over the ensuing
billion or so years, these two majestic spirals will pirouette around
each
other, eventually merging into a single, massive elliptical galaxy.
Had Kirk and company continued on their
intergalactic
trek, they would have noticed that Andromeda has several galactic
groupies.
M31's two largest satellite galaxies can be spotted through
binoculars,
although again each will push your limits. The
smaller and brighter of the pair, M32, can be spotted as a small,
almost
star-like patch of light due south of M31's central core.
The second companion, M110, is larger and fainter, and therefore
more
difficult to observe. Look for it to
the north of M31's core, about twice as far as M32.
Both are classic examples of dwarf elliptical galaxies.
M32 looks almost perfectly circular, while M110 is more oblate.
M31 is a real treat through binoculars, but
consider
this as you enjoy the view. As we
gaze contemplatively toward this distant island universe, it's
interesting to
think that a civilization like the Kelvans just might be staring back
at us
through their own alien binoculars, wondering if you and I exist.
A thought to ponder as we gaze skyward this month.
The Andromeda Galaxy may be the brightest, but
it is
certainly not the only galaxy visible in tonight's sky.
In fact, there’s another “nearby” galaxy right
nearby.
Hop the border from Andromeda to the tiny constellation
Triangulum.
Aim toward Triangulum’s apex star, Mothallah, or Alpha
Trianguli. Alpha
is a great starting point for finding the spiral galaxy M33.
Center Alpha in your binoculars and then look for a faint star
about half
a field of view to the west. Center
on this star, and then look for a very faint glow near the western edge
of the
field. That's M33.
What's that? You
don't see it? I'm not surprised.
Even though, at 3 million light years, it's the second closest
major
galaxy to our own, M33 can be far more difficult to find than others
many times
farther away. The problem is its
very low surface brightness. When
observers talk about surface brightness, they are referring to the
level of
contrast an object has against the background sky.
M33's contrast is so low that you might pass right over it the
first time
without even noticing it. But with
patience, you'll spot it.
To find our final two targets this month, head
northwest
from Delta to Beta Trianguli, and continue across the border back into
Andromeda. About a binocular field
beyond Beta, you'll bump into a slim triangle of stars.
The brightest star of the three, known as 56 Andromedae, is also
a yellow
star like our Sun, but much bigger: a yellow giant.
The second brightest point in the triangle is a cooler, orange
giant
star. Defocus your binoculars
slightly to amplify their colors.
John Davis, a veteran binocularist from Amherst,
MA, sees a golf putter when he
looks here.
He suggests that the triangle itself marks the head of the
putter, while
a line of four other suns tilting northward make up the club's shaft.
Because of the stark surroundings, the putter asterism stands
out nicely.
You'll even find a golf ball just to the east
of Davis's putter. That's actually the
open
cluster NGC 752.
Look for a round, grayish smudge measuring about as large as the
Full
Moon. While most binoculars resolve only the group's brightest sun, a
9th-magnitude orb just to the south of the cluster's center, 70-mm and
larger
binoculars add several fainter points strung across the core.
Back to the Kelvans.
The episode ended with our fearless foursome overpowering the
highjackers
by using the Kelvans’s newly discovered human senses and emotions
against
them. It’s tough to be a human,
but once again, the United Federation of Planets was saved!
There’s more to this month’s
Binocular Universe, as
you can see from the list below.
Live long and prosper.
And remember that, whether Kelvan or human, two eyes are better
than one.
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About the Author:
Phil
Harrington has written 9 books on astronomy, including Star Ware,
Star
Watch, and his latest, Cosmic Challenge. Visit his
web site, www.philharrington.net,
for more
information.
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| Phil
Harrington's Binocular
Universe is
copyright 2012 by Philip S. Harrington. All
rights reserved. No
reproduction, in whole or in part, beyond single copies for use by an
individual, is permitted without written permission of the copyright
holder. |
