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Binocular Universe: Next Stop: Andromeda
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Next Stop: Andromeda
Like many of you
this, I am a long-time fan of the original Star Trek television
One of the more unusual episodes to come out of season 2 was
"By Any Other Name." In
this installment, the
introduced more people to the Andromeda Galaxy (also known as M31) and
distance away from the Milky Way than all of the astronomy books and
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
our two eyes as it approaches the sky's zenith.
Light-polluted suburban and urban skies might hide M31 from
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)
yourself, first find its home constellation, Andromeda the princess.
Andromeda is often portrayed as sharing the star Alpheratz with
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
field further northeast to Mirach. Take
a sharp right turn northwestward, first stopping at Mu Andromedae and
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
several hundred billion suns. And
that starlight has been traveling for more than 2.5 million years just
your eyes tonight!
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
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
spiral-arm disk is also visible. M31
reaches out as far as 5° -- that's as wide as ten Full Moons
stacked end to
And it's only going to look larger over time,
show it is getting closer to us. Unlike
most galaxies, which are moving away from us as the universe continues
expand, Andromeda and the Milky Way are locked in a gravitational
that both sides will eventually lose. In
three to five billion years, their mutual gravitational attraction will
the galaxies to collide. Over the ensuing
billion or so years, these two majestic spirals will pirouette around
other, eventually merging into a single, massive elliptical galaxy.
Had Kirk and company continued on their
trek, they would have noticed that Andromeda has several galactic
M31's two largest satellite galaxies can be spotted through
although again each will push your limits. The
smaller and brighter of the pair, M32, can be spotted as a small,
star-like patch of light due south of M31's central core.
The second companion, M110, is larger and fainter, and therefore
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
this as you enjoy the view. As we
gaze contemplatively toward this distant island universe, it's
think that a civilization like the Kelvans just might be staring back
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
certainly not the only galaxy visible in tonight's sky.
In fact, there’s another “nearby” galaxy right
Hop the border from Andromeda to the tiny constellation
Aim toward Triangulum’s apex star, Mothallah, or Alpha
is a great starting point for finding the spiral galaxy M33.
Center Alpha in your binoculars and then look for a faint star
a field of view to the west. Center
on this star, and then look for a very faint glow near the western edge
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
galaxy to our own, M33 can be far more difficult to find than others
farther away. The problem is its
very low surface brightness. When
observers talk about surface brightness, they are referring to the
contrast an object has against the background sky.
M33's contrast is so low that you might pass right over it the
without even noticing it. But with
patience, you'll spot it.
To find our final two targets this month, head
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
star like our Sun, but much bigger: a yellow giant.
The second brightest point in the triangle is a cooler, orange
star. Defocus your binoculars
slightly to amplify their colors.
John Davis, a veteran binocularist from
You'll even find a golf ball just to the east
of Davis's putter. That's actually the
cluster NGC 752.
Look for a round, grayish smudge measuring about as large as the
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
binoculars add several fainter points strung across the core.
Back to the Kelvans.
The episode ended with our fearless foursome overpowering the
by using the Kelvans’s newly discovered human senses and emotions
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
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.
|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.|