There's a special treat waiting for you this Halloween.
Remember how, in the Peanuts cartoon, Linus would wait
every Halloween for
the Great Pumpkin to appear in his pumpkin patch? Well, this Halloween there is
a nice big orange pumpkin of sorts right in the middle of the Beehive star
cluster in Cancer.
To receive this treat, all you have to do is stay up past
midnight on Halloween and look for the planet
Mars, now becoming quite bright at magnitude 0.4.
If you haven't looked at Mars lately, you'll be surprised
at how bright it's grown. It now equals the bright star Betelgeuse in
brightness, shines significantly brighter than nearby Castor, Pollux, and
Regulus, and is exceeded only by Sirius (the brightest star in the sky),
Capella, Rigel and Procyon.
Mars typically appears orange or ruddy compared to other
planets and the stars. In a small telescope, it becomes a fuzzy orb rather than
just a point of light.
Zeroing in on Mars with binoculars or a telescope will show
that it is embedded in the beautiful open star cluster, number 44 in Messier's
catalog, known as the Beehive. At 590 light-years distance, it is one of the
closest star clusters to the sun. It's also unusual in that it shines brighter
than any of the individual stars in the its constellation, Cancer.
The Beehive seems an appropriate name, since the cluster
resembles a swarm of glowing bees. Its alternate name, Praesepe, is a bit more
puzzling. It is Latin for "manger" and relates to an alternate version of the
constellation Cancer, where two nearby stars, Asellus Borealis and Asellus
Australis, are named for donkeys, gathered around the central manger.
If you observe Mars with a telescope, take careful note of
its exact position against the background stars of the Beehive, perhaps making
a simple sketch. An hour or so later, check the position again, and you will
see that it has moved slightly. There's even a chance that from your particular
location Mars, in its orbit around the sun, will actually pass in front of one
of the Beehive's stars, causing an occultation.
Besides growing brighter, Mars is also increasing in size
as it moves towards opposition, the point opposite the sun in the earth's sky,
on 2010 Jan. 29.
At present Starry
Night shows it to have a diameter of 7.9 arcseconds at a distance of 1.182
astronomical units. 7.9 arcseconds is only 0.4 percent of the moon's diameter,
equivalent in size to a tiny crater on the moon. An astronomical unit is the
average distance from the Earth to the Sun: 93 million miles, making Mars 110
million miles from Earth. By Jan. 29 it will have almost doubled its size to a
diameter of 14 arcseconds at a distance of 0.664 astronomical units, a mere 62
million miles away.
The coming opposition of Mars is known as an aphelic
opposition, since it occurs close to Mars' aphelion (its greatest distance from
the sun). Compare its size with what it was in August 2003, a very favorable
perihelic opposition: 25 arcseconds and only 0.373 astronomical units away.
This
article was provided to SPACE.com by Starry Night Education, the
leader in space science curriculum solutions.
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