Stardate 03:15:98
Open Cluster Celebration
Last week, we talked a little about open clusters,
and got to examine two of them, the famous Double Cluster in Perseus.
Open clusters are groups of perhaps 10 to a few
thousand stars. The stars inside of open clusters are young to middle aged,
and the groups are among the youngest of any groupings of stars in the
sky. These stars are spread in a rough grouping anywhere from thirty to
ninety light years across.
This week, we will take a more detailed look at
some of the open clusters currently visible in the sky. All four of these
objects were first cataloged by Charles Messier, an unsucessful comet hunter
whose catalog of mistakes became one of the most widely used astronomical
catalogs of all time. Anytime an object is listed with a name having an
M beginning, such as M31, the object was recorded in Messier's catalog.
Originally containing 110 objects, two of the objects were later trimmed
from the list, bringing the number of Messier objects down to 108.
The open clusters we will be viewing this week
(weather permitting, of course) are the objects M35, M36, M37, and M38.
All of these objects are just barely visible to the naked eye from the
darkest of skies. With any telescope, or, in this case even better, a pair
of binoculars, we can easily bring these ancient star clusters to our backyards.
First, go outside about 8 pm, and face to the
west. Nearly directly overhead are two bright stars, near one another.
The brighter of these will appear redish. These are the stars Pollux (brighter)
and Castor (the dimmer of the two). These are both the heads of the two
twins of Gemini.
Now, looking down towards the west, you should
see a diamond of other bright stars. The one towards the southwest is Betelgeuse
in Orion. The bottom star, nearly due west is Aldebaran, and very bright.
This is the gleaming red eye of Taurus, the bull with whom Orion is perpetually
locked in mortal combat.
Lastly, the diamond is completed by Capella to
the north. The first object we willl view is M35, also known as NGC 2168.
This cluster is magnitude 5, and can be found nearly directly in the middle
of the triangle we discussed above. This places the object some 60 degrees
above the horizon as seen from New England, or any other area about 42
degrees north latitude. This object spans nearly 1/2 degree across the
sky, making it seem as large across as the Sun, or a full Moon. From here,
travel nine degrees to the north west. Here lies the next object on our
night's viewing list, M37. Nearly as wide as M35, M37 is about 60 percent
as bright as it's sibling cluster. This cluster is also called NGC 2099.
M37 is also about two degrees higher in the sky than M35, resting some
62 degrees above the horizon. From M37, go back down the two degrees, back
to the altitude of M35. then travel about 3 1/2 degrees to the northwest.
Here you will find the open cluster M36, also known as NGC 1960. It has
an apparent diameter only about half that of M37, and is about 30 percent
dimmer.
We end the evening with a peek at M38, or NGC
1912. This object lies only 2 1/4 degrees from M37, again, towards the
northwest. This cluster is nearly twice the angular size of M36, and is
about 30 percent dimmer still. You should now be just a few degrees away
from Capella.