Stardate:05:10:98
How Many Galaxies can be Packed into One Area
of Sky?
This week, we will begin to view one of the most
galaxy rich areas of the sky.There are so many wonderful objects in this
region, it is impossible to cover them all in this article in only one
week. Just a few degrees apart, in the east/southeast sky just after the
Sun sets, lies a large goldmine of galactic wonder.
This is a treat best appreciated with a large
pair of binoculars, or a telescope with very low magnification. If you
choose to use binoculars, you will want to use a pair having an objective
lens of at least 50 mm. This can be read as the second in the pair of numbers
which are commonly used to describe the magnification and light gathering
ability of a pair of binoculars. A pair listed as 10X50 will have a magnification
of 10 power, and objective (main) lenses with a diameter of 50 mm. It is
especially useful to get out under dark skies this observing sesssion,
particularly if using binoculars. If you choose instead to use a telescope,
make sure to use an eyepiece with a long focal length, 25 mm or more. A
40 mm eyepiece would be perfect. Eyepieces which have a long focal length
provide very low magnifications in telescopes, along with a wide field
of view (how much can be seen at one time), and bright images.
Go outside, and look toward the east/southeast
sky around 9 pm. Now look about 50 degrees above the horizon. There is
a large field of galaxies which begins here. These galaxies spread across
20 degrees of sky, starting in the east/southeast, and progressing upwards,
and towards the east. Almost all of these galaxies, however, are crowded
within the 10 degrees in the center. The galaxy at the bottom, 50 degrees
above the east/ southeast horizon is M61. Also known as NGC 4303, it is
a spiral galaxy. A challenge for a small telescope, but not impossible
to find, it shines at magnitude 9.7. This galaxy, in many ways like our
own, is seen from Earth to be about 6 arcminutes, or 1/10 of a degree across.
Now travel four degrees, nearly straight up, to
lay your sights on M49. Also called NGC 4472, it is a round galaxy, with
a bright core. At magnitude 8.4, it is well over three times brighter than
M61. Larger in apparent diameter as well, M49 spans 9 arcminutes across,
nearly twice as wide across as M61. Less than one degree to the east of
M49 lies two smaller, dimmer galaxies, NGC 4535, and NGC 4426. NGC 4535
is another round galaxy, with a brightness of magnitude 9.8, and seeming
to have a size between that of M49 and M61. NGC 4426 is an elongated galaxy,
which often is the result of a galaxy having a past gravitational encounter
with another galaxy. This galaxy appears just slightly larger and brighter
than NGC 4535.
Now, continue in your journey another four degrees
above the horizon, and one degree east. Here lay two more galaxies, each
less than 1/2 degree away from one another. These are M59, and M60. M59
is another elongated galaxy, which also goes by the name NGC 4621. It the
same brightness as NGC 4535 which we looked at earlier, but is only 5 arcminutes
(1/12 of a degree) across. M60 is less of a challenge to find, at magnitude
8.8, and it is seen 40 percent wider across than M59. This galaxy is a
round galaxy, and is also known as NGC 4649. On the way to spot the last
two galaxies, did you stumble across two small, dim galaxies? These are
NGC 4596, and NGC 4442.
When you go out to view this area of sky, bring
a good star map with you, and see how many of these objects you can recognize.