Stardate:04:26:98
Tour of the Galaxies
The universe is a very large place.
When you go to a dark country sky, on a clear, moonless night, all the
stars in the sky number perhaps 5000 stars at any given time. This is about
the number of grains of sand in a small handful of sand. But, the number
of stars in the visible universe is greater than the number of all the
grains of sand on all the beaches on the face of the planet Earth.
The family of stars in which our Sun belongs is the Milky Way galaxy.
The number of stars in our galaxy alone is equal to about the number of
grains of sand in two large dump trucks. There are perhaps 100 billion
galaxies in our universe. This week, we will go on a tour of 10 of these
galaxies in the east/northeast sky.
Go outside around 9 pm. These galaxies form an upside down "L"
whose bottom end is nearly exactly east/northeast, and 56 degrees above
the horizon. Here, you will find a bright, large, spiral galaxy. This is
the spiral galaxy M101. Also known as NGC 5457, it shines at magnitude
7.7; far dimmer than can be seen with the naked eye, but an easy target
for the amateur astronomer. This is one of the most popular objects for
viewing at star parties. M101 has an angular size of about 27 arcminutes,
or nearly half a degree across.
Next, head north nearly 7 1/2 degrees, and just about three degrees
up. Here is another bright, popular spiral galaxy, much like the Milky
Way, but larger. This is known as M51, or the Whirlpool galaxy. The Whirlpool,
as it is known, is dimmer than M101, shining at magnitude 8.4. This is
a circumpolar object, meaning it never sets, and is visible year round.
Five and three-quarters degrees away from M51 lies The Sunflower galaxy.
This is also called M63, or NGC 5055. This is an elongated galaxy with
a bright core. At magnitude 8.6, and a respectable 1/5 of a degree across,
it should make a fairly easy find, above and to the north of M51, sitting
62 degrees above the horizon.
Next, we will turn our attention to M94. You can find this elongated
galaxy 66 degrees above the horizon, and about 2 1/2 degrees north of M63.
Brighter than the last object we viewed, M94 appears nearly as large. About
4 degrees straight above M94 is another spiral galaxy, known as NGC 4490.
This is where we make the "bend" in the "L". It would
be quite a challenge to see this galaxy with the popular 60mm size telescope,
as it is nearly magnitude 10. A larger telescope, or a pair of binoculars
with a very large pair of objective lenses should reveal it's elegant body.
About two degrees to the north, and up one more degree reveals NGC 4449.
It is brighter than NGC 4490, at magnitude 9.4. Both of these objects also
appear small, about 1/10 of a degree across.
Next, continue the trip along the top of the upside down "L",
traveling 3 1/2 degrees to M 106. This is another circumpolar object, and
a spiral galaxy. At 18 arcminutes across, it spans nearly 1/3 of a degree.
Keep in mind, the full Moon and the Sun span only about 1/2 a degree across
each as seen from Earth. M106 is a spiral galaxy with bright knots, and
is magnitude 8.3, about 2 1/2 times brighter than M51 or M94.
On our way to our final destination, M109, we will quickly encounter
two dim, small galaxies. These are the elongated galaxies NGC 3953, and
the barred spiral NGC 4088. They are both about 1/10 of a degree across,
and magnitude 10. See if you can spot them on the way to M109. You can
find M109 nearly 7 degrees north of M 106, and one more degree up, for
a total of nearly 74 degrees above the horizon. M109 is another elongated
galaxy, and is also called NGC 3992. It is the final challenge of the evening,
at nearly magnitude 10, and about 1/7 of a degree across.
Can you manage to see all 10 of this weeks objects?