Stardate:06:29:98
My Favorite Hunting Ground
If I had to pick an area of the sky as my favorite,
the area of the Lagoon and Trifid nebulas would be the one. It's a wonderful
hunting ground in astronomy. At this time of year, you can find this nebula-rich
area in the southeast sky at around 10 p.m.
Many of the nebulae we will be looking at are
so bright and appear so large across that they're a treat to view with
a pair of binoculars.
At that time of evening, look directly to the
southeast. Now, turn 12 degrees to the south. Remember, a clenched fist
held at arms length is a good estimate of 10 degrees. Look 15 degrees above
the horizon. Here lies a dust-filled nebula, almost visible to the naked
eye under dark skies. Streaking nearly a degree and a half across the sky,
the Lagoon Nebula appears three times wider across than a full moon. In
reality, it's about 60 light years in diameter, and is lit by the ultraviolet
emissions from the hot, young stars within the nebula. It glows pink due
to the combination of red, blue, and purple light emitted from the hydrogen
within. This nebula, also known as MS and NGC 6523, is so easy to find
it's a good first nebula for a beginning amateur astronomer to view.
Less than a degree away from the Lagoon Nebula
is the Trifid Nebula. Also one of the nicest objects in the sky to view,
it can be found just a degree and a half above M8 and one half of a degree
to the east.
This is another dust-rich nebula, and is about
60 percent as bright as M20. Nearly 40 light years across, it occupies
an area nearly 10 times further across than the distance between the sun
and the next nearest star to us, Proxima Centuri. The Trifid Nebula appears,
from Earth, to fill about 1/2 degree side to side.
This is a combination of a reflection nebula,
reflecting light from inside out toward space, and an emission nebula,
emitting light of its own from excited hydrogen gas. Therefore, it appears
pink (emission) and blue (reflection).
Around a half degree away, to the east and slightly
higher above the horizon, lies M21. This is an open cluster of stars nearly
as bright as M8. One quarter of a degree across, it is about 17 degrees
above the horizon and 11 degrees south of southeast.
Now we travel 7 degrees, nearly due east, and
arrive at M25. This is another open cluster.
Four degrees nearly straight up offers up our
next treasure of the evening, the Omega Nebula. Named after the last letter
in the Greek alphabet, it is also called M17 or NGC 6618. This is another
emission nebula, with young hot protostars that can be observed only in
infrared wavelengths. It is nearly as bright as M21, and stretches nearly
three quarters of a degree across the sky. It is just four degrees south
of southeast and 21 degrees above the horizon at 10 p.m.
Next, travel two more degrees above the horizon,
and 1/2 degree to the east. This is the Eagle Nebula, also known as M16
or NGC 6611. This nebula was photographed by the Hubble Space Telescope,
producing the famous image commonly known as the "Pillars of Creation."
In this area entire solar systems are being born. It spans over 1/2 degree
across the night sky and is nearly bright enough to see with the naked
eye from the darkest country skies. It is another dusty nebula, similar
to the first two targets we viewed this week, and looks somewhat like its
namesake.
Finally, travel one and a third degrees further
above the horizon and about one degree to the south. Here we find our last
target of the evening, NGC 6604. This is an open cluster, streaking nearly
two degrees across the sky. About 60 percent as bright M16, it is slightly
more than 24 degrees above the horizon.