Physics Photo of the Week
April
27, 2007
Galaxy M51
Messier 51, the
Whirlpool Galaxy, a favorite among amateur astronomers, is currently
situated very high in the evening sky in the constellation Canes
Venatici near the end of the handle of the Big Dipper.
This is the second color image published that is produced with the new
CCD camera that
the Physics Department has acquired with the help of the Small Projects
Grant of the American Astronomical Association. (The earlier color
image consists of the Great Nebula in Orion published on Feb.
23, 2007) The color image
was produced by photographing through three separate filters - red,
green, and blue. The three colors are then combined in a computer
using the appropriate colored dots for the corresponding images.
The image was taken on April 22, 2007 on Warren Wilson Campus using a
Celestron 8-inch telescope donated by Bernard Arghierre. The
imaging session lasted about 1 hour in which several 2-minute exposures
were made in each color. The images of each color were aligned
and co-added to minimize the noise before combining the different
colors.
This galaxy is believed to be between 31 - 37 million light years
distant - way beyond the outskirts of our home Milky Way galaxy and
considerably further than our nearest spiral neighbor - the Great
Galaxy (M31) in Andromeda (see PPOW
for November 17, 2006). The Whirlpool Galaxy has a close
neighbor - a smaller galaxy known as
NGC 5195 near the top of the photo. It is believed that these two
galaxies collided in the "recent" past - about 100 million years
ago.
Notice how one of the spiral arms of M51 appears to be stretched until
it merges with the smaller galaxy. The spiral arms in galaxies
such as the Whirlpool Galaxy are made prominent and visible by the
existence of young stars in the spirals. The spirals are believed
to be shock fronts of compressed interstellar matter - dust and
hydrogen gas. The compression wave initiates the gravitational
condensation of clouds into clusters of stars. Young stars
clusters are characterized by hot, blue stars, thus making the spiral
arms visible. Compare the color of the spirals with the reddish
hues of the neighboring galaxy - which consists of old cool
stars. Galaxies such as this consist of about 100 billion (1011)
stars. The other star-like objects in the photo are foreground
stars relative close by in our own Milky Way.
Much of the astronomical observations currently conducted with the CCD
camera consist of measuring the light output from cataclysmic variable
stars. Watch this page for more news.
Physics
Photo of the
Week is
published weekly during the academic year on Fridays by the Warren
Wilson College Physics
Department. These photos feature an interesting phenomena in
the world around us. Students, faculty, and others are invited to
submit digital (or film) photographs for publication and
explanation. Atmospheric phenomena are especially welcome.
Please send any photos to dcollins@warren-wilson.edu.
Click
here to see the Physics Photo
of
the Week Archive.
Observers are invited to submit
digital photos to:
