Physics Photo of the Week
September
5, 2008
Inside a Galaxy
Of course this is our own galaxy - the Milky Way. It is a
panoramic shot from horizon to horizon from the dark skies of Vermont
on July 6, 2008. Click on the image to view a full-size
image. The most conspicuous
feature is the dark center lane
caused by interstellar dust. Compare the above picture of
our own galaxy with a similar, but very distant galaxy: NGC891 pictured
at right and also featured in Physics Photo of the Week for Nov.
11, 2005.
Notice that the right-hand (southern) end of the Milky Photo is
brighter than the rest. This is looking through the constellation
Sagittarius toward the center of our galaxy. There is a central
bulge in our galaxy's center as in the external galaxy, but the dust
obscures the center from our view. Radio astronomy easily
penetrates the dust and detects the center of our galaxy - one of the
first discoveries made with radio telescopes in the late 1940's.
To our eyes - even at dark sky sites - the Milky Way is not nearly as
bright as shown in the photograph. The brightness is enhanced by
using time exposures. In each section of the photo, the camera
took a couple of 30 second exposures. The two exposures were
aligned and "stacked" to minimize the random noise. The three
sections were then "stitched" together to make a composite panoramic
image. Finally the contrast was enhanced to make the faint
features more visible. The colors are true, however. The
milky way clouds are truly red toward the center (like a "strawberry
milkshake"! The redness actually arises from hydrogen emission in
the many distant clouds of the galaxy. The bright star-like
object at lower right is the planet Jupiter.
The Milky Way was also featured on Physics Photo of the Week one year
ago (Sept.
7, 2007). The image of a year ago shows Jupiter clearly in a
different place among the constellations.
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.
All photos and discussions are copyright by Donald
Collins or by the person credited for the photo and/or
discussion. These photos and discussions may be used for private
individual use or educational use. Any commercial use without
written permission of the photoprovider is forbidden.
Click
here to see the Physics Photo
of
the Week Archive.
Observers are invited to submit
digital photos to:
