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: