Physics Photo of the Week
famous Horsehead Nebula is a popular deep sky object found in the
constellation Orion. The dark shape of a horse sillouette is a
cloud of dust and gas in interstellar space. The area of Orion,
high in the southern sky in February, contains many such dust clouds -
all part of the Milky Way. A monochrome image of the Horsehead
was featured a year ago (Feb.
2, 2007) where much of the physics of the nebula was
This image was produced in the Contemporary Astronomy class at Warren
Wilson College on Jan. 30, 2008 by students Kat Coker, Suzanne Lutsky, Daniel McKinny,
Anne Liffiton, and Raya Cooper assisted by physics professor
Donald Collins. The photograph
involved many exposures for 30 seconds each through red, green, and
filters. The images through each filter were co-added or
"stacked" to increase
the image viability. Finally the different colors are combined to
give a final color
result. The telescope is an 8-inch diameter Schmidt-Cassegrain
telescope and a SBIG CCD camera.
Notice that many more stars are visible on the right side of the photo
than on the left. The dark cloud blocks many of the background
stars on the left side. The visible stars on the left are
probably foreground stars in front of the cloud. The red color of
the background is real. There is a bright star (Sigma Orionis)
off the right side of the picture that is very hot and emitting
invisible ultraviolet radiation.
The UV radiation impinges on clouds of hydrogen and cause the hydrogen
to glow or "fluoresce" - emitting visible light of lower energy due to
the partucular energy levels of atomic hydrogen.
The location of the Horsehead Nebula is indicated by the cross-hairs in
the image of Orion at right. Notice that one cannot see any of
the horsehead formation in the image. The star Sigma Orionis that
causes the clouds to glow is located in the upper right quadrant of the
Photo of the
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 firstname.lastname@example.org.
here to see the Physics Photo
the Week Archive.
Observers are invited to submit
digital photos to: