Physics Photo of the Week
October
2, 2009
Wobbling Moon
The
gibbous moon was photographed on two separate nights by members of the
Contemporary Astronomy Class. The first frame, where the moon is
less full, was photographed on Monday, Sept. 28 by Marlon Cohn, Dan Faulkner-Bond, and Erin Haggerty. The other
image, when the Moon was more full, was photographed 2 nights later on
Wednesday, Sept. 30 by Peter Calfee,
Garrett Chaffee, and Kesari Fleury. The images were
then aligned, enhanced, and made into an animated sequence.
Notice how the illuminated portion of the Moon that faces the Earth has
grown over the span of 2 nights. This is because the Moon has
advanced in its orbit around the Earth and becomes closer to opposition
from the Sun in the fuller image. Notice also how the craters
show up better when they are closer to the "terminator" - the boundary
between the illuminated and dark portions of the Moon. At the
terminator, the Sun is "rising" on the surface of the Moon, hence the
shadows from the craters are more pronounced. For parts of the
Moon that are well-illuminated, the shadows are not noticeable.
400 years ago, in 1609, Galileo Galilei aimed his primitive telescope
at the Moon and discovered the cratered appearance of the Moon's
surface. Galileo may not have been the first person to have
observed the Moon through a telescope, but he was certainly the first
person to publish his findings in The
Stary Messenger in 1610.
Finally, notice that the animation shows a "wobble" to the Moon and a
slight variation in the size of the Moon between the two
observations. These are due to a small "back and forth" motion
called "Libration" and the variation in the Earth-Moon distance as the
Moon orbits the Earth in an eliptical orbit.
These photos were made with a digital camera attached to a Questar
telescope. This telescope was a recent generous donation to
Warren Wilson College by Ralph Brown.
The two photos that make up the animated photo above are shown
separately below.
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Physics
Photo of the
Week is
published weekly during the academic year on Fridays by the Warren
Wilson College Physics
Department. These photos feature 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:
