Physics Photo of the Week

October 31, 2014

Partial Solar Eclipse
In October the Sun-Earth-Moon system offered two eclipses.  There was a total Lunar eclipse on October 8 in which the Moon passed through Earth's shadow.  Unfortunately, that event was clouded out at Warren Wilson College.  About two weeks later, as the Moon swung around the other side of the Earth, it passed between the Earth and the Sun and partially blocked out the Sun to produce a partial Solar eclipse that was visible from the Blue Ridge Parkway on October 23 during Fall Break.  In the telephoto image of the Sun at left, we see the Sun with a piece "cut-out".  The cut-out part is a silhouette of the Moon.  The Moon appears black because the very intense Sun is on the far side of the Moon, and there is very little light bouncing from the Earth to light up the Moon. 
The photograph was taken through a small telescope that was equipped with a very dark special solar filter.  NEVER LOOK AT THE SUN - ESPECIALLY THROUGH A TELESCOPE - WITHOUT THE SPECIAL FILTER!

We also see a very large sunspot group near the center of the Sun's image.  The largest sunspot in this group is larger than the diameter of Jupiter, about 10 times the diameter of the Earth.  More about Sunspots in a later Physics Photo.  Click on the image above to see a larger image.

This eclipse began about 45 minutes before sunset.  The weather here was very clear all day, but a bank of clouds appeared in the west and blocked out the Sun before the Moon got half way across and before the Sun set below the horizon.  The animation at right shows the progress until the clouds rolled in.  The Moon slowly advances across the face of the Sun during the 20 minutes of visibility.

Even though the Moon is smaller than the Earth, the Moon is so close to us that occasionally the Moon crosses the center of the Sun and completely blocks out the Sun giving several minutes of near darkness in the middle of the day.  Such an event is a total solar eclipse - a very rare event at any given point on the Earth.  On August 21, 2017, a total solar eclipse will pass coast-to-coast along a narrow path through the United States coming through parts of Western North Carolina - very close to Warren Wilson College.   Click here to see a map.   I will probably travel to Nebraska to view that eclipse where the weather is much more likely to be favorable.  I strongly urge readers of this page to make a serious effort to travel to see a total solar eclipse in their lifetimes.  It is truly a remarkable experience when the Sun is totally blocked out and the only light comes from the delicate corona that is invisible in the bright Sun because it is millions of times less bright.

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

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.

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