Physics Photo of the Week

September 17, 2010

The planet Mercury is a challenge to see, but is now visible in the pre-dawn eastern sky.  You have to get up and be looking near the eastern horizon by 6:00 am.

Mercury is the visible as a "star" in the lower center of the image.  The bright star Regulus in Leo is visible in the upper center.  If it weren't for the twilight glow Mercury would be appear brighter than Regulus - a "major" star.  Because of Mercury's closeness to the Sun as the innermost planet, it never appears very far from the Sun in the sky - thus it is always immersed in the twilight glow of the Sun, and often obscured by lo-altitude haze and clouds.  As a result Mercury is quite difficult to see. 

Mercury will next be visible in the early evening after sunset in late November-Early December.  The Warren Wilson campus has many locations where the western horizon is noticeable (Dogwood Ridge, Spidel for example), but the Sun will set very early (around 5:10 pm in Western North Carolina) making the optimal times to view Mercury between 6:00 and 6:30 pm. 

Check out a previous image of Mercury on Physics Photo of the Week published on February 16, 2007.
The colors may appear a bit over-saturated in this photo.  That is because of extensive contrast enhancements in order to make Mercury and Regulus visible on the computer screen.

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.

Click here to see the Physics Photo of the Week Archive.

Observers are invited to submit digital photos to: