Physics Photo of the Week

February 16, 2007

Mercury and Venus
The planet Mercury has been visible the past 1-1/2 weeks very low in the western sky soon after sunset.  Mercury is the red object just at the tips of the trees at the horizon.  Venus is the much brighter object at upper left.  The small speck to the right of Venus is an artifact - presumably internal reflections on the camera lens.

If the weather is clear you may see Mercury - the closest planet to the Sun - but you need to look no later than 7:00 pm.  You need a clear view of the western horizon - unobstructed by mountains and trees.  Mercury is also very red as the photograph indicates, and is actually quite bright.  It is not as bright as Venus, but it is brighter than many "bright" stars.

The photograph was taken on February 10, 2007 at about
7:00 pm.  12 exposures were made lasting about 5 seconds each.  The images were then co-added - lining up the planets in each image.  Because celestial objects appear to move across the sky, the trees appear streaked in the co-added images.  Otherwise the celestial objects would appear streaked.  The image at the right shows a straight sum with no alignment.  The planets (and stars if visible) appear streaked due to the apparent movement of the sky.

If you miss seeing Mercury during this apparation, it will soon be visible in the east morning before sunrise in early March, but it will be much lower in the sky.  The next evening appearance of Mercury will be late May - early June, 2007.  Mercury appears frequently, but remains visible only for short durations due to its short orbital period about the Sun (88 days).  Venus will be highly visible all through the spring of 2007 and reach it's peak brightness in late June, 2007 just after Mercury rejoins Venus in the evening sky.  Enjoy the skies!

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

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

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