The Half-Astrophysicist Blog

The Full Moon and Mars

Mars is just past opposition…it passed closest to Earth a couple of days ago.  This happens once every couple of years.  The distance between Earth and Mars hasn’t changed much in the last few days, so it is still very well positioned for observing and nice and bright in the sky.

Friday night (January 29th) we have the added bonus of it being very near the full Moon.  This positioning will make Mars very easy to pick out as it is the brightest thing in that part of the sky (other than the Moon, of course!)  Here is a chart I made for 7pm as seen from Tucson.

Mars is bright enough you can see a reddish/orange tint to it, hence the name the Red Planet.

This full Moon is the largest of 2010.  The Moon orbits the Earth in an ellipse, not a circle, so sometimes it is a bit closer to Earth and sometimes a bit farther away.  The Moon is near its closest to Earth (called perigee) tonight so it will appear larger than average.  The apparent size of the Moon is about 14% larger when it is at its closest point to Earth than when it is its furthest (called apogee).

So brave the cold my northern friends…for my southern friends, enjoy a pleasant evening of planet hunting!

Update: I made a small mistake…the Mars is at opposition tonight, January 29th.  I was correct that its closest approach to Earth was a couple days ago on January 27th.  Sometimes closest approach and opposition do not occur on the same day and that one bit me this time!


January 29, 2010 - Posted by | Astronomy, Observing, Solar System

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