28 January 2010

Mars and the Biggest Full Moon of 2010

The next few days offer a chance to see Mars and the full Moon together while each celestial body passes through its closest point to the Earth in their orbit. When Mars and Earth line up in their orbits around the Sun, we call that "opposition" and it represents the closest approach between the two planets. This takes place approximately every two years and when it does, Mars appears brighter than usual and is larger in a telescope. Also at opposition, Mars rises just as the Sun sets and is up all night. Mars is at opposition on Friday January 29th.

The Moon has an elliptical orbit around the Earth and as such, each orbital period (approximately 29 days) it is a bit closer to Earth (called Perigee) and then a bit farther from Earth (called Apogee) This month, the Moon is full and is at Perigee on the same date, Friday January 29th. It is also next to Mars so when you look outside on Friday evening, you'll be seeing a nice lineup of a couple of our nearest neighbors. When the Moon is at Perigee, it is a considerably bigger object in the sky than usual. The website Spaceweather.com highlights this nicely in their article.

I have written about the biggest full moon of the year in a previous blog post, if you want to get more information about that subject.

Regarding Mars and opposition, there was a great deal of hype in August 2003 when Mars had a particularly close opposition and was inaccurately stated as "being as big as the Full Moon." That won't ever happen, of course, but it certainly inspired a lot of people to take a look at Mars that summer. This week Mars will be less bright and big compared to 2003 but still a worthy binocular or telescope target. The next close encounter that will rival the 2003 lineup will be in 2018. For an extremely detailed chart and description of the Mars opposition phenomenon, visit the seds.org site.

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