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Moon and Mars

November 26, 2013

After spending the last couple of months cruising past the celestial lion, the planet Mars has crossed into the adjoining constellation Virgo. Yet the closest bright star is the lion’s tail, Denebola. They’re high in the southeast at first light tomorrow, with Mars close to the upper left of the Moon and Denebola farther along the same line.

Leo, the lion, is one of 88 official constellations. Each has its own precisely defined borders. Those borders make most of the constellations look like pieces of a jigsaw puzzle, with lots of interlocking tabs.

The main body of Leo, for example, is roughly rectangular. But the constellation has a big tab at its northwestern corner, and another at its southeastern corner. In all, the lion’s outline consists of 16 separate facets.

Mars just passed through the southeastern tab and has crossed into Virgo. The Moon is just inside the tab when it’s visible before dawn tomorrow, although it’ll also move into Virgo during the day.

Mars will remain inside Virgo’s borders until next August. It’ll hang around for so long because the viewing angle between Earth and Mars is changing as the planet gets ready to pass opposite the Sun in our sky. In about three months, it’ll stop its normal eastward motion as seen from Earth and appear to stand still for a while. Then it’ll move backwards for almost three months before once again changing directions and resuming its normal course — finally leaving Virgo behind.


Script by Damond Benningfield, Copyright 2013

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