Mars joins Santa in the sky Christmas Eve
The Red Planet won't appear this big and bright again until 2016.
December 18, 2007
Christmas Eve will bring a lot more than Santa this year. Mars shines brightest and remains visible all night when it reaches opposition December 24. That night, the Red Planet shines brighter than any star; only the Full Moon and Venus will outshine it. An opposition occurs when Mars lies opposite from the Sun, becoming fully illuminated. Mars' oppositions happen roughly every 780 days.
Mars won't be this big or bright again until 2016. No equipment - just warm clothes - will be needed to enjoy this spectacle.
The Full Moon helps observers find Mars. On December 23, the Moon sits just 1° from the planet (one degree is equal to 2 Moon-diameters). Observers can also track Mars' westward motion against the stars of Gemini.
"Use binoculars, and about every other night, see which stars lie close to Mars," says Astronomy magazine Senior Editor Michael Bakich. "By doing this, observers can learn about planetary motion."
Even under urban skies with heavy light pollution, it will be easy to see martian details with a small telescope.
Mars' closest point to Earth came December 18, when it laid 54.8 million miles away. Opposition and closest approach don't coincide because Mars has a noticeably elliptical orbit.
Mars will look almost as bright several weeks before and after December 24. Let Santa be the only one to worry if Christmas Eve presents a cloudy sky.
Make a note
Mars varies in angular measurement from 13.8" to 25.1". Angular measurement is used to describe how large a celestial object is. Mars' brightness varies from -1.5 to -2.9 magnitude.
A day on Mars is 37.4 minutes longer than a day on Earth. So, if you're observing Mars at the same time every night, its markings will appear to move 9.11° to the west each day.
Mars' declination will measure 26° 46' December 24th. Altitude is important. The less air Mars is viewed through, the better. So, if it's possible, head south to view the opposition.
For tips on viewing the opposition, read Bakich's "15 tips for observing Mars," in the December 2007 issue of Astronomy magazine.