Mars is coming!
You've probably heard that line before — no doubt fairly recently, thanks to a bogus e-mail that unfortunately received wide circulation on the Internet this summer with promises of Mars being as big as the full moon.
But this fact is absolutely true: Mars, the only planet whose surface we can see in any detail from the Earth, is now moving toward the best viewing position it will provide to us until the year 2016. Planet watchers have already begun readying their telescopes.
If you haven't seen it, it will be well worth looking for the red planet next week, even though you'll have to wait until after midnight to see it well.
Mars is currently midway between the zodiacal constellations of Taurus, the Bull and Gemini, the Twins and during this week it will rise shortly before 11 p.m. local daylight time. There is certainly no mistaking it once it comes up over the east-northeast horizon. Presently shining like a pumpkin-hued, zero magnitude star, Mars is currently tied for fifth place (with Vega) among the 21 brightest stars.
But as it continues to approach our Earth in the coming weeks and months, Mars will only be getting brighter: it will surpass Sirius, the brightest star in the sky by Dec. 9 and during the latter half of December it will even almost match Jupiter in brilliance.
Late next Wednesday night (or more precisely, early on Thursday morning), Mars will hover about 7-degrees above and to the right of the last quarter moon as they rise above the east-northeast horizon (your clenched fist held at arm's length is roughly 10-degrees in width). As you will see for yourself, the so-called "Red Planet" actually will appear closer to a yellow-orange tint — the same color of a dry desert under a high sun.
Every 26 months, or so, Earth makes a close approach to Mars, as our smaller, swifter orbit "overtakes" Mars around the sun. Because both the orbits of Mars and Earth are mildly elliptical, some close approaches between the two planets are closer than others.
This current apparition of Mars will be nowhere near as spectacular as the oft-referred approach of August 2003 when the planet came closer to Earth than it had in nearly 60,000-years.
Rather, on this upcoming occasion, Mars will come closest to Earth on the evening of Dec. 18 (at around 6:46 p.m. EST).
The planet will then lie 54.8 million miles (88.2 million kilometers) from Earth as measured from center to center. Mars will arrive at opposition to the sun (rising at sunset, setting at sunrise) six days later on Christmas Eve.
That recent Martian e-mail message, which was widely circulated for a fourth consecutive year, lead people to believe, with liberal use of exclamation marks, that on Aug. 27, Mars would appear as bright as (or as large as) that night's full moon in the night sky. The subject header urged viewers to prepare to view "Two Full Moons."
It was amazing (and a little disturbing) to see just how many people actually believed that Mars could loom so large in our sky. But the truth is that even when at its absolute closest possible approach to Earth, Mars can appear no larger than 1/72 as big as the moon; to the unaided eye it would appear as nothing more than an extremely bright, non-twinkling star.
When it comes closest to Earth on December 18th of this year, Mars' apparent disk diameter will be equal to 15.9 arc seconds. To get an idea of just how large this is, wait until darkness falls this week and if you have a telescope, check out Jupiter, gleaming in the southwestern sky; it'll appear about 35 arc seconds across.
In contrast, Mars' disk will appear less than half as big as Jupiter's when the Red Planet comes closest to Earth later this year. While this may sound small, keep in mind that this is still atypically large for Mars. Around the time that Mars is closest, amateurs with telescopes as small as 4 inches and magnifying above 120-power should be able to make out some dusky markings on the small yellow-orange disk, and perhaps the bright white polar cap.
Size isn't everything
From Dec. 15 through Dec. 29, Mars will blaze at magnitude -1.6, a bit brighter than Sirius, but just slightly inferior to Jupiter. Mars will still be positioned between Taurus and Gemini, at a rather high declination of about +27-degrees.
So almost as if to compensate for its relatively small apparent size, Mars will literally soar in the night sky of late-December.
When it reaches its highest point in the sky at around midnight local time, its altitude will be 70-degrees at Seattle, 76-degrees for New York, and an exceptional 83-degrees at Los Angeles. Meanwhile, amateur and professional astronomers stationed in southern Texas and central Florida will see Mars pass directly, or very nearly overhead!