October 18, 2005
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Look east late these evenings and you'll see a big, fiery yellow "star" shining much brighter than any other. This is the planet Mars, and it's passing unusually close to Earth during late October and early November 2005. Anyone can see it — no matter how little you know about the stars or how badly light-polluted your sky may be.
During mid- to late October, look for Mars glaring low in the east after 8 p.m. local daylight-saving time. In November, it's there in view as early as 6 p.m. standard time. Later in the evening, Mars climbs higher into better view and shifts over to the southeast. There's nothing else nearly as bright that you can confuse it with.
Mars will be its closest to Earth on the night of October 29–30, passing 43.1 million miles (69.4 million kilometers) from our planet around 11:25 p.m. on the 29th Eastern Daylight Time. However, Mars will look just about as big and brilliant for a couple of weeks before and after that date.
Mars is at opposition (opposite the Sun in our sky) on November 7th. This means it rises at sunset, is up all night, and sets at sunrise.
This is the nearest that Mars has come since its record-breaking close approach in August 2003. At that time it passed by at a distance of only 34.7 million miles (55.8 million kilometers), the closest it had come in nearly 60,000 years. But for amateur telescope users, now is still a very special time. The planet will reach an apparent diameter of 20.2 arcseconds (the angular size of a penny seen at a distance of 620 feet), offering an usually detailed view of its surface. That compares with 25.1 arcseconds in August 2003 (the angular size of a penny at 500 feet), and only 15.9 arcseconds at Mars's next swing-by, in December 2007 (a penny at 800 feet).
In fact, not until the summer of 2018 will Mars again come as close to Earth as it is right now (this statement remains true until mid-November).
Moreover, this year skywatchers at the latitudes of North America and Europe have a big advantage they didn't have in 2003. That year Mars was far south in the sky and never got very high for telescope users at mid-northern latitudes. But this time Mars is farther north and rises higher during the night, affording a sharper, cleaner view in a telescope through Earth's blurry atmosphere.
Good as this fall's showing is, surface details on Mars are always a pretty tough target in a telescope. To begin with, Mars is only about half the size of Earth. Even at its closest, under high magnification it will appear as only a surprisingly small, bright ball with some subtle dark markings, possible white clouds around its edges, and perhaps a tiny remnant of the white South Polar Cap shrunken in the warmth of the Martian summer. The brightest yellow areas are deserts covered by fine, windblown dust. The darker markings are terrain displaying more areas of bare rock or darker sand and dust. Mars rotates every 24½ hours, so you can see it turning in just an hour or two of watching.
To see much detail on Mars, several things all have to be working in your favor. You’ll need at least a moderately large telescope with high-quality optics. (For the lowdown on how to select a telescope wisely, see Sky & Telescope's article "Choosing Your First Telescope".) And you’ll need to wait until Mars rises high in the sky, well above the thick, murky layers of Earth's atmosphere near the horizon. Moreover, the atmospheric "seeing" must be good. This is the astronomer’s term for the constant fuzzing and shimmering of highly magnified telescopic images due to the tiny heat waves that are always rippling through the atmosphere. The seeing changes from night to night and sometimes from moment to moment.
More about Mars and its unusual close approach appears in the September issue of Sky & Telescope and in the November/December 2005 issue of Night Sky, our new bimonthly magazine for beginners.
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