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NIGHT SKIES

Looking northeast on August 12 at 4:00 a.m. with the Perseid radiant point shown

Looking northeast on August 12 at 4:00 a.m. with the Perseid radiant point shown.

Night Sky August 2005—When Mars attacks!

Charlie Christmann

Mars will never be closer to Earth than it will be in August. The Red Planet will look as big as the full moon. Little Green Men are invading the Earth. Okay, maybe I did make up the last one, but I'm sure you have seen these and other similar proclamations on the Internet, in your in-box, and even by mistake in the Signpost last month. And, like so many other things that come via the Internet, it is not the full truth. This blather was dredged up by someone using old information from 2003 and making it appear to be a 2005 spectacle. Here is the real story:

In August 2003, Mars was a spectacular sight. According to NASA, on August 27, 2003, Earth and Mars were the closest they have been for about sixty thousand years. In fact, this meeting between the Earth and Mars was so well hyped in 2003 that a NASA article sought to explain the event. In that article, NASA stated, “Much has been made of the fact that the August 27th encounter with Mars is the closest in some 60,000 years. Neanderthals were the last to observe Mars so favorably placed. This is true. It's also a bit of hype. Mars and Earth have been almost this close many times in recent history.”
science.nasa.gov/headlines/y2003/18jun_approachingmars.htm

So, why do Mars and Earth come closer together some times and not so close at others? It has to do with the slightly elliptical orbits that both the Earth and Mars follow. Mars's orbit is a bit more oblong than ours, ranging from 128.39 million miles from the Sun at perihelion (closest to the Sun) to 154.9 million miles at aphelion (furthest from the Sun). Compare that to Earth's orbit that varies between 91.4 million miles to 94.5 million miles. This means that the closest the two planets could possibly be is 33.9 million miles apart. Because Mars takes 687 days to orbit the sun, Earth does not pass Mars at the same point in its orbit each year. By a quirk of the orbits closely aligning in 2003, we came within 34.8 million miles, close to the minimum possible distance.

Mars oppositions (the closest approach by Earth) happen about every twenty-six months. Every fifteen or seventeen years, opposition occurs within a few weeks of Mars' perihelion. This means that we will have close encounters with Mars every fifteen or seventeen years.

In 2005, Mars is not as close to its perihelion as we pass by. On August 31, Mars and Earth will slide past each other at a distance of forty-three million miles. That is close enough for you to enjoy watching Mars swell and brighten during the course of the month. Amateur astronomers with backyard telescopes will be able to spot polar ice caps and dust storms and strange dark markings on the planet. Even the least-attentive stargazers will be asking you about that bright red thing in the sky.

So, the claim that "no one alive today will ever see this again!" is a little misleading. While it is true that the next time Mars will be as close to Earth as it was in 2003 will be on August 28, 2287, there will be plenty of other close approaches similar to this year's event. Our children and our children's children are not likely to miss out altogether. And, who knows, by 2287 some of our future relatives may be observing the close encounter from the Martian perspective.

    It's Raining Perseids

This year's edition of the Perseid meteor shower is in full swing. The shower performs this year from July 17 to August 24 and is predicted to peak in the early morning hours of August 12. Expect to see about a hundred shooting stars per hour during the peak.

Perseid meteors come from Comet Swift-Tuttle. Every 130 years, the comet swoops in from deep space (beyond Pluto) and plunges through the plane of the solar system not far from Earth's orbit. Astronomers once worried that Swift-Tuttle might hit our planet, but recent calculations show otherwise. There's no danger of a collision for at least a millennium, and probably never.

The comet's orbit is littered with bits of dusty debris, and little bits of Swift-Tuttle do hit Earth. These dusty grains boil away from the comet's icy nucleus as Swift-Tuttle nears the Sun. We plow through that dust cloud once a year beginning in late July.

Perseid dust particles are tiny, most no bigger than grains of sand. Yet they hit our atmosphere at about 132,000 mph. Even a tiny dust speck can become a brilliant meteor when it hits the atmosphere at that speed. But don't worry about being struck by one of these. The fragile grains disintegrate long before they reach the ground.

The best time to look for meteors is when Perseus is highest in the sky—between 2:00 a.m. and dawn. On August 12, set your alarm for two o'clock in the morning. Go outside; lie down on a sleeping bag or a reclining lawn chair with your toes pointed northeast; and gaze upward. Soon you'll see shooting stars racing along the Milky Way. Repeat the procedure on August 13. The shower's peak is long-lasting, and you're likely to see plenty of meteors on both days.

    The Moon and Planets

  • Mercury slips below the horizon by the first of August, but will reemerge as a morning star by mid-month. Mercury reaches its highest point in the morning sky on August 23.
  • Venus hovers low in the west at sunset this month. Look for the Moon hovering close to Venus on August 8.
  • Mars is a late-night planet. Look for it rising after midnight. It should be high in the northeast around dawn. Look for the Moon and Mars together on August 25.
  • Jupiter gets closer to the western horizon at sunset as the month progresses. The Moon and Jupiter make a close pair on August 10. Jupiter joins Venus low in the evening sky late in the month.
  • Saturn has rounded the Sun and will become an early-morning star by mid-month.
  • This month's full moon is called the Full Sturgeon Moon because fish in the Great Lakes seem to be an easy catch. Indian tribes called this month's moon the Green Corn Moon or the Grain Moon. The full moon occurs on August 19 and the new moon occurs on August 4.

If you have questions, comments, or suggestions, you can e-mail me at sandovaldarksky@yahoo.com.

Starry night at Coronado Monument

On August 13, from 7:00 to 10:00 p.m., view the night sky and learn about the planets, stars, and galaxies. Children can create an astronomy craft to take home. Bring your telescope or view the skies through those provided. Listen and talk to an astronomer. All ages are welcome, and admission is free. Coronado State Monument, 1-25 Exit 242, two miles west on Highway 550, Bernalillo. For further information, call 867-5351.

 

 

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