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Black is back: Dark skies show off Mars

Posted: Sunday, August 10, 2003

Now that summer makes way for some more nighttime hours, hopefully cloudless, I'm able to resume my astronomy column.

Don't misunderstand me. I love Alaska, but I love the winters, too.

The astronomy season starts out with a bang as the first major planet will be Mars at its best. It'll be joined by Saturn, Venus and Jupiter later this year, and there will be a lunar eclipse Nov. 9, but for now it's Mars.

The red planet has been an odd-year planet throughout the 1990s and 2000s. For example, it became last prominent in 2001, then now, and next time in late 2005. Mars needs about one year and 11 months for one orbit. So as Earth orbits the sun and is back at the same spot after exactly one year, Mars is almost on the other side of the sun.

As we're trying to catch up during our second orbit, Mars makes a feeble attempt to elude us, but finally we've caught up and get closest to Mars once again after two years and two months, a little longer than one Mars orbit. Hence the two-year recurrence of Mars from our vantage point.

As for late 2003 and early 2004, Mars has been moving and retrograding across Aquarius from June (the retrograde motion started in early August) through November (retrograde until late September), Pisces in December and January, Aries in February and Taurus in March and April. As Mars will enter Gemini in May of next year, Earth and Mars will be in disparate parts of their orbits.

We like to be close to Mars to observe it because we can only see it when both of us are on the same side of the sun, otherwise the sun would be in between, rendering Mars obliterated by the bright daytime skies, as will be the case for the remainder of 2004.

But we also like to be closer to a planet because it appears brighter and bigger, which is especially the case for Mars. And this year is extra special because two events coincide: Mars closest approach to the sun (called perihelion) on its elliptical orbit on Aug. 30 and Mars being in opposition with respect to Earth the sun on one side from us, Mars on the other on Aug. 28, making it, at 35 million miles, our closest encounter in recorded history, in fact, since our Neanderthal cousins saw it in 57,617 B.C. even closer.

Although that's a record and there'll be some media hype about it, the main event is to enjoy observing Mars. In other words, don't wait until Aug. 28, 2287, when it'll be still closer, brighter and bigger, but enjoy it now, in two years, in four, in six. (See the June 2003 issues of Sky and Telescope and August 2003 of Astronomy, available at several libraries and stores on the Kenai.)

You can't miss reddish Mars because it'll be the brightest object in the nighttime sky, apart from the moon, if that is out.

The diagram shows the positions of Mars during August and September around midnight. View Mars due south about 15 degrees above the horizon, either above the Kenai Mountains on the south side of Kachemak Bay or above Cook Inlet. Its retrograde motion (left to right, or east to west) can be noticed when Mars positioned relative to the stars in Aquarius, is recorded for a few weeks.

I will take pictures of this area of the sky weekly with my students in my Kenai Peninsula College astronomy class this fall, so send me an e-mail if you like to have those photos shared.

There are some bright stars out, but none of them is nearly as bright as Mars, though they could be more prominent if Mars is lost in some haze on the horizon. These stars are reddish Arcturus and Antares in the west and southwest (these are huge, though cool radiating at around 5,000 F which corresponds to red dying stars called Red Giants, unlike Mars, which gets its color from its oxidized, rusted surface rocks), while Mars is in the east or south, depending on the time of night. Other bright stars make up the summer triangle overhead, Vega, Deneb and Altair.

I just don't have the space here to rattle off facts about Mars, but you can look up a lot about Mars in plenty of good books on the solar system (there are good juvenile books, too). However, if you own a telescope or if you would like to join me some evening, you will see a reddish, yet small disk (it's still tiny in most amateur telescopes, so don't expect too much) and with some patience you might see a polar cap or two and contrast bright and dark regions on Mars' surface (see Astronomy August 2003, page 82).

Interesting dates also are Tuesday and Sept. 8 when Mars and the moon will appear close to each other, and Sept. 24 when Mars is closest to Uranus.

Binoculars are advised to find Uranus. Aquarius doesn't have any bright stars, but Mars helps. See if you can recognize the faint stars that make up Aquarius. Then use binoculars to go from Mars to the star Iota Aquarii on its upper right. Now you should have in your binoculars the same view as depicted in the inset. Use Iota and the triangle 39, 42 and 45 as a recognizable pattern. There will be two objects of similar brightness above the triangle: the star e Aqu and the planet Uranus. Come back a week later and you'll notice Uranus will have retrograded to the right.

And since I mentioned the word retrograde a few times: Mars, Earth and all other planets orbit the sun counter-clockwise, each at its own fairly steady rate, always in the same direction. But as we're speeding past Mars and other outer planets, it looks or appears as if Mars is going backward (retrograde), but only because we're changing our vantage point in space so rapidly.

Andy Veh is the physics and astronomy instructor at Kenai Peninsula College. This column appears on the first Sunday of each month. He can be reached at aveh@uaa.alaska.edu.



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