Mars

When and where is Mars in the sky this summer?

As I type this in mid-July, Mars is a very late-night object, glowing brightly as it rises in the southeast around 11PM.

But to get a clear look at it -- or any planet -- through a telescope, it must be higher in the sky, so as to look through less of our turbulent atmosphere. This happens several hours after it rises, and shifts about 30 minutes earlier per week as Earth overtakes Mars:

about 1:30AM in mid-July;
12:30AM by early August;
11:30PM by mid-August;
10:45PM by the opposition on August 27th; and
9:30PM by mid-September.

(These are approximate times when Mars reaches 25 degrees above the horizon, in the southeast, in Illinois; it reaches its highest, in the south, a couple of hours later, so waiting a bit longer may help. But you should be able to get a good telescopic look by the times given here.)

I don't have a telescope -- how can I see Mars with one in the Champaign-Urbana area?

Two local groups -- the Champaign-Urbana Astronomical Society (CUAS) and University of Illinois Astronomical Society (UIAS) -- will offer free public Mars viewing this summer, weather permitting:

CUAS : Wednesday Aug 27th, 10PM-midnight, at Meadowbrook Park in Urbana
UIAS : Friday Aug 29th, 9PM onward, at U of I observatory
CUAS : Saturday Aug 30th, at CUAS observatory, south along 700E from the Monticello Road
UIAS : Friday Sep 5th, 9PM onward, at U of I observatory
CUAS : Saturday Sep 6th in soccer fields just east of Parkland College
UIAS : Saturday Sep 13th, 9PM onward, at U of I observatory

In case of clouds, don't come, we won't be there!

For further information (and possibly other dates) see the clubs' web sites:
CUAS: http://www.prairienet.org/cuas/ or call Dave Leake of Staerkel Planetarium at 351-2567;
UIAS: http://www.astro.uiuc.edu/~uias/

What if I'm not near Champaign-Urbana?

See this worldwide list of Mars 2003 events.

What's happening with Mars this summer?

What's an "opposition" anyway?

Earth overtakes Mars in its orbit -- we see it at opposition, 180 degrees away from the sun -- about every 26 months. Mars is then at its closest (for that year) and brightest; it rises near sunset and sets near sunrise.

It remains pretty close, and pretty bright, for a month or two before and after each opposition. Then Earth races on, leaving Mars far behind, until the next opposition two years later.

Some oppositions occur when Mars is near the closest point (in its elliptical orbit) to the sun; we see these about every 15 or 17 years, for example in 1971, 1988, 2003, and 2018. These are much closer (by tens of percent) than other oppositions, and we get our best views of Mars in these years.

[Diagram of recent oppositions of Mars, showing Earth-Mars distances]

How special is this year's opposition of Mars?

This year's opposition is closer than most close ones, but only by a tiny bit. The 2003 opposition is about

3% closer than the next close one in 2018,
5% closer than the last close one in 1988,
0.8% closer than the previous one in 1971.

In other words, not much. So don't get too excited by the stories about Mars coming closer than in 50,000 years or whatever. It's true, but only by a hair.

In contrast, this year's is about

20% closer than the last not-so-close opposition in 2001 and
25% closer than the next one in 2005, and something like
45% closer than the least-close recent opposition in 1995.

In summary... Mars is a very pretty planet, and we should get a good look at it this year -- one that won't be nearly equalled for 15 years. That is a good reason to look at Mars this summer!

August, 2003 vs November, 2005

Proximity isn't the only thing that lets us get a good look at Mars. A disadvantage of the 2003 apparition, for us in northern temperate latitudes, is that Mars is pretty far south -- it never rises higher than about 35 degrees above our horizon in central Illinois. That means we see it through almost twice as much air as if it were very high in the sky -- and more air means more chance of atmospheric turbulence (bad seeing) interfering with the view. (Of course, if we lived in say Australia, Mars' 2003 position would be no disadvantage -- Mars passes nearly overhead there!)

Although Mars won't be so close to Earth at its next opposition in early November, 2005, it will be much higher in the sky for northern temperate observers. The better seeing at that high altitude may well make up for the increased distance.

So, try to remember what you see this time and compare it with what's visible in a couple of years! The 2005 apparition will also be in a prettier part of the sky, not far from the Pleiades.

What if I don't get to see Mars on August 27th?

Have I missed my lifetime's chance?

This year, Mars is at opposition on August 27th/28th, and it will be closest to Earth around that date.

But the distance varies only slowly then; it's

within 5% of its best for about a month (Aug 11 - Sep 12), and
within 20% of its best for about two months (July 24 - Sep 29).

So catch it when you can, but don't worry about exact dates.

[diagram of Earth overtaking Mars from July-October 2003]

Here's a one-page printable (PDF) version of the above material.

-- Stuart Levy, U of I Astronomical Society & Champaign-Urbana Astronomical Society, 2003 July 20; times of observing sessions added August 20