A Close Pass With Mars
- Wednesday, August 13, 2003
"The LORD by wisdom hath founded the earth; by understanding hath he established the heavens." - Prov. 3:19
Every seasoned skywatcher knows that the planets are always visible most every night as bright "stars" in the night sky. At various times, we can best see certain planets in the morning before sunrise, and at other times, we can see the planets in the evenings after sunset.
And in general, most of the brighter planets are always easy to find, and behave in a very regular manner. The planets Venus, Jupiter, and Saturn are very conspicuous wherever they are in the night sky. Venus and Jupiter are the brightest objects in the sky, after the sun and moon, and shine steadily at a near constant brightness.
But there is one notable exception: the planet commonly known as Mars. Most of the time, Mars is a faint, indistinct object, hard to find in the sky unless you know exactly where to look. But about every 26 months, Mars brightens nearly 100 times, erupting to a brightness exceeding Jupiter, far surpassing all the other fixed stars. We are currently in a season of such brightness. In fact, for reasons explained below, Mars will be brighter in August 2003 than at any other time in history.
At any brightness, Mars has a distinctly orange color. When it is at its brightest, Mars has a copper color very similar to a shiny, new penny. Modern science has shown that this is due to iron oxide chemical compounds on the surface of Mars, giving it a "rusty" color, the source of Mars's nickname "The Red Planet."
Closest Approach Ever
In classical astronomy, the "inferior planets" are Venus and Mercury, the two planets inside the Earth's orbit, closer to the sun than our world. The "superior planets" are Mars, Jupiter, Saturn and the faint outer planets. The Earth is closest to one of the superior planets at "opposition," when Earth is directly in a line between the planet and the sun. At this time, the planet is "opposite" the sun in the sky, and can be seen rising in the East just as the sun sets in the West.
At opposition, the planet is generally at its closest to the Earth, and is therefore at its brightest. But Mars is the closest of all the superior planets, and so has a very short distance to the Earth during opposition. And Mars is also a very small planet, not very bright when it is at a place in its orbit far from the Earth. Also, Mars has the greatest percentage "spread" of distances from the Earth. Mars is usually around 40 million miles from us at opposition and 235 million miles when at superior conjunction, the opposite side of the sun from Earth. For these reasons, Mars changes dramatically in brightness as it approaches opposition.
Like most of the planets, Mars has a "lopsided" elliptical orbit. Each of the planets has points in their own orbits where they are closest and farthest away from the sun. It so happens that Mars is more lopsided than all of the other classical planets except Mercury. So depending on how Mars and the Earth line up in their orbits, Mars can be brighter at some oppositions than at others.
Planets are closest to the sun at "perihelion," a Greek-derived word that means "next to the Sun." The perihelion of Mars is at a place in its orbit corresponding to "a heliocentric longitude of 336.1 degrees." Without explaining all that, let's just say that Earth passes the point of Mars' perihelion every year on about August 27. However, the planets are all constantly in motion. In any given year, when the Earth passes this point, Mars is likely to be found at some other point in its orbit - except in 2003.
This year Mars will reach opposition on Thursday, August 28, at a place very near the actual point of perihelion. So for this reason, Earth and Mars are extremely close to their theoretical minimum possible distance. As a matter of fact, it has been calculated that Mars and Earth have never been closer at any point in history.
Recently on Resources
Have something to say about this article? Leave your comment via Facebook below!
Listen to Your Favorite Pastors
Add Crosswalk.com content to your siteBrowse available content