Sky Watch: Pluto's planetary status

"My very energetic mother just served us nine pizzas."

Anyone who's ever studied the solar system in school may have learned this mnemonic device in which each word begins with the same letter as the planets of our solar system in order of their distance from the sun.

Mercury, Venus, Earth, Mars, Jupiter, Saturn, Uranus, Neptune, Pluto.

Pluto? Wait a minute . . . it's not even a planet, is it? Well, we've called it one ever since Clyde Tombaugh found it in 1930, but Pluto is a strange object. It's a world only about 1,400 miles across; if we could bring it to Earth, it would fit inside of Mexico. Its orbit is tipped about 17 degrees to the orbits of all the other planets, and is so elongated that every 240 years it crosses the orbit of Neptune. Pluto is also an icy world with only a few known moons, yet it resides in the realm of the gassy, ringed giants, where dozens of moons exist.

The fact is, Pluto just does not fit the pattern of the major worlds of our system and, because of this, astronomers have reclassified it -- along with four other bodies -- as a "dwarf planet."

While this has irritated more than a few people, it's not an unusual occurrence in science. For example, when people realized that whales showed the characteristics of mammals rather than of fish, they reclassified them as such. No one seems terribly upset about that.

Right now, Pluto lies about as close to Earth as it ever comes -- a "mere" 2.904 billion miles away.But before you get too excited about seeing it, keep in mind a few important facts.

First off, even the largest of telescopes show Pluto as only a tiny pinpoint of light indistinguishable from the thousands of stars behind it. To find it, you must have a very good knowledge of the sky, some excellent star charts, a dark, un-light-polluted sky, a hefty telescope and superb skills at navigating the starry heavens -- especially now, since Pluto appears 200,000 times fainter than the two planets Saturn and Mars in the western sky at dusk and appears against the stars of the constellation Sagittarius, which regular readers may recall lies among the thickest part of the Milky Way.

If you've got all those things -- along with the patience of a saint -- and would like to spend your nights seeking this tiny world, you can find detailed finder charts in monthly magazines such as "Astronomy" and "Sky & Telescope." With Pluto in the sky from dusk until dawn, you'll have plenty of time to carry out the search. And believe me, you'll need it!

When the New Horizons spacecraft -- launched in 2006 -- arrives at Pluto in July of 2015, many of our questions about this icy world will be answered and, just as certainly, many more will be raised.

Whatever Pluto turns out to be we definitely need to learn a new mnemonic device for our solar system's planets.

How about: "My very energetic mother just served us nachos."