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Naming the stars

Before telescopes, if was pretty easy. Now who decides?

When United States astronaut James Lovell orbited the moon in his Apollo 8 spacecraft with Frank Borman and Bill Anders in December1968, he picked out a mountain in the Sea of Tranquility and named it after his wife, Marilyn. "We were the first people to see that mountain," Captain Lovell explains, "and we figured we had as much right as anybody to give it a name."

Anyone can pick out a feature on the moon, or a star, or a nebula and give it a name. You could pick out a star and name it Mortimer Trendelbotham if you wanted to. But if you went to an observatory and asked an astronomer to point his telescope at Mortimer Trendelbotham, you wouldn't get very far, because no one else has agreed to give that star that name.

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Stars and constellations were first given names thousands of years ago. Someone imagined that a certain cluster of stars looked like a lion. They called it Leo and told stories about it. They named some of its stars. The stories and names spread until many people used them.

But the names depended on the region. Astronomers in Arabia would give a star a name. In Greece, it had another name. In China or Africa, the names and constellations were different.

Some names stuck, though, even across borders. In many parts of the world today, some stars still can be identified by ancient names. Betelgeuse (BEE-tel-jewss) and Rigel (RY-jel) are Arabic names. Sirius (SEER-ee-us) is Greek. Regulus (REG-yew-luhss) is Roman. People all over the world have their own regional names for the stars. But to astronomers, only about 100 stars have names like these.

As astronomers observed the thousands of stars they could see in the sky, they realized they needed a system for naming them all. In 1603, German astronomer Johann Bayer developed a system that was adopted by many other scientists of his time. He gave a Greek letter to each star in a constellation, starting with the brightest.

Alpha is the first letter of the Greek alphabet, so the brightest star in the constellation Centaurus (sen-TAR-us) was named Alpha Centauri. The second brightest is Beta Centauri, and so on. After using up the 24 letters of the Greek alphabet, he used Roman letters, first in lower case (a, b, c), then in upper case (A, B, C). But this system was still limited by the number of letters.

In 1725, British astronomer John Flamsteed published a star catalog with a new system. He numbered all the stars in each constellation, from west to east. Vega, in the constellation Lyra, is known in the Bayer system as Alpha Lyrae. In the Flamsteed system, it is 3 Lyrae.

But as telescopes came into common use, thousands more stars could be seen. These stars had to be cataloged by newer systems. Most of these systems use numbers that help identify where the star is in the sky. Today, stars are commonly identified by a combination of systems. Stars like Antares (an-TAR-eez) or Polaris (po-LAIR-uss) are often called by their ancient names. They have other names, too.

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Now that billions of stars are visible through powerful telescopes, star identification numbers are getting pretty long. "With more stars needing names," says Rolf Danner of NASA's Jet Propulsion Laboratory in Pasadena, Calif., "astronomers have been running out of numbers, so it has been necessary to add digits, just as phone companies add new area codes as the population grows." This results in star names like PSR0531+219.

Telescopes also helped observers realize that some stars aren't stars at all. They're galaxies (huge groupings of stars) or nebulae (giant, glowing clouds of dust or gas) or quasars (odd, starlike objects). Some of these quickly got names based on their appearance, such as the Crab Nebula, Horsehead Nebula, or Ant Nebula.

French astronomer Charles Messier (MESS-ee-yay) began a catalog of nebulae and galaxies in 1774 with 45 objects. Others were added until now there are 110 Messier objects, some of the most impressive deep-sky objects visible from the Northern Hemisphere. In this system, the Crab Nebula is "M1."

Another common system published in the late 19th century is the New General Catalog. In this system, the Crab Nebula is NGC1952.

Finally, in 1919, the International Astronomical Union was founded. One of its purposes is to regulate the naming of celestial objects. Sixty-six countries have agreed to let the IAU be the official organization for approving and recording names. The IAU has set specific guidelines for naming new objects and for listing them in catalogs and articles.

Before the IAU, craters, plains, and mountains on the moon could be named by anyone who spotted them. Now there is an official procedure. There are also themes for naming features on a moon or planet. Moon craters are named for philosophers or scientists. Plains are called "seas" (mare in Latin), because early observers thought they were bodies of water.

As spacecraft began traveling through the solar system, more moons and asteroids were discovered and more features of the planets were seen.

More naming conventions were established. Many of the features of Venus (the name of a mythological goddess) are given feminine names, for example. Most new moons continue to receive names from Greek and Roman myths. (Proteus, a moon found orbiting Neptune in 1989, was named for one of Neptune's sons. Uranus's moons, however, are named after characters from Shakespeare and Pope.)

When someone discovers a new object or feature, he or she must now submit an application to the IAU with a proposed name. If the name is approved, it can then be included in maps and catalogs.

The IAU wouldn't accept Jim Lovell's name for Mt. Marilyn. "It didn't fit their theme for naming moon mountains after 14th-century people," Lovell says.

But Apollo 11 astronauts used Mt. Marilyn, by that name, as a guide when they landed on the moon in 1969. And when you're one of the few human beings who have ever seen the mountains of the moon up close, you've earned the right to call them anything you want.

(c) Copyright 2001. The Christian Science Publishing Society

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