Artist concept of our Milky Way galaxy

Of the 100 billion stars in our Milky Way galaxy, only a handful have colorful names, while the rest are designated by letters and numbers that are the stellar equivalent of a Social Security card.

The colossal task of naming stars lies with the International Astronomical Union, an organization of professional astronomers that is the only internationally recognized authority for assigning names to celestial bodies. Scientists and space agencies worldwide recognize and use its names.

With a few exceptions of stars whose heritage is rooted in ancient nomenclature, celestial bodies are named with mundane catalogue numbers based on their positions in the sky. These names, like PSR0531+219, may not sound very romantic, but astronomers say it's the only way they can keep track of the stars and find them again. As modern technology enables scientists to detect more stars, the International Astronomical Union updates its catalogue.

"With more stars needing names, astonomers 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," said Dr. Rolf Danner of NASA's Jet Propulsion Laboratory, Pasadena, Calif. Danner is a scientist with NASA's Origins Program, a series of missions to study the formation of galaxies, stars, planets and life. One Origins mission, the Space Interferometry Mission, will pinpoint the location of stars with greater precision than ever before possible.

Long ago, ancient Arabic astronomers named most of the brightest stars, like Algol and Rigel. Greek astronomers named some, like Sirius, while Romans named others, like Regulus.

Stars are also named after the constellation, or area in the sky, where they are found. Astronomers have divided the sky into 88 constellations. The brightest stars in a constellation are named with a Greek letter, starting with alpha for the brightest. For example, the brightest star in the constellation Orion is named Alpha Orionis. Ancient Arabic astronomers called it Betelgeuse.

More information about how stars are named can be found at the International Astronomical Union website at . JPL manages Origins for NASA's Office of Space Science, Washington, D.C. JPL is a division of the California Institute of Technology in Pasadena.

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