In recognition of the 50th anniversary of the start of the Space Age, an asteroid has been named "Astronautica." Minor planet number 100,000 (also known as 1982 SH1) was chosen for this honor because space is defined to begin at an altitude of 100,000 meters (100 kilometers, or 62 miles) above the earth's surface.

"Fifty years ago, a tiny satellite named Sputnik became the world's first artificial satellite. It seemed only fitting to commemorate the 50th anniversary of the dawn of the Space Age in some astronomical way," said Brian Marsden, director emeritus of the Minor Planet Center, which is located at the Smithsonian Astrophysical Observatory in Cambridge, Mass.

The Minor Planet Center serves as a clearinghouse for asteroid discoveries and assigns numbers in the order that observations are received and catalogued. Astronautica received the number 100,000 in October 2005. It was discovered by astronomer Jim Gibson of Palomar Observatory on September 28, 1982, only days before the 25th anniversary of Sputnik.

"Astronautica is not a particularly unusual object," Marsden said. "It just happened to be the 100,000th entry into our database."

The name was approved by the International Astronomical Union's Committee on Small Body Nomenclature, of which Marsden is a member. Currently, 14,077 asteroids have names while a total of 164,612 asteroids have been identified and numbered.

"Typically the discoverer names the asteroid, but the committee sometimes takes the initiative for special numbers," explained Marsden. "October 4, 2007 was an important anniversary, and we felt it was right to recognize it this way. We wanted a name with a broad international appeal, so we chose 'Astronautica,' which comes from the Latin for 'star sailor.'"

Astronautica is a space rock about a mile in size. Due to its small size and low mass, it is undoubtedly a misshapen lump like many asteroids.

Its orbit lies between the orbits of Mars and Jupiter. It circles the Sun at an average distance of about 175 million miles. A "year' on Astronautica lasts around 940 days-the equivalent of 2.6 Earth years.

Astronauts may visit Astronautica some day, using tethers to anchor themselves to the surface in the asteroid's weak gravity. However, that day is far in the future. Space travelers are likely to head to near-Earth objects like Eros well before making the long trip to the asteroid belt.

"Perhaps on the 100th anniversary of Sputnik, a tour group will visit Astronautica," Marsden grinned.

An orbital diagram of (100000) Astronautica is available online at http://www.cfa.harvard.edu/press/2007/pr200723_images.html

Headquartered in Cambridge, Mass., the Harvard-Smithsonian Center for Astrophysics (CfA) is a joint collaboration between the Smithsonian Astrophysical Observatory and the Harvard College Observatory. CfA scientists, organized into six research divisions, study the origin, evolution and ultimate fate of the universe.