Asteroid hints at the smallest orbit

Astronomers announced a newly-discovered asteroid has the smallest orbit around the Sun ever seen for a space rock. It is also only the second known asteroid to have an orbit that lies entirely within the Earth's - the first was discovered in 2003.

Such asteroids are very difficult to detect because their position in relation to the Sun and the Earth means they rarely appear in the night sky.

The asteroid, designated 2004 JG6, was spotted earlier in May by Brian Skiff, part of the Lowell Observatory Near-Earth Object Search (LONEOS), in Flagstaff Arizona, US, reports newscientist.com.

The asteroid is probably no more than 0.62 miles wide (between 500 meters and 1 kilometer). It poses no danger to Earth, astronomers said, because its path will not directly intersect that of the planet any time in the foreseeable future.

There may be 50 asteroids comparable in size to 2004 JG6 orbiting entirely inside Earth's travels. But because they spend much of their time in the glare of the Sun, they are hard to find, inform yahoo.com

According to spaceref.com asteroids with orbits entirely within the Earth's orbit have been informally called "Apoheles," from the Hawaiian word for orbit. Apohele also has Greek roots: "apo" for outside, and "heli" for Sun. Objects orbiting entirely within Earth's orbit are thought by dynamicist William F. Bottke of Southwest Research Institute and colleagues to comprise just two percent of the total near-Earth object population, making them rare as well as difficult to discover. This is because they stay in the daylight sky almost all of the time. There may exist about 50 Apoheles of comparable size to or larger than 2004 JG6, but many of them are certain to be unobservable from the ground.

The first asteroid found entirely inside Earth's orbit was 2003 CP20, found just over a year ago by the NASA-funded Lincoln Laboratory Near-Earth Asteroid Research project, which observes near Socorro, New Mexico. Although larger than 2004 JG6, 2003 CP20 is a little more distant from the Sun.

LONEOS is one of five programs funded by NASA to search for asteroids and comets that may approach our planet closely. The NASA program's current goal is to discover 90 percent of near-Earth asteroids larger than 1 km in diameter by 2008. There are thought to be about 1,100 such asteroids.