Washington, Sep 30: Latest NASA observations show there are significantly fewer near-earth, mid-sized asteroids lurking in space than previously thought.
Scientists say this discovery may indicate the hazard to earth could be somewhat less than previously thought.
Astronomers estimate there are roughly 19,500 -- not 35,000 -- mid-size near-earth asteroids, a majority of which remain to be discovered, the Astrophysical Journal reports. More research is needed to determine if fewer mid-size objects (between 330 and 3,300-ft wide) also mean fewer potentially hazardous asteroids, those that come closest to earth.
However, the majority of these mid-size asteroids remain to be discovered, according to a NASA statement. The results come from the most accurate census to date of near-earth asteroids, the space rocks that orbit within 195 million km of the sun into earth's orbital vicinity.
NASA's Wide-field Infrared Survey Explorer (WISE) observed infrared light from those in the middle to large-size category. The survey project, called NEOWISE, is the asteroid-hunting portion of the WISE mission.
"NEOWISE allowed us to take a look at a more representative slice of the near-earth asteroid numbers and make better estimates about the whole population," said NEOWISE project principal investigator Amy Mainzer, who led the study.

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