Number Of Potentially
Hazardous Asteroids
Grows To 200
By Robert Roy Britt
Senior Science Writer

Officials at the Minor Planet Center announced Thursday the addition of a 200th asteroid to a list of Potentially Hazardous Asteroids (PHAs).
These rocks in space can pass within 5 million miles of Earth and are brighter than magnitude 22, a measurement that suggests the asteroids are more than about 600 feet across.
The Massachusetts Institute of Technology's Lincoln Laboratory Near-Earth Asteroid Research project, known as LINEAR found the newly discovered asteroid, designated 1999 VP11, on Nov. 7. The project is responsible for the discovery of about one-third of all known PHAs, according to a statement from the Minor Planet Center.
The first PHA, known as Apollo, was discovered in 1932. But the search for Near-Earth Asteroids (NEOs) has only recently gained steam, and all but 15 of the PHAs have been found during the past 20 years. Most pose no real threat to Earth, experts say, though a handful could have their orbits altered by other bodies in the solar system, possibly sending them on a collision course with our planet at some point in the distant future.
"Only a fraction warrant any serious examination for a possible impact during the next half-century or so," said Brian Marsden, director of the International Astronomical Union's Minor Planet Center.
Other significant Earth-approaching asteroid search programs include the University of Arizona's Spacewatch project (12 PHAs discovered), the Jet Propulsion Laboratory's Near-Earth Asteroid Tracking program (six), the University of Arizona's Catalina Sky Survey (five), and the Lowell Observatory Near-Earth Object Program (four). Amateur astronomer Roy Tucker has discovered two PHAs.