Near Earth Asteroids or Potentially Hazardous Asteroids (<a href="http://neo.jpl.nasa.gov/neo/groups.html">PHAs</a>) 
 are space rocks larger than approximately 100m that 
 can come closer to Earth than 0.05 AU. None of the 
 known PHAs is on a collision course with our planet, 
 although astronomers are finding <a href="http://www.minorplanetcenter.org/iau/lists/Dangerous.html">new 
 ones</a> all the time.