For helping to find asteroids, NASA has set up a contest with cash awards. In 2012, the agency said that "more potentially hazardous asteroids, or PHAs, are closely aligned with the plane of our solar system than previous models suggested." NASA hide caption
A NASA artist's illustration depicts an asteroid belt around a star that the space agency says is "the same age and size as our Sun." NASA/JPL-Caltech hide caption
These NASA/ESA Hubble Space Telescope images reveal a never-before-seen set of six comet-like tails radiating from a body in the asteroid belt designated P/2013 P5. NASA, ESA, D. Jewitt (University of California, Los Angeles), J. Agarwal (Max Planck Institute for Solar System Research), H. Weaver (Johns Hopkins University Applied Physics Laboratory), M. Mutchler (STScI), and S. Larson (University of Arizona) hide caption
This artist's drawing shows the Wide-field Infrared Survey Explorer, or WISE spacecraft, in its orbit around Earth. NASA/JPL-Caltech hide caption
Actor Bruce Willis appears on the surface of an asteroid in a scene from the movie Armageddon. Frank Masi/AP hide caption
Radar images of asteroid 1998 QE2, taken when the cosmic traveler was about 3.75 million miles from Earth, revealed that the asteroid, with a 1.7-mile diameter, has a moon or satellite revolving around it. NASA/JPL-Caltech/GSSR hide caption
Debris: friend or foe? Both! Illustration/NASA hide caption
An illustration of what asteroid 2012 DA 14 may look like as it approaches Earth. NASA/JPL-CalTech/EPA /LANDOV hide caption
A meteor's vapor trail above the city of Chelyabinsk, Russia, on Friday. Vyacheslav Nikulin /EPA /LANDOV hide caption
An illustration of what asteroid 2012 DA 14 may look like as it approaches Earth. NASA/JPL-CalTech/EPA /LANDOV hide caption
An artist's impression of a gamma-ray burst, a powerful jet of energy lasting from less than a second to several minutes. The most powerful events in the universe, they are thought to be mostly associated with the explosion of stars that collapse into black holes. A. Roquette/ESO hide caption
NASA says an impact with a 500-km-diameter asteroid would effectively sterilize the planet. Don Davis/NASA hide caption