Potentially hazardous asteroids (PHAs)

Last year, NASA's Near-Earth Object Wide-field Infrared Survey Explorer (NEOWISE) survey found that more potentially hazardous asteroids, or PHAs, are closely aligned with the plane of our solar system than previous models had suggested.

PHAs are the subset of near-Earth asteroids (NEAs) with the closest orbits to Earth's orbit, coming within 5 million miles. They are also defined as being large enough to survive passage through Earth's atmosphere and cause damage on a regional, or greater, scale.

The dots represent a snapshot of the population of NEAs and PHAs that scientists think are likely to exist based on the NEOWISE survey. Positions of a simulated population of PHAs on a typical day are shown in bright orange, and the simulated NEAs are blue. Earth's orbit is green.

These results have found about 4,700 objects, plus or minus 1,500, with diameters larger than 330 feet. The NEOWISE team estimates that only about 20 percent to 30 percent of the PHAs thought to exist have actually been discovered so far.