NASA’s Near-Earth Object Wide-field Infrared Survey Explorer (NEOWISE) telescope has detected 97 heretofore-unknown objects in our solar system, 10 of which have been characterized as “potentially hazardous objects” (PHOs).
Of the 97 objects, 28 were near-Earth objects (NEOs), five were comets and 64 were asteroids in the Asteroid Belt.
PHOs are defined as space objects at least 100 meters in diameter that may come within 4.6 million miles of Earth. Any smaller and they're likely to disintegrate in the atmosphere, any farther away and they'll simply miss Earth entirely. NASA defines them as asteroids and comets that are guided "by the gravitational attraction of the planets in our solar system into orbits that allow them to enter Earth's neighborhood."
These objects, mostly asteroids, have a chance to hit Earth and cause regional or even global devastation within the next 100 years. Since the 1990s, the number of PHOs on record has increased tenfold as a result of improvements in telescopes and observation.