There are currently 1,400 potentially hazardous asteroids that could pass close to Earth, according to latest data revealed by Nasa. An image mapping the orbits of all the potentially hazardous asteroids (PHAs) provides a graphic of the crowded cosmic activity. These asteroids are considered hazardous because they are fairly large - at least 460 feet or 140 meters in size. This graphic shows the orbits of all the known Potentially Hazardous Asteroids (PHAs), numbering over 1,400 as of early 2013. These are the asteroids considered hazardous because they are fairly large (at least 460 feet or 140 meters in size), and because they follow orbits that pass close to the Earth's orbit
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These asteroids are classified as 'hazardous' because they are at least 140 meters in size and could come within 4.7 million miles of Earth's orbit
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However, none are considered a threat over the next hundred years
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NEOCam mission will track these asteroids and other near-Earth objects
However, Nasa claims that being classified as a PHA does not mean that an asteroid will impact the @placeholder.