What are Potentially Hazardous Asteroids? NASA explains 

Huge asteroids have crashed into Earth many times in the past and it can happen again. While many more asteroids miss Earth, the danger is permanent and that is where it becomes important for space agencies like NASA to track each and every flying object that is big enough to worry humanity. 

Potentially Hazardous Asteroids (PHAs) are a subset of Near-Earth Asteroids particularly important for study as they have the potential to cause damage on the Earth’s surface if they impact. 

Due to the Earth’s gravitational pull, the planet tends to attract celestial objects like asteroids towards it leading to surface impacts.

But how big an asteroid can end all life on planet Earth? Well, NASA scientists estimate that an asteroid would have to be about 96 km wide to completely and utterly wipe out life on Earth, though smaller asteroids also have the potential to cause regional damage. 

Asteroids which come within 8 million kilometers of Earth are classified as Potentially Hazardous Asteroids by NASA, as they pose a risk to Earth if they get caught within the planet’s gravitational field which can send them tumbling towards the planet. 

The responsibility for keeping an eye on these asteroids falls to NASA’s Planetary Defense Coordination Office (PDCO), managed in the Planetary Science Division at NASA Headquarters in Washington, D.C. 

NASA uses its various ground and space-based telescopes such as the NEOWISE, Pan-STARRS and the Catalina Sky Survey to monitor and flag these space rocks. 

Although asteroid flybys are frequent, people will be relieved to know that none of them will be any potentially “world-ending” asteroids. 

In fact, such an asteroid is not expected for at least a century or more, according to Davide Farnocchia of NASA’s Center for Near-Earth Object Studies (CNEOS). 

Having said that, there is a clear and present danger from new asteroids are being found on a regular basis.