How Do We Spot Near Earth Asteroids?
Did you ever wonder how NASA spots asteroids that maybe getting too close to Earth for comfort? Credit: JPL/NASA
A potentially hazardous asteroid the size of a football stadium is set to pass Earth this weekend, one of five asteroids to approach Earth in the coming days.
US space agency NASA keeps track of asteroids in space, including ones that are within 7.5 million kilometres of Earth.
Any object over 150m wide which approaches Earth within that distance, almost 20 times the distance to the moon, is deemed as potentially hazardous.
Most of these asteroids pass harmlessly with little fanfare.
One of these asteroids, known as 2002 NN4, is around 320m long, and is expected to approach within 5.09 million kilometres this weekend.
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2002 NN4 is a comparatively tiny asteroid, but is the largest that will approach Earth in the coming days.
It orbits the sun every 300 days and turns on its axis a little over every 14 days.
It’s expected to pass Earth at a speed of 11.146km/second on Saturday.
The next close approach of 2002 NN4 is after that is expected to be June 7, 2029.
Four other asteroids between 16m and 34m will pass as close as 2.94 million kilometres in the coming days.
NASA’s near Earth object close approach database shows some of the biggest asteroids that have come close to Earth over the last 120 years.
The biggest is 3122 Florence, estimated between 4km and 9km in diameter, which passed Earth on September 1, 2017, and is expected to do so again on September 2, 2057.