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What are the Chances of the Earth Being Struck by an Asteroid?

-- Brittany | June 12, 2020

Artist impression of a supermassive black hole

Question:

What is the chance of a devastating impact asteroid going unnoticed until it hit earth?
If one large enough to cause significant damage and death was to come from the direction of the sun, would we ever be able to see it before it impacts earth?

-- Brittany

Answer:

You are referring to what NASA calls “Potentially Hazardous Asteroids (PHAs)”. This sub-class of asteroid is defined as those whose orbits bring them within 0.05 Astronomical Units (AU), or about 7.5 million kilometers and whose absolute magnitude is 22 or dimmer. A very nice description of PHAs by the Rubin Observatory describes their potential for catastrophic impact as about 1% within the next 100 years, which is quite low. The Rubin Observatory, like several other observatories, have or will soon begin monitoring campaigns to search for and track PHAs.

-- Jeff Mangum

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