Tomorrow is Asteroid Day, an annual event to highlight the potential risks that near-Earth objects (NEOs) such as comets and asteroids pose to Earth.
Launched in 2014 by Queen guitarist and astrophysicist Brian May and film director Grigorij Richters, the event was backed by prominent scientists across the globe, including Stephen Hawking, Neil deGrasse Tyson and Bill Nye.
Now in its fourth year, Newsweek has spoken to Paul W. Chodas, Manager of the Center for Near-Earth Object Studies at NASA’s Jet Propulsion Laboratory about the risk asteroids pose to the planet.
What are near-Earth objects?
We affectionately call these NEOs. They are asteroids and comets that are on orbits which bring them into the inner solar system, in the general vicinity of the Earth. To be nerdy and precise, they are small bodies whose orbits bring them to within 1.3 astronomical units of the Sun, where 1 astronomical unit is the average Earth-Sun distance. Keep in mind that asteroids and comets orbit the Sun just like the planets.
Why is it important to monitor the sky for them?
It’s important to monitor NEOs because one of these small bodies might be on a collision course with the Earth! Fortunately, it’s a very small chance…But scientists think that the dinosaurs became extinct because of the collision of a large 10km (6.2 miles) asteroid 65 million years ago. And NEOs continue to pose a hazard—just a few years ago, in 2013, a two-meter asteroid entered the atmosphere over Chelyabinsk, Russia, causing an explosion high in the atmosphere of nearly half a megaton, resulting in thousands of injuries just from the shock wave.
How many have we found so far, and how many more are thought to be out there?
Over 16,000 NEOs have been found so far, if we count all sizes. Objects smaller than about 50 meters in size will almost certainly disintegrate in the atmosphere without producing much damage if they are on a collision course. Roughly 12,000 known NEOs are larger than 50 meters in size, but there are a lot more to find. The numbers of NEOs go up exponentially as we consider smaller and smaller sizes, but the hazard is much lower for smaller asteroids.
What is currently being done to identify more NEOs?
NASA operates several telescopes dedicated to searching for NEOs. The two largest programs operate out Tucson Arizona and Haleakala in Hawaii. Over the last 19 years, NASA-funded search programs have found over 90 percent of the known NEOs. But there’s more work to do. The U.S. Congress has assigned NASA the goal of finding 90 percent of the NEOs larger than 140 meters in size, of which there are probably about 20,000. So far we have found only about a third of these.