Tracking asteroids and other objects that could kill us, is still largely based on amateur and professional astronomers making chance observations with regular telescopes.
Space is very, very large, and asteroids, even the big Earth-killing ones, are tiny in comparison. So how exactly do astronomers keep us informed about the various rocks tumbling through our solar system? High tech solutions are being developed for the future, but for now, most of the work is actually done with an old fashioned telescope.
“It all begins with an observer making observations,” says Gareth Williams of the Minor Planet Center. The center is the clearinghouse for minor planet and asteroid documentation, “They can be observing known objects, or they can be searching for new objects, but even if they’re searching for known objects, just to take a pretty picture or some reason, new objects can come into the field. About one in 1,000 of these new objects turn out to be an object that’s moving anomalously when compared to other objects in the frame,” he explains.
When an astronomer discovers an object with anomalous motion, they report it to the Minor Planet Center, which compares the finding to known Near Earth Objects (NEOs). If it’s not in the database, it gets added to the list.
So far, amateur and professional astronomers have found more than 10,000 NEOs, and an estimated 90% of the ones that could kill us off have been found. However, tracking anything smaller than 1km is difficult, and there’s plenty of rocks out there that could cause us harm. “NASA has not even come close to finding and tracking the 1 million smaller asteroids that might only just wipe out a city, or perhaps collapse the world economy if they hit in the wrong place,” says Ed Lu, CEO of a non-profit organization building a NEO hunting space telescope called Sentinal asteroid observatory. So far, only 10% of asteroids 140m across have been found, and those can still cause some damage.