Hundreds Of Near-Earth Asteroids Have Been Lost Since We First Saw Them

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One day an asteroid may have our name on it. No such asteroid is known yet, but to prepare for the worst, we really need to make sure we’re tracking everything.

So a paper available on arXiv, from a team of astronomers at the Harvard-Smithsonian Center for Astrophysics in Massachusetts, will be some cause for concern. They say we’ve lost hundreds of asteroids found in the last few years, although don’t worry, it’s not all bad news.

As picked up by New Scientist, the study looks at the number of asteroids detected by the Minor Planet Center’s Near-Earth Object Confirmation Page (NEOCP) between 2013 and 2016. In total, about 17,000 near-Earth asteroids (NEAs) were found.

What’s more concerning, though, is that more than 900 had been seen once, and never seen again in other surveys of the night sky. And if we want to keep an eye on all asteroids, we really need to lower this number.

The reason so many have been lost is the nature in which they are tracked. If a survey spots one, it could be hours before that discovery is announced, or until another telescope or survey is available. In that time the asteroid could have traveled across the sky and out of sight. With just one sighting, it’s orbit cannot be tracked – you really need four or more.

“Because the initial tracklet [asteroid] cannot be represented by a single orbit, its positional uncertainty grows rapidly within a few hours of observation,” the team wrote in their paper.

“Late submission can reduce the chances of collecting follow-up data due to this growing uncertainty, as well as to the day/night limitations and availability of follow-up telescopes around the world.”

There are other factors too. One is that the asteroid might simply be moving too fast to be tracked, or that it's too dim. Bad weather can also hamper observations, as can the brightness of the Moon on rare occasions.

What about that good news? Well, the study’s lead author Peter Vereš told New Scientist that the largest asteroids that could destroy Earth are “basically all found”. These are ones more than a kilometer in size, so there's no need to panic too much just yet.

Sure, a smaller asteroid like the Chelyabinsk meteor over Russia in 2013 slips through the net every now and again. And we do really need to get better at tracking asteroids of all shapes and sizes, but we don't know of any sizeable rocks that will hit us through the next century. Still, it's worth keeping an eye out.

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