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‘Twilight telescopes’ are finding ‘city-killer’ asteroids


When it comes to looking for asteroids, we have a blind spot. It may seem counterintuitive, but the most important asteroid discoveries are now being made in twilight, when astronomers are able to look close to the horizon — and close to the sun — for little-known asteroids that orbit inside the orbits of Earth, Venus and even Mercury. 

In a perspective published in Science today, asteroid-hunter Scott Sheppard of the Carnegie Institution of Science highlights the new “twilight telescope” surveys and the riches they’re beginning to discover. That includes the first asteroid with an orbit interior to Venus and one with the shortest-known orbital period around the sun, both of which have been unearthed in the last two years. It also includes “city-killers,” asteroids large enough that if they were to impact Earth, the damage would be severe.





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