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Asteroid To Be Naked-Eye Visible In 2029
An anonymous reader writes "SPACE.com is reporting that asteroid 2004 MN4 will fly so close to Earth in 2029 that it'll be visible to the naked eye. Other than barely-visible Vesta, this is a first. And 2004 MN4 will be about magnitude 3.3 -- like a dim but easily visible star. A moving star in this case. You might remember 2004 MN4 is the one that sparked worry, in December, that it would hit Earth. No worries, NASA says, just a once-in-a-millennium sky show."
They've been tracking it for a while, and NASA has some pretty good quadrature software for numerical solutions to the N-body problem. I don't see any particularly precise figures in the summary anyway, and I'm not going to read the article, am I?
Go look at this JPL press release. See the white line in the closeup view? That's the error on the position. If that white line intersected Earth, then there would be some probability that this asteroid would strike us.
They can predict these things through hundreds of observations from observers around the world. Through mathematical modelling they can calculate what the orbit is going to be. As more observations come in and as the forecast time comes closer the errors go down.