Asteroid Highlighted as Impact Threat

Maggie McKee writes "The asteroid Apophis has been traversing the void of space for untold years; in just a few decades time it will make a very close pass to Earth, and could make an unwelcome stop on our planet's surface. Even still, it's nothing to get too worked up about. The 20-million-tonne object has a 1 in 45,000 chance of hitting the Pacific Ocean in early April of 2036. If it did hit, it could trigger a tsunami that would do an untold amount of damage to the California coastline and many other places on Earth. Despite the low level of the threat, it's still a real enough danger to prompt the United Nations to develop a protocol about the scenario. We'll get a closeup look at the object in 2029, and at that point we should have a better idea of what 2036 will bring us."

Comments

2007 CA19

[crontabminusell]

The object 2007 CA19 has a better chance (as of right now) of hitting the Earth than 99942 Apophis (2004 MN4) does. The former is also about four times larger than the latter and would have more than double the velocity at impact if it were to hit.

Re:The Pacific

[purfledspruce]

Actually, the uncertainty mostly isn't due to error in position; it's due to the fact that, when we observe a NEO, it's a point of light in the sky. We really don't know how far away it is. If it's near to the Earth and Sun, it moves more quickly; if it's farther away, it moves more slowly. If you remember that things move in circles or ellipses around the Sun, then you might get the idea that the uncertainty "ellipse" (due to a small error in position left-right, but a very large error in depth) due to the different orbital velocities, it "stretches out" over time, wrapping the ellipse's major axis around the Sun until it's basically a straight line.

There's a fantastic animation of this process at Spaceguard's site, just scroll down to the second animation.