Potentially Hazardous Asteroids and Their Orbits

The Near Earth Object Program at the Jet Propulsion Laboratory is currently tracking 1391 "potentially hazardous asteroids." You can even click on them and see their orbits in a cool little java app. Like I didn't have enough to worry about.

Most of them are actually so radically out of sync with our position that they won't be a problem in any of our lifetimes. But it's pretty cool that they're being monitored constantly and we're always increasing the accuracy of the orbit predictions. You can even download the orbital info yourself.

Science is awesome.

It's scarier when you see the information visually...

The ones that cross Earth's orbit are in red, the ones that come close are in yellow.

I also love JPL's small-body database, which tracks every known asteroid and comet. It even includes additional information (where available) such as the object's size and probable composition.

That is just absolutely amazing. Crowded place!

Well, crowded astronomically. The vastness between everything is still mind bottling.

Still, even in the first few seconds, just watch the orbit of earth, and it's amazing how many come close enough to intersect the graphical representations.

Also, it was interesting to watch some of those red ones that slingshot around the sun, out almost to Jupiter, then get pulled back in for another pass.

Mixolyde wrote:

That is just absolutely amazing. Crowded place!

Douglas Adams wrote:

Space is big. You just won't believe how vastly, hugely, mind- bogglingly big it is. I mean, you may think it's a long way down the road to the chemist's, but that's just peanuts to space.

NASA actually ran some numbers for the Dawn Mission, which has visited Vesta and is heading towards Ceres. Vesta and Ceres represents about a third of the total mass of the asteroid belt. Tack on Pallas and Hygiea and you're at about half the mass.

Asteroids are not distributed uniformly in the asteroid belt, but could be approximated to be evenly spaced in a region from 2.2 AU (1 AU is 93 million miles, or the average distance between Earth and the Sun) to 3.2 AU from the Sun and extending 0.5 AU above and below the ecliptic (the plane of Earth's orbit, which is a convenient reference for the solar system). That yields a volume of roughly 16 cubic AU, or about 13 trillion trillion cubic miles. (Note: space is big!)

If there were 2 million asteroids 1 mile or larger in that volume, each asteroid would have 6.7 million trillion cubic miles to itself, so the average distance between individual asteroids 1 mile in diameter or larger would be about 1.9 million miles. That is nearly 8 times the distance between Earth and the Moon.

Asteroid belts are often depicted in science fiction as boulders ranging in size up to many miles, jostling for space, nearly bumping into each other, often as ships dodge and swerve around them. As you can see, that is not the case at all. Although I have made some simplifying assumptions here, and different choices would yield a somewhat different answer, the conclusion is the same: the asteroid belt is mostly empty space, and the asteroids orbit the Sun largely in isolation. Encounters among them are rare.

And this:

To bring this down to a more tractable scale, we can imagine Dawn's journey through the asteroid belt to Vesta as a trip from New York City to Los Angeles, with rocks littered along the way. In this case, along the entire route to a bizarre and forbidding land, the nearest we would come to one of these rocks would be 3.4 kilometers (2.1 miles) -- hardly a close call. At that distance, it would be difficult even to detect the rock, as it would be a mere 1.5 centimeters (less than 5/8 of an inch) in diameter; this corresponds to an asteroid less than 5 kilometers (under 3 miles) across. Even looking out to 20 kilometers (12 miles) during our trek, the largest object we would pass would be just 3.4 centimeters (1.3 inches), representing a 10-kilometer (6-mile) asteroid Dawn will miss by 15 times the distance between Earth and the moon.

Not this again...

No worries my fellow GWJers.

For I have sharks with frickin' lasers on their heads to gently nudge threatening asteroids from their trajectory.

fangblackbone wrote:

Not this again...

I work in weather satellites, I know what the actual danger is.

It's just cool.

Yes it is.

Don't worry about this stuff. If we're going to get hit, statistically speaking we'll never see it co