Closest Ever Asteroid Passage Revealed

tricaric writes "Another asteroid passed, last March 31st, close to the Earth. This time it was only about 2 Earth radii from the Earth. The observation have been published only a few days ago, because 'Although the observed arc is only 44 minutes, the orbit is quite determinate and, given the exceptional nature of this close approach, the object is now receiving a designation.' Check out the ORSA animation!"

Comments

It was tiny...

[Selfbain]

If you read the article you can see that the asteroid was extremely small and would have broken up in the atmosphere.

It was only 6m in diameter -- harmless

[jerde]

Wouldn't it be prudent to put in the story text that the object is estimated to be only 6 meters in diameter?

The article states that an object that size would burn up harmlessly in the atmosphere. I'm not sure if that's correct or not... a 6 meter hunk of material would probably rain at least SOME material down on the ground, but I don't know if it would make a crater.

The point is that we didn't just narrowly escape certain doom... it was a small rock.

- Peter

Re:It was only 6m in diameter -- harmless

[Carnildo]

A six-meter rock, if it doesn't break up in the atmosphere, will make a respectable crater -- maybe even knock down a few buildings. If it does break up, the fragments won't be big enough to leave craters, but can still hit hard enough to damage buildings or kill people.

Re:It was only 6m in diameter -- harmless

[richie2000]

It's roughly two really small cars or one biggun. A Volvo 240 (the new yardstick for measuring asteroids, since I happen to have one handy) is just over 5 meters long. So if it helps, think of it as a large Volvo hurtling towards us from outer space at thousands of kilometers per hour (I'll save the detailed kph comparisons for later, but a standard Volvo 240 normally tops out at between 160 and 210kph depending on the engine).

Calculating how many Volvos there are in one Rhode Island is left as an exercise for the reader.

Re:It was only 6m in diameter -- harmless

[hankwang]

A six-meter rock, if it doesn't break up in the atmosphere, will make a respectable crater -- maybe even knock down a few buildings.

I'm not sure what the relative velocity of the object compared to the earth's was, but if we estimate 20 km/s and a mass of 300 tons, then the kinetic energy of this object is about 6e13 J. That is about 15 kilotons of TNT worth of kinetic energy that you have to get rid of during the 1-2 seconds it takes to cross the atmosphere. The Hiroshima bomb was about 20 kilotons. I doubt that you will get away with just a few destroyed buildings if the asteroid reaches the earth surface in one piece.

This one's a whole lot closer..

[dreamer-of-rules]

According to Earth Speeds, the Earth goes around the Sun at approximately 18.5 miles/sec, or 30 km/sec. In six hours the Earth will move 400,000 miles or 650,000 km around the sun. The radius of the Earth is roughly 4,000 miles or 6,500 km. So in six hours the Earth moves about 100 times its radius.

Basically, this latest asteroid is a lot closer.

Tunguska event

[FooAtWFU]

Well, the Tunguska event of 1908 is a case of one of these actually hitting the planet- though I guess it doesn't qualify as a "passage".

Re:Misleading Headline

[Begossi]

Right below the article there's small note explainning why it was a remarkable observation:

"is by far the closest ever observed astrometrically." The distinction is important, because the title of "closest ever observed" probably belongs to the well documented Great Daylight Fireball of 1972. On August 10th many witnesses, including a meteor expert, saw and photographed an object of about 2004 FU162's size fly through Earth's atmosphere, traveling from south to north along the Rocky Mountains of the U.S. From military satellite data it was later determined that the object passed 58 miles (93 km.) above a point in Montana during its journey. Gary Kronk's account of this event and subsequent investigations is great reading.