Cosmic Coincidence: Asteroid or meteor? What’s in a name?

Cosmic Coincidence

Maybe somebody misread the calendar. Are we sure this isn't Friday the 13th?

The earth is safe tonight after a well advertised close call with Asteroid 2012 DA14 Friday.

Image: NASA

But the well forecast asteroid fly-by was upstaged by a surprise meteor impact that sparked a spectacular fireball and injured hundreds as it slammed into Siberia early Friday.

What's the difference between an asteroid and a meteor? And how do we detect & track big chunks of rock flying through space that might impact earth?

We'll take a look in this spacey edition of Updraft.

50 feet wide estimated size of the meteor that crashed into Siberia Friday injuring over 1,000 people

150 feet wide estimated size of Asteroid 2012 DA14 as it flew by earth Friday

17,200 miles above earth (inside orbit of geostationary weather and communications satellites)

Shooting Gallery: Beware flying objects

It's a rare day when we get a close asteroid fly by from a chunk of space rock half a football field wide. It's downright scary when a school bus sized meteor creates a giant fireball and slams into Siberia the same day.

NBC's Andrea Mitchell has a good summary of the events.

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The videos coming in from the event are pretty scary. Ever wonder what it's like in the "impact zone" of a meteor?

This Guradian UK video compilation is the best raw video I've seen so far.

CBS News documents the rare twin threat.

As predicted, a 150-foot-wide asteroid streaked safely past Earth Friday, making a record close approach just 17,200 miles above the Eastern Hemisphere, well inside the orbits of geostationary communications and weather satellites.

The close encounter came on the heels of a spectacular fireball over western Siberia earlier in the day, a 10-ton meteoroid that broke up in the atmosphere with a supersonic air blast that set off car alarms, shattered windows and sent hundreds of people to area doctors and hospitals with injuries from flying glass and debris.

In a cosmic coincidence, the meteor upstaged asteroid 2012 DA14, a much larger, unrelated body that passed above Indonesia at 2:24 p.m EST. The asteroid passed so close to Earth, in fact, that the planet's gravity was expected to bend its trajectory slightly, putting it in a slightly different orbit and reducing the chances of additional close encounters in the foreseeable future.

"Meteor-ology"

Weather forecasting is called "meteorology" because we essentially track "hydrometeors"... drops of rain, snow and ice as they fall (usually gently) earthward.

Thankfully we're not tasked with tracking school bus sized chunks of rock on Doppler.

Leave that to NASA's Near-Earth Object program. These are the scientists who have a potentially much more important job. Find big space rocks that can make rare but devestating impacts on earth.

"What an exciting day!" said Paul Chodas, a scientist with NASA's Near-Earth Object program. "It's like a shooting gallery here, we have two rare events of near-Earth objects approaching the Earth on the same day."

Asteroid or Meteor? What's in a name?

Here's a great explanation from Cosmic Log on the various terms used to describe various space rocks that hurtle through space at 5 miles per second. The take away?

Size matters.

What exactly fell on Russia's Chelyabinsk region on Friday? Was it an asteroid, meteor, meteoroid, meteorite or fireball? You could make a case for "any of the above," depending on your definitions and the precise part of the phenomenon you're trying to describe.

The Chelyabinsk incident is the biggest known cosmic impact since another Russian blast that occurred a century ago, the Tunguska incident of 1908. There's good reason for that notoreity: Hundreds of injuries were reported. NASA estimated that the energy released by the Chelyabinsk impact amounted to 300 kilotons of TNT, which suggests the blast was more than 10 times as powerful as the atom bombs that were dropped on Japan at the end of World War II.

NASA's assessment put the Chelyabinsk object's width at 15 meters (50 feet), and its mass at 7,000 tons. Much of that mass burned up during the object's atmospheric entry at a velocity of 40,000 mph (18 kilometers per second). "The fireball was brighter than the sun," the space agency said in a statement.

Astronomers use different terms to describe cosmic objects of different sizes: When the rock is no wider than a meter (3.3 feet), it's known as a meteoroid. But once you start getting into the 1- to 10-meter range, the term "asteroid" applies. Earlier estimates suggested the Chelyabinsk object was a meteoroid, but the latest assessment would put it in the class of a small asteroid.

Bill Cooke, who heads the Meteoroid Environment Office at NASA's Marshall Space Center, said the object was "a small asteroid or a large meteoroid, depending on how you want to define it."

What a crazy day.

I think I'll stick to tornadoes, hurricanes and blizzards.

PH