A meteoroid is a sand- to boulder-sized particle of debris in the Solar System. The visible streak of light from a meteoroid, heated as it enters a planet's atmosphere, and the glowing particles that it sheds in its wake is called a meteor, or colloquially a "shooting star" or "falling star".
Such relatively small rocks falling from space usually cause little damage or injury. However, the danger increases considerably when these cosmic missiles are only marginally larger. An object the size of a large house could easily wipe out a good-sized city...
Prof. Scott Hubbard of Stanford University, a former NASA manager, put it into more perspective. "You say 17,000 miles, that is huge. But remember all of those satellites out there that give us our global positioning, that tell our iPhones where we are, those are at 22,000 miles, so it is going to pass between Earth and the satellites that give us Direct TV every day. That's a close shave."
The asteroid -- a fuzzy dot zipping through space -- was discovered a year ago by Jaime Nomen, mild mannered dental surgeon by day, amateur astronomer by night.
It is called 2012 DA 14, and it will come scarily close to Earth on Friday, traveling from south to north, passing closest to Australia, Asia, and Eastern Europe. Closest approach is at 2:25 p.m. ET.
It will miss us by about 17,230 miles. To put that into perspective, the moon is 238,900 miles from Earth.
The asteroid and the meteor are not related; a meteor did not flake off the asteroid and tumble into our atmosphere. The two arriving here on the same day is just a coincidence.
Meteors (also known as falling stars or shooting stars):
Are meteoroids captured by a planet or other body
Appear when air friction heats the meteoroid, causing it to glow as it travels through the atmosphere, creating a bright trail
Occur on Earth every day as its orbit crosses through swarms of meteoroids in its path (most vaporize before becoming visible)
Can explode in the atmosphere
A meteor in central Russia has caused some injuries and shattered windows, reports say.
Brightly burning rocks could be seen for hundreds of kilometres as they crashed into the Ural region.
Chelyabinsk residents reported shaking ground, windows being shattered and car alarms being set off during the shower.
The traces from falling objects could be seen in Yekaterinburg, about 200km (125 miles) north of Chelyabinsk, a witness told the Reuters news agency.
The word meteor is derived from the Greek meteron, meaning something high up. Today, however, the term is used to describe the light phenomena produced by the entry of objects into Earth's atmosphere. A meteoroid is defined to be any solid object moving in interplanetary space smaller than a few meters in diameter...
Scientists estimate that 1,000 tons to more than 10,000 tons of meteoritic material falls on the Earth each day. However, most of this material is very tiny -- in the form of micrometeoroids or dust-like grains a few micrometers in size. (These particles are so tiny that the air resistance is enough to slow them sufficiently that they do not burn up, but rather fall gently to Earth.)
Where do they come from? They probably come from within our own solar system, rather than interstellar space. Their composition provides clues to their origins. They may share a common origin with the asteroids. Some meteoritic material is similar to the Earth and Moon and some is quite different. Some evidence indicates an origin from comets.
estimated two billion years old, it makes the Chicxulub Crater look like a spring chicken. Today, the original crater, which was caused by a meteorite about six miles wide, is mostly eroded away, but what remains is a dome created when the walls of the crater slumped, pushing up granite rocks from the center of the meteorite strike.
Second in size only to the Vredefort Dome, the Sudbury Basin is a 40-mile-long, 16-mile-wide, 9-mile-deep crater caused by a giant meteorite that struck Earth about 1.85 billion years ago. Located in Greater Sudbury, Ontario, the crater is actually home to about 162,000 people. In 1891, the Canadian Copper Company began mining copper from the basin, but it was soon discovered that the crater also contained nickel, which is much more valuable, so the miners changed course. Today, the International Nickel Company operates out of the basin and mines about 10 percent of the world's nickel supply from the site.