ASTEROID TO BUZZ EARTH THIS WEEK: When the sun rose over Chelyabinsk, Russia, on Feb. 15, 2013, at first it seemed like an ordinary day. Then the space rock hit. Without warning, the morning sky lit up with a second sun as shock waves shattered windows in hundreds of buildings around the wakening city.
The impactor flew out of the blue, literally from the direction of the sun where no telescope could see it, and took everyone by surprise. Years later, meteorite hunters are still finding pieces of the “Chelyabinsk asteroid” that rained down after its 17m-wide body disintegrated in the atmosphere.
A similar asteroid is approaching Earth this week, but this time NASA knows its coming. 2012 TC4 measures somewhere between 10 m and 30 m wide, and on Oct. 12th it will pass 43,500 km above our planet’s surface, about 1/8th the distance to the Moon. The flyby is so close, Earth’s gravity will significantly alter the asteroid’s trajectory before it exits the Earth-Moon system.
“We know the orbit of 2012 TC4 well enough to be absolutely certain that it won’t hit Earth,” says Paul Chodas, manager of the Center for Near-Earth Object Studies (CNEOS) at JPL,”but we haven’t established its exact path just yet.”
To get a better handle on the asteroid’s orbit (and possible future encounters), an international network of telescopes will monitor 2012 TC4 as it goes by. Pinging the asteroid with its Goldstone radar, NASA hopes to learn much about the space rock’s physical properties. The space agency will even exercise some aspects of its planetary defense systems.
This asteroid is too small to see with the naked eye. However, skilled amateur astronomers using 8+ inch telescopes will be able to observe it. At peak brightness, 2012 TC4 will shine like a 13th magnitude star as it zips through the constellations Capricornus and Sagittarius, according to AstroBob, who has detailed observing tips.