Asteroid visit not unusual, not dangerous
Posted February 8, 2013
Updated February 14, 2013
2012 DA14, a rocky asteroid about 150 feet wide, will pass within 17,200 miles of Earth on Feb. 15, at 2:24 p.m. ET. That's 1/13th the distance of from the Earth to the Moon and the closest an object of this size has come to Earth since NASA's Near Earth Object (NEO) office at the Jet Propulsion Laboratory began regularly watching the skies for threats in the 1990s.
The asteroid will pass well inside the 22,200 mile orbit of geosynchronous satellites but outside the 13,000 mile orbit of GPS satellites. Fortunately, the zone where 2012 DA14 will pass is relatively satellite-free. 2012 DA14 also poses no threat to astronauts aboard the International Space Station in its 230-mile high orbit.
The asteroid itself is not unusual. There are many in Earth's general neighborhood ranging in size from a few feet to several miles across.
Asteroids pass by Earth regularly as well. This week alone, 11 asteroids tracked by the NEO office passed Earth. Most were well outside the orbit of the Moon, however a roughly school bus-sized one known by its catalog name of 2013 CY32 passed about 115,000 miles from Earth this past Tuesday. Another 11 in addition to 2012 DA14 will pass next week.
The orbit of 2012 DA14 is now well known. It has been tracked both optically with telescopes and via radar from the Arecibo Observatory in nestled in the mountains of Puerto Rico and the Goldstone tracking station southern California desert. NASA's NEO office is confident that "it will definitely not hit Earth." Earth has not always been so lucky.
50,000 years ago, a similar sized asteroid created Meteor Crater in central Arizona. That asteroid was iron based which helped it create a nearly 3/4 mile wide crater in the sandstone desert.
Another similar sized object entered the atmosphere, exploding over Siberia in 1908 leveling 800 square miles of forest. Damage of asteroids of this size is limited to the immediate area around the impact site rather than the global devastation suggested by Hollywood.
As much as I'd like to set my telescope up in the backyard and have a look at next week's visitor, any telescope other than large, well-placed ones used for research will have difficulty tracking the swift moving, tiny, dim object.
“The asteroid will be racing across the sky, moving almost a full degree (or twice the width of a full Moon) every minute," says Don Yeomans of NASA's Near Earth Object Program.
It also will pass on the night side of Earth, over the Indian Ocean and won't be visible from North America.
Calculations show that Earth's gravity will alter the orbit of this asteroid on Friday. This will reduce the orbital period to 317 days as well as change the shape of its orbit. The next time we even see this asteroid inside out moon's orbit won't be for another 75 years.
Tony Rice is a volunteer in the NASA/JPL Solar System Ambassador program and software engineer at Cisco Systems. You can follow him on twitter @rtphokie.