Original URL: http://www.theregister.co.uk/2013/01/06/asteroid_fly_by_excitement/

Sky watchers prep for early 2013 asteroid fly-bys

No ‘Lucifer’s Hammer’ this time

By Richard Chirgwin

Posted in Science, 6th January 2013 21:06 GMT

NASA asteroid-watchers are eagerly awaiting a January 9 fly-by of the maybe-dangerous-one-day 99942 Apophis to improve their understanding of its orbit.

Named after an ancient Egyptian god of evil and darkness, the asteroid was first detected in 2004. While the earliest observations suggested a possible collision with Earth in 2029, that threat was downgraded as more observations were collected.

However, since NASA still thinks there’s a “tiny chance of an impact” in April 2036, they’re looking forward to this week’s pass, when 99942 Apophis will pass 14.5 million kilometers away from Earth.

The JPL’s Lance Benner told AFP (via Phys.org) the agency will be measuring “the asteroid’s distance and line-of-sight velocity” to improve its ability to predict the comet’s motion.

In particular, NASA wants to try to measure the impact of the Yarkovsky effect on 99942 Apophis. This is the name given to the alternating heating and cooling of the asteroid as it rotates, which can impart a small momentum to the object and skew its motion.

Yet another close encounter is set for February 15, when the 57-meter 2012 DA14 will come closer to Earth than our cloud of geostationary satellites. Its fly-by will skim just 34,500 kilometers away from us.

That will be close enough for amateurs with decent instruments to catch it briefly, if it’s not in Earth’s shadow during the pass.

2012 DA14 is quite the regular companion of Earth, passing us twice a year. ®