Near-Earth asteroid with weird retrograde orbit discovered: 2009 HC82

Saturday, May 02, 2009

A pretty interesting discovery was announced today, an asteroid with a retrograde orbit, also fairly large (2-3 km or so in diameter, thus surface area of around 12 - 28 km²), and close enough to Earth that it's surprising that it hasn't been discovered until now. Its current position is right here:

Since it's retrograde that means it's moving away from the Sun at the moment and so won't be coming in for a close encounter for a while. It gets as far away as 4 AU from the Sun and Earth, and will have the following close encounters over the next few years:

  • 3 January 2012: 0.158 AU
  • 28 April 2012: 0.786 AU
  • 15 February 2015: 0.642 AU
  • 11 June 2015: 0.27 AU
  • 14 August 2018: 0.582 AU
  • 24 October 2021: 0.652 AU
As you can see, it's a bit of luck that we've discovered it before the close encounter in 2012 as that's the closest it will be to Earth for...well, for quite some time (if you want to find out yourself see the page here, but note that it always shuts down Firefox when I use it so I only view it with Opera). With the retrograde orbit you can see that there are often two close encounters, once when the asteroid is coming in towards the Sun and the Earth is making its way in the opposite direction, and then again as it goes around the Sun and back out the other side, when it nears the Earth again.

This close approach in 2012 is only 60 times the distance from the Earth to the Moon.

Finally, for another article on the discovery see here.

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