This year we're getting asteroids for all occasions. First the Halloween asteroid decided to swing by for some trick-or-treat action, and now a Christmas Eve asteroid wants to fill all our stockings with carbonaceous chondrites1.
The asteroid 163899, also known as 2003 SD220, will pass by Earth at a harmless distance of 6.7 million miles--that's about 28 times as far as the moon. It's a big asteroid, estimated to be between 0.5 and 1.5 miles wide, and it's zooming around at about 5 miles per second. (Beat that, Rudolph.)
When it passes by on Christmas Eve, you'll need a telescope and some amateur astronomy experience to find it. But no worries, if you miss it, it'll be back again in December of 2018 and 2021. NASA's asteroid radar research group notes:
The 2015 apparition is the first of five encounters by this object in the next 12 years when it will be close enough for a radar detection. By obtaining radar ranging measurements at each observing opportunity, it may be possible to detect non-gravitational perturbations due to the Yarkovsky effect. If so, then we can obtain an estimate of the object's mass, information that is invaluable for understanding the object's bulk density and internal structure.
What we learn from the Christmas Eve asteroid could be particularly important since NASA is thinking about sending humans to it in the decades to come.
: Note: The asteroid is not passing nearly close enough to fill our stockings with rocks, and even if it could, we're not entirely sure they'd be carbonaceous chondrites. However, carbonaceous asteroids make up 75 percent of the asteroids that we know of. They're dark in color and, as the name implies, contain a lot of carbon ... just like a certain Christmas stocking stuffer.