I had a good night under the stars last night. Temperatures in the 20s made it easy to be outside for a change. It also meant I could make a few time exposures without having to worry about running out of battery power. Winter’s Milky Way is fainter and less textured than the summer version with its chunky star clouds. From a rural site, it slices diagonally from right to left across the southern sky and reminds me of rising smoke from a smouldering campfire. Knowing that it’s jammed with billions of stars thousands of light years thick jazzes my brain every time I see it.
A 36-foot wide asteroid skimmed near Earth at 9:30 a.m. CST this morning passing only 36,750 miles away before zooming back into the deeps at more than 21,000 mph. No danger was ever expected from 2012 BX34, since a rock that size would disintegrate into pieces if it were to strike our atmosphere. At best we might expect a few meteorites. No worries. The asteroid’s path was well known beforehand and any chance of a collision ruled out.
Some amateur astronomers saw and photographed the object, but it was challenge, because 2012 BX34’s tiny size meant it was faint – only about 15th magnitude at best.
Several asteroids a year come closer to the Earth than the moon’s distance of 240,000 miles. 90% of the larger ones, ranging from mountain-size on up, are already known thanks to detailed surveys with both ground-based and orbiting telescopes. The tally stands at around 910 for the moment. 2012 BX34 ranks 15th on the list of closest approaching asteroids. Below are the top ten as of January 27, 2012 along with their distances at the time of closest approach to Earth:
1. 2011 CQ1 – 3,405 miles on Feb. 4, 2011
2. 2008 TS26 – 3,821 miles Oct. 9, 2008
3. 2004 FU162 – 4,060 miles March 31, 2004
4. 2011 MD – 7,500 miles June 27, 2011
5. 2009 VA – 8,699 miles Nov. 6, 2009
6. 2008 US – 15,534 miles Oct. 20, 2008
7. 2004 YD5 – 20,000 miles Dec. 19, 2004
8. 2010 WA – 24,000 miles Nov. 17, 2010
9. 2011 CF22 – 24,000 miles on Feb. 6, 2011
10. 2008 VM – 29,760 miles on Nov. 3, 2008
The list is interesting because the closest approaches have all been within the past few years. Are we suddenly being buzzed by more asteroids? No. What you’re seeing is a selection effect due to improvements in equipment, cameras and deliberate surveys to hunt for Earth-approaching asteroids that might pose a threat to Earth now or in the distant future. It’s a little like hunting for blueberries in the forest. After you find the first patch and get familiar with the look of the leaves and habit of the plant, you suddenly start seeing blueberries everywhere.