Zippy Little Asteroid 2012 BX34 Makes A Quick Visit

Funny how linear things are in Orion's Belt and Sword. This 21-minute long time exposure with a 120mm lens shows the trails of the three Belt stars at top and the Sword. The slightly fuzzy trail of the Orion Nebula is the middle stripe near bottom. Photo: Bob King

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.

The Milky Way last night around 10 o'clock. Sirius is at bottom; Orion with his 3-starred Belt and Sword dangling below is at right. Details: 15mm lens at f/2.8, ISO 3200 and 30 second exposure. Photo: Bob King

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.

Asteroid 2012 BX34 is the faint streak to the right of the top star in this 2-minute time exposure photo taken early this morning. Credit: Ernesto Guido, Giovanni Sostero & Nick Howes

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.

6 Responses

  1. Timothy Fleming

    I am new to night sky viewing. In your sky photo, is that Castor and Pollux on the extreme upper left? I live in St. Louis.


      1. Tim Fleming

        Hi Bob,
        A clear winter night provides very nice viewing. I am out about 20 miles SW of the city and not completely light polluted – but unable to see the Milky Way. One of these weekends I am taking my daughter out in a more rural area to enjoy the sight of the Milky Way.


        1. astrobob

          South’s a good direction to go, since so many celestial objects are in the southern sky. I bet your daughter will be amazed at how many stars she’ll see when you take her out for a Milky Way view.

  2. Just a quick question. On the list of closest approaching asteroids I only see asteroids that were spotted after the year 2000. Does the list only contain asteroids that were spotted after the year 2000, or is it a complete list of all times? If this would be the case we should be warned since activitiy of near to earth asteroids would be very high over the last 11 years.

    1. astrobob

      Great question. These are the closest approaches to date, not just the past 11 years or so. I didn’t include a couple others like Apophis that will be making close approaches in the future. Most if not all of the asteroids on the list are tiny like 2012 BX34 and their close approaches are recent, because we’re simply getting better at finding these extremely faint objects. Part of the reason are technology improvements like very sensitive electronic cameras and part thanks to deliberate surveys using ground-based and orbiting telescopes. Only in the past few decades have we become aware that near-Earth asteroids can pose a threat to our planet, so funding has been made available to special surveys to hunt for them. There’s no question that asteroids were flying near Earth in, say, the 1940s or 1950s, but we lacked the equipment to spot these tiny, extremely faint objects. Eros, a near-Earth asteroid, was discovered in 1898, but it’s relatively bright. The closest approach it made in 20th century was 22 million miles – much too far to make a top ten list. I hope this helps to answer your question.

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