Saturday, February 16, 2013

What an exciting day



Well that was quite a coincidence.  Though we should consider this, if coincidences never occurred, that in itself would be a coincidence. 

At 3:30 UT yesterday (9:30 local time) we had the Russian meteor (top two photos).  And 16 hours later at 19:30 UT, we had the asteroid flyby (diagramme). The two events were each historic and entirely unrelated. The first was unexpected, the second accurately predicted. I'll start with three links for the Russian meteor:

     UT = Universal Time, the same as Greenwich Mean Time  

The asteroid flyby

I recommend this NASA broadcast which includes an interview with scientist Paul Chados explaining the similarities and differences between the two events.  He's from NASA’s Near Earth Object Program Office. “What an exciting day” he enthuses, “it's like a shooting gallery here, we have two rare events of Near Earth Objects approaching the Earth on the same day …”

Asteroid 2012 DA14 came nearer to the Earth yesterday than many communications satellites, which inhabit the geosynchronous ring shown in the diagramme above. (That's the orbit communications satellites use in order to appear stationary with respect to the Earth.)   At 45 metres wide, the space rock is the biggest ever observed object to swoop this close to Earth. Had it collided with the planet, it would have caused devastation akin to the 1908 Tunguska event that flattened 2000 square kilometres of trees in Siberia (photo bottom right).

Astronomers discovered DA14 a year ago and it's on an orbit round the Sun very close to the Earth’s. What's spooky to me is that for all we know it has been on this orbit since forever without anyone knowing until last year.

More about the Russian meteor

Russian officials put the number of people injured at almost 1,200, but seemingly only around 40 were taken to hospital (?), mostly as a result of flying glass shattered by the sonic boom created by the meteorite's descent, as people were drawn to their windows by the sound of explosions as the meteorite plunged to Earth in a series of fireballs just after sunrise. "There was a big explosion and then a series of little explosions. My first thought was that it was a plane crash" said one witness. There were no reported deaths.

The meteorite is thought to be 15m (about 48 feet) across, that’s one third the size of DA14. It entered the atmosphere travelling at a speed of at least 33,000 mph and broke up into chunks between 18 and 32 miles above the ground.

The event caused panic in Chelyabinsk, a city of more than 1 million people to the south of Russia's Ural mountains, as mobile phone networks swiftly became jammed by the volume of calls. The vapour trail was visible for hundreds of miles around.

Amateur video footage from the area showed the chunks of meteorite glowing more brightly as they approached the moment of impact.

Sources for Russian meteor: Guardian website yesterday, Russian Academy of Sciences (reported by Guardian) and Paul Chados of NASA.


3 comments:

  1. What is the geosynchronous ring? Do we know the composition of the Russian meteor? How similar to, or different from, DA14 was it? Did it have a sun-orbiting path, or was it just flying through space on its own path?

    It is quite something to think that there could be an unknown catastrophic asteroid out there just a year away from crashing into my house.

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  2. Have updated post re geosynchronous ring.
    For composition of the Russian meteorite we await the findings of Russian scientists who will be looking for the fragments now and analysing them. Often they consist of iron. Meteorites are unpredictable, most originate in the Asteroid Belt, between the orbits of Mars and Jupiter. Some are bits of rock from Mars or the Moon or somewhere, blown off by a meteorite impact. The Russian meteorite was totally unexpected, so nobody knows where it came from, but it will doubtless have be in a Sun-orbiting path of some sort. Perhaps once its composition is analysed an informed guess can be hazarded.
    I doubt much is known about the composition of DA14 yet, maybe one day a probe will be despatched to have a look.

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