COSMIC EVENTS

YESTERDAY, SATURDAY, March 9, 2013, had yet another asteroid flyby, this one called 2013 ET, the size of a football-field. On February 15, we had one of record-breaking closeness—only to have a completely different one injuring 1000 people, for goodness sake.

And then there was Tunguska in 1908—and Yucatan in 66 million B.C.

First, some terminology: An asteroid is a micro planet. There’s a whole belt of them wandering between Mars and Jupiter; i.e., in our neighborhood of the solar system.

A meteoroid is a small piece of comet (icy dust) or asteroid. If it enters our atmosphere and light up, it’s a meteor or “shooting star.’

Last, any fragments surviving this fiery entry and landing on Earth are called meteorites.

We’ve had them all within the past couple weeks (including comet Pan-STARRS visible now until the end of March).

Yesterday’s event was Meteor 2013 ET doing a distant flyby, 604,500 miles away. This is about 2 1/2 times the distance from Earth to the moon. Meteor 2013 ET is about the size of a city block, so let’s be thankful it was that far away. Check out www.slooh.com and www.virtualtelescope.eu to see their images.

Back on February 15, 2013, Meteor 2012 DA₁₄ had a much closer flyby at 19:37 GMT. (Pacific Time is GMT-8 for Standard; GMT-7 for Daylight Savings.) This meteor was around 100 ft. in diameter and set a record for closeness in class, at 17,239 miles from Earth, closer than the orbits of geosynchronous satellites. No worry, though: The nearest it ever got to any satellite was 1200 miles.

This 40,000-ton solar orbiter was discovered in February 23, 2012 (hence its family name). It’ll return in 2046 but at about twice the distance of yesterday’s 2013 ET. People around on February 16, 2123, will have Meteor 2012 DA₁₄ skim by at around 19,000 miles; close, but no cigar.

But back to our February 15: Completely unrelated to Meteor 2012 DA₁₄, another object of about 55 ft. across and 10,000 tons entered the atmosphere.

Chelyabinsk Event, February 15, 2013. Image from The Washington Post.

This was over Chelyabinsk, Russia, at 3:20 GMT (just 16 hours before 2012 DA₁₄’s flyby). This meteor was initially travelling around 40,000 mph. At about 60,000 ft. it exploded with the force of 500 kilotons—about 30 times that destroying Hiroshima. The airblast broke windows and other structures; more than 1000 people were injured, mostly by flying glass.

The vastness of Russia has had two significant meteor events in a bit more than 100 years. Original image from www.utexas.edu.

Russian scientists identified its meteorites as Chondrite, a primitive asteroid material. Others, however, put a different spin on matters.

This just in. Image from Carl of Jerusalem.

But wait; there’s more. On June 30, 1908, at 00:14 GMT (or the equivalent of GMT used back then), an object of about 330-ft. diameter exploded at perhaps 20,000 ft. above Tunguska, Siberia.

Trees were flattened for more than 830 sq. mi. by the Tunguska Event.

The blast has been estimated at 1000 times that of Hiroshima’s. It destroyed 80 million trees over 830 sq. miles and was the largest meteor strike in recorded history, equivalent to a Richter 5.0 earthquake.

Here are estimates of airbursts derived from the “Earth Impact Effects Program,” Imperial College London/Purdue University (http://impact.ese.ic.ac.uk/ImpactEffects).

Last, the Yucatan Event, circa 66 million years ago, destroyed much of the life on Earth. It’s estimated this meteor had a 6.2-mile diameter and delivered a blast more than two million times anything created by man.

Yucatan Event, circa 66 million years ago. Image from www.earlham.edu.

Shock waves triggered earthquakes and volcanos. Tsunamis of 6000 ft. occurred. Particles covered the Earth and destabilized the climate for years.

To help you sleep tonight, be aware that there is a Minor Planet Center, a branch of the International Astronomical Union, that keeps an eye on this. ds

© Dennis Simanaitis, SimanaitisSays.com, 2013