Category Archives: meteors

bolides, meteors

Stuff Hits Earth: News at 11

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Fireball Over Sweden

Meteor Fireball in Sweden (Courtesy www.meteoritesusa.com)
Meteor Fireball in Sweden (Courtesy www.meteoritesusa.com, http://nachrichten.t-online.de/c/17/40/62/72/17406272.html, and sydsvenskan.se))

Last night (January 17) a fireball lit up the skies over Malmö, Sweden and was seen by people in Germany and the Netherlands. You can see a security camera view of the event here. It looks pretty spectacular and no doubt anybody who saw it was probably quite surprised and shocked.

Now the object at the heart of this fireball was probably a chunk of rock that broke up and scattered its pieces to the ground as it blasted through our atmosphere. There aren’t (yet) any reports of damage, and I imagine meteorite hunters will be swarming around suspected impact sites to gather evidence.

Stuff coming in from space is a pretty common occurrence on our planet. Most of it is dust-particle-sized or maybe the size of peas, and those pieces tend to burn up high above the surface and leave behind glowing trails. That’s usually what we see during a meteor storm.

Speaking in general terms, larger stuff (rock-sized and a bit larger) creates bolides, like the one that flared over Sweden last night.  Most of the time these just break up and scatter out, leaving behind lots of cool smaller rocks for meteorite hunters to collect.

The largest material is what scientists worry about — those are typically tens of meters across and larger.  That’s not what Swedes and others saw last night. I’m taking about things the size of houses or small mountains can do some real damage to Earth’s surface, including gouging out craters and  slamming into populated areas. In the worst-case scenarios — like impacts of objects at least 1 kilometer across and larger — those actions could disrupt the atmosphere and perturb our global climate.  One of these large impactors could create so much damage that global temperatures could plunge, leading to crop damage and destruction, and societal breakdowns. According to the folks at NASA’s Ames Research Center Impact group (led by astronomer David Morrison), studies have been done that suggest that the minimum mass of an impacting body that would produce global consequences is several tens of billions of tons. An object with that much mass would set off a groundburst explosion with enough energy to equal a million megatons of TNT. The only thing worse than that would be nuclear war (unless we had several hits of that size).

Compared to that, last night’s bolide is a mere “plinker”.

Thanks to Daniel Fischer of Cosmos4U and the Cosmic Mirror for passing along news of the Sweden bolide.

meteorites, meteors, NEOs, spaceguard survey

Asteroid Piece on Course for Earth

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No Damage Expected and It’s Not a Threat

As reported on Phil Plait’s Bad Astronomy site and through the Minor Planets Center at the Harvard-Smithsonian Center for Astrophysics, an object called 2008 TC3 is going to enter Earth’s atmosphere tonight and burn up over Sudan.  It’s very small–only about 2 meters across–which means that by the time it gets through our atmosphere, only a few small rocks will be left to rain down on the desert (if any of it is left to fall). The entry time, as reported by Steve Chesley of NASA JPL is 2:45 UT October 7 (equivalent to 10:46 p.m. Eastern time in the U.S.).  For folks along the path of entry, it should be a great bolide to watch as it streaks in from space!

So, the amazing thing about this predicted impact is NOT that it is going to occur, although that’s pretty neat. It’s not even that it’s a piece of space rock coming in — although it should be pretty darned spectacular to see!  No, the coolest thing about this whole thing is that this is the first time an incoming asteroid and potential impact has ever been predicted. The sightings of this thing have been coming in from the SpaceGuard Survey over the past half day and they are good enough to predict the time of the object’s entry into our atmosphere. It’s pretty amazing that the survey has been able to spot something this small.

Now, in case you’ve seen some woo-woo reports about this thing, it’s not anything more than an incoming rock from space. There’s lots of them out there, and given enough time, we’re bound to see one or two of this size come in every once in a while.  There’s nothing magical or mystical about it. It’s all quite natural.

Of course, questions are arising about its possible effect on Earth. According to Andrea Milani at the University of Pisa,

“the effect of this atmospheric impact will be the release, in either a single shot or maybe a sequence of explosions, of about 1 kiloton of energy. This means that the damage on the ground is expected to be zero. The location of these explosions is not easy to predict due to the  atmospheric braking effects. The only concern is that they might be  interpreted as something else, that is man-made explosions. Thus in  this case, the earlier the public worldwide is aware that this is a  natural phenomenon, which involves no risk, the better.”

Folks who track these things for a living are hoping that scientists will be able to mobilize some spectrographs and cameras to do some in-depth studies of the object as it comes in.  Such studies will help astronomers figure out the shape and chemical composition of the naturally occurring rocks it was made of, and help determine where it first formed in the solar system some 4.5 billion years ago.

The meteor should be visible from eastern Africa. It will likely appear as an extremely bright fireball traveling rapidly across the sky from northeast to southwest. It should enter the atmosphere over northern Sudan at a shallow angle.

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