Celestia Forums

OK, perhaps a little dramatic , but there was a near miss in Canterbury, New Zealand this afternoon (around 03:00 GMT).

The house shook from a huge sonic boom and air blast. This was apparently heard over a 100km radius or more.
Current speculation in the news is that it was a baseball sized or up to 1m sized meteor/bolide or piece of space junk.
Nothing found on the ground yet, and apparently came in at quite a low angle so may have bounced off the atmosphere or exploded at maybe 10km height.

Darn it! Why do I always miss out on the fun? lol

More:
http://news.bbc.co.uk/2/hi/asia-pacific/5337788.stm

"It started off with a little boom then a real massive boom. And I mean massive - like the daddy of all booms"

hmm if it just burned in the atmosphere up why the big boom? shouldn't that result in a short but constant loud noise?
and by just breaking the sound-barrier I doubt it could shake half of new zealand...

so in my amateur opinion it was more likely to hit the ground somewhere at a very high speed.

phoenix wrote:

"It started off with a little boom then a real massive boom. And I mean massive - like the daddy of all booms"

hmm if it just burned in the atmosphere up why the big boom? shouldn't that result in a short but constant loud noise?
and by just breaking the sound-barrier I doubt it could shake half of new zealand...

Given how fast it's going and how rapidly it's decelerating in the atmosphere that's not very unlikely. My guess is that the little boom might have been when it was higher up and the larger one might have been it breaking the sound barrier closer to the ground (so it sounds louder). I think that each time it breaks a multiple of the sound barrier you'd hear another boom.

Depending on the angle it's coming in at, it's quite possible for a large area underneath it to be able to hear the booms. And those can shake things up quite a bit (witness how windows can shatter if a jet flies by close overhead and breaks the sound barrier).

so in my amateur opinion it was more likely to hit the ground somewhere at a very high speed.

That wouldn't shake things up much - the thing was only the size of a baseball or basketball after all. It'd make a hole a few metres wide in the ground possibly, but that's about it.

Malenfant wrote:Given how fast it's going and how rapidly it's decelerating in the atmosphere that's not very unlikely. My guess is that the little boom might have been when it was higher up and the larger one might have been it breaking the sound barrier closer to the ground (so it sounds louder). I think that each time it breaks a multiple of the sound barrier you'd hear another boom.

now that i did some research on the sound-barrier i found out that the noise greatly increases with the velocity of the object breaking it

but that could only happen when the comet enters the atmosphere where the air becomes thick enough to create such a shockwave...
at this altitude it must be a pretty big shockwave to reach earth and cover half of new zealand so this little meteorite wasn't so little at all


or am I missing something here?

It's all about energy. As in any impact kinetic energy is converted to heat, light, and sound, as well as other kinetic energy (air movement). To an object travelling at say 50km/sec, hitting something as dense as the earth's atmosphere is not much different to hitting a solid object.

Personally, I only heard the one boom (I was inside) which sounded something like either a huge thunderclap, or as I'd imagine an LPG tank explosion would sound.

What I found interesting was the single huge gust of wind (perhaps 100km/h) which shook the house at the same time. This I imagine was the compressed air front responsible for the "sonic boom".

Let's say it was 1m in diameter, it might weigh say 1 tonne. At 50km/sec, that's 5 x 10e7 kg.m/s.
Depending on surface area, attitude, and angle of attack, that could move a lot of air I guess.

BTW. Saw on tonight's news that a fragment (Not confirmed as genuine yet) about 100mm in size has been found in a farm field, but is apparently a little light (in weight) to be asteroidal.

My theory is that the Space Shuttle astronauts flushed the toilet and what we should be looking for is a frozen block of ****. (On this note Selden, you'll probably want to move the thread to purgatory )