Celestia Forums

Friends...

Have just posted an interesting add-on on the Motherlode page located HERE.
Please notice that the asteroid depicted in this add-on was discovered on November 3rd, 2008.

The very interesting thing about this add-on is its close proximity to our favorite planet.

This small 3m asteroid was at its closest approach on November 4th, at 14:34:00 PST over Antarctica at 42,325 km away.

Does this arouse any angst from any other Celestia users? The thing was discovered only 1 day before it arrived at its
closest approach to our planet. What would have happened had it been headed directly into the Earth?

Very interesting, and points out how far we still have to go in order to be adequately forewarned about any
other such future events. Many thanks to Philp for the add-on. Got my mind thinking about future possibilities.

Thanks, Brain-Dead

BobHegwood wrote:Does this arouse any angst from any other Celestia users? The thing was discovered only 1 day before it arrived at its
closest approach to our planet. What would have happened had it been headed directly into the Earth?

It would have disintegrated harmlessly in Earth's atmosphere, just like the similarly sized asteroid 2008 TC3 did.

--Chris

chris wrote:It would have disintegrated harmlessly in Earth's atmosphere, just like the similarly sized asteroid 2008 TC3 did.

Yes, I understand this from the descriptions I received while searching the web.
However, my point was due to the fact that this object was not even discovered until
the day before it arrived.

Sorry, but that really does cause me some concern. Is this simply because of its size? Or,
is due to the direction of the approach? Just curious to know why something headed our way
would not have been spotted earlier. I (perhaps mistakenly) thought that there were
outposts around the world which are dedicated to precisely this kind of detection.

No?

Thanks, Bob

--- edit ---

3m is pretty darn small. It doesn't surprise me it was only one day. Hell, it surprises me they saw the thing at all.

Johaen wrote:3m is pretty darn small. It doesn't surprise me it was only one day. Hell, it surprises me they saw the thing at all.

Okay then, since I obviously know nothing about these things.
What sized asteroid should we worry about? Assuming that it's composition is
hard enough to worry about too.

Please excuse the ignorant question, but I really am curious now.

BobHegwood wrote:

Johaen wrote:What sized asteroid should we worry about?
Assuming that it's composition is hard enough to worry about too.

Bob, if you wish to see what could happen with any kind of object hitting the Earth at given size, density, speed, angle and target geological characteristics, give a look here:
http://www.lpl.arizona.edu/impacteffects/
If you read the "tell me more" at the bottom page, you'll see that the authors' approach looks scientifically correct so.... just to play a little.
Taking as example the 2008VM asteroid, whose you are speaking of, here the results (with most of input data taken as average):

Your Inputs:
Distance from Impact: 1.00 km = 0.62 miles
Projectile Diameter: 3.00 m = 9.84 ft = 0.00 miles
Projectile Density: 3000 kg/m3
Impact Velocity: 17.00 km/s = 10.56 miles/s
Impact Angle: 45 degrees
Target Density: 2500 kg/m3
Target Type: Sedimentary Rock

Energy:
Energy before atmospheric entry: 6.13 x 1012 Joules = 0.15 x 10-2 MegaTons TNT
The average interval between impacts of this size somewhere on Earth is 0.7 years

Atmospheric Entry:
The projectile begins to breakup at an altitude of 54000 meters = 177000 ft
The projectile bursts into a cloud of fragments at an altitude of 42600 meters = 140000 ft
The residual velocity of the projectile fragments after the burst is 14.8 km/s = 9.18 miles/s
The energy of the airburst is 1.50 x 1012 Joules = 0.36 x 10-3 MegaTons.
No crater is formed, although large fragments may strike the surface.

Major Global Changes:
The Earth is not strongly disturbed by the impact and loses negligible mass.
The impact does not make a noticeable change in the Earth's rotation period or the tilt of its axis.
The impact does not shift the Earth's orbit noticeably.

Air Blast:
The air blast at this location would not be noticed. (The overpressure is less than 1 Pa)

Enjoy.
Bye

Andrea

--- edit ---

ANDREA wrote:Bob, if you wish to see what could happen with any kind of object hitting the Earth at given size, density, speed, angle and target geological characteristics, give a look here:
http://www.lpl.arizona.edu/impacteffects/
If you read the "tell me more" at the bottom page, you'll see that the authors' approach looks scientifically correct so.... just to play a little.

Hey, thanks very much for that link Andrea. Very cool.
I'll calm down now since you've given me the resources I need to understand
when I should be worried.

Thanks again, Brain-Dead

--- edit ---

BobHegwood wrote:

ANDREA wrote:Bob, if you wish to see what could happen with any kind of object hitting the Earth at given size, density, speed, angle and target geological characteristics, give a look here:
http://www.lpl.arizona.edu/impacteffects/
If you read the "tell me more" at the bottom page, you'll see that the authors' approach looks scientifically correct so.... just to play a little.

Hey, thanks very much for that link Andrea. Very cool.
I'll calm down now since you've given me the resources I need to understand
when I should be worried.
Thanks again, Brain-Dead

You are always very welcome, Bob, happy you like it.
Bye

Andrea

john Van Vliet wrote:i would not worry , to much,about anything smaller than 25M ( Arizona-- Meteor Crater NP was a rock about 45M )

John, I don't agree, I think all is relative.
I mean that even an object smaller than this one:
http://six.pairlist.net/pipermail/meteorite-list/2004-December/005905.html
should be highly worried by a single, because it can easily kill a person (this woman was very lucky, indeed!).
But if we consider a wider environment, e.g. a small town, well, a piece of rrock much smaller than Arizona crater's one could totally eliminate it from the Earth surface.
For a big town, we should fear a 0.3-0.5 km wide object, while for a global threat we need at least a 10 km object, like Chicxulub's one.
It's a matter of proportions, evidently.
Personally I remember that during a night-long observation of August's Perseids with some friends, many years ago, I saw a bolid that was falling straigh toward me, no tail, only a very luminous small source, increasing its luminosity in a very very short time, until it disappeared, with a thunder clearly listened by me and my friends.
It was a fearful experience, because that very short time was felt by me as very, very, very long, and I was sure to be hit by the fragments (that, fortunately, didn't reach the ground).
So, men, watch your head and use heavy iron caps, little sky pieces are falling down.
Hehehehehe.
Bye

Andrea

Yeah, I'll side with the "who cares, a 3m object" side.
If they fail to see a 500 metre object until a day after a close, closest approach, then I'll bicker, lol.

BobHegwood wrote:

ANDREA wrote:Bob, if you wish to see what could happen with any kind of object hitting the Earth at given size, density, speed, angle and target geological characteristics, give a look here:
http://www.lpl.arizona.edu/impacteffects/
If you read the "tell me more" at the bottom page, you'll see that the authors' approach looks scientifically correct so.... just to play a little.

Hey, thanks very much for that link Andrea. Very cool.
I'll calm down now since you've given me the resources I need to understand
when I should be worried.

Thanks again, Brain-Dead

I wonder about this forum if a super massive asteroid arrive. Where to place notices, in "Development" since there will be developments about the situation; in "Purgatory", since there will be need of some praiers, or more simply in "Physics and Astronomy" due to the matter.