Close shave with an asteroid (8 Sep 2014)

[hebdomad]

An Asteroid ( 2014RC ) just past above Geostationary orbit above New Zealand...

Luckily the 70,000 tonne asteroid, travelling at 10km per second did not hit anything...

http://www.abc.net.au/news/2014-09-08/earths-close-shave-with-an-asteroid/5726692

[Streetwind]

Bit of extra information: the object was no larger than 20 meters across. It has since been removed from NASA's impact risk table, where it held a threat level of 0 on the 10-point Torino scale and a probability of less than 0.0001% to impact Earth at any time in the next 100 years. However, Nicaragua claims that a meteorite hit in the wilderness near the international airport and created a 12-meter crater there last night, and that it's possible that it may have been a splinter from 2014 RC (this is not unusual). Investigation is ongoing.

[KerikBalm]

http://www.purdue.edu/impactearth/

I used their pulldown list, and selected dense rock (1.5 metric tons per cubic meter).

You said 70,000 tons, so assuming a perfect sphere, that means about 45 meter diameter to get to 70 tons with that density.

I assumed more than a glancing blow.... 45 degree angle.

The lowest velocity allowed was 11 km/s, although if the asteroid was going 10km/sec, I don't know how much faster it would be going relative ot earth if it actually hit us.

Anyway:

The projectile begins to breakup at an altitude of 65500 meters = 215000 ft

The projectile bursts into a cloud of fragments at an altitude of 14900 meters = 48900 ft.

The residual velocity of the projectile fragments after the burst is 4.26 km/s = 2.65 miles/s.

The energy of the airburst is 3.68 x 10^15 Joules = 0.88 x 10^0 MegaTons.

No crater is formed, although large fragments may strike the surface.

Energy before atmospheric entry: 4.33 x 10^15 Joules = 1.03 MegaTons TNT

The average interval between impacts of this size somewhere on Earth is 342.4 years

The air blast will arrive approximately 25.3 minutes after impact.

Peak Overpressure: 6.13 Pa = 6.13E-05 bars = 0.000871 psi

Max wind velocity: 0.0145 m/s = 0.0323 mph

Sound Intensity: 16 dB (Barely Audible)

I said it had an impact in 500m deep water 1000 km from shore:

Tsunami wave amplitude is less than 10 cm at your location.

Doesn't sound like we'd have cared much if it hit - we might have gotten some fragments that yielded good science points.

Darn!

[Streetwind]

Dunno where the 70 kt mass figure comes from. None of the sources I can find, such as JPL and the IAU, make any sort of mention regarding to mass. However, they all agree that the object is estimated 20 meters in size, +/- 10 meters at most.

They also compare it to the Chelyabinsk meteor, which is believed to have been roughly the same size, also about 20 meters, with up to 13,000 metric tons in mass (not 70,000). Said meteor airburst 30 kilometers up and released an energy of about 0.5 megatons, injuring some 1,500 people and damaging over 7,200 buildings with its shockwave, according to wikipedia. The burst was both very visible and very audible.

[hebdomad]

The 70,000 ton figure was from the Swinburne University Facebook page. I think the 13,000 ton figure is more realistic... That said, has anyone being able to calculate the mass of these rocks yet?

Edited September 9, 2014 by hebdomad

[KerbMav]

Bit of extra information: the object was no larger than 20 meters across. It has since been removed from NASA's impact risk table, where it held a threat level of 0 on the 10-point Torino scale and a probability of less than 0.0001% to impact Earth at any time in the next 100 years. However, Nicaragua claims that a meteorite hit in the wilderness near the international airport and created a 12-meter crater there last night, and that it's possible that it may have been a splinter from 2014 RC (this is not unusual). Investigation is ongoing.

http://www.bbc.com/news/world-latin-america-29106843

[Streetwind]

Nicaragua officials remain extremely convinced, while other parties expressed doubts:

http://www.space.com/27071-nicaragua-meteorite-crater-impact-video.html

[Jesrad]

Chances are the Nicaragua people heard a sonic boom from some military aircraft that evening, then later found a fresh hole somewhere to blame it on.

[lajoswinkler]

That hole doesn't look as it has been caused by this fragment. It looks like a scaled down version of something more serious. Small fragments bursting above ground would leave wide, shallow craters, if any. Probably no crater at all, just burned area.

This looks like someone has put few sticks of dinamite in the ground.