The Lemon Fool

Asteroid apophis, nearly 400m in diameter, will pass earth in 10 years at a distance of just about 31.000km, which is closer than some satellites and will be the closest asteroid in recorded history and possibly in your lifetime.



99942 Apophis (/əˈpɒfɪs/, previously known by its provisional designation 2004 MN4) is a 370-meter diameter near-Earth asteroid that caused a brief period of concern in December 2004 because initial observations indicated a probability of up to 2.7% that it would hit Earth on April 13, 2029. Additional observations provided improved predictions that eliminated the possibility of an impact on Earth or the Moon in 2029.

However, until 2006, a possibility remained that during the 2029 close encounter with Earth, Apophis would pass through a gravitational keyhole, a small region no more than about 0.5 mile wide, or 0.8 km that would set up a future impact exactly seven years later on April 13, 2036. This possibility kept it at Level 1 on the Torino impact hazard scale until August 2006, when the probability that Apophis would pass through the keyhole was determined to be very small and Apophis' rating on the Torino scale was lowered to zero.

By 2008, the keyhole had been determined to be less than 1 km wide. During the short time when it had been of greatest concern, Apophis set the record for highest rating on the Torino scale, reaching level 4 on December 27, 2004.

https://en.wikipedia.org/wiki/99942_Apophis

With that much stuff flying around in space, I've often wondered if these types of calculations might always be made null and void by some other non-tracked entity simply hitting the main object in such a way that it would nudge it ever so slightly off course....

I'm sure it'll be fine...

Hey - have a guess what day it is on April 13th, 2029......

Cheers,

Itsallaguess

Begs the question: 31km from what? The centre of the Earth is a complex enough calculation; any other would be ... should I say ... hit-and-miss!

I see Snorvey's got it. 31km from Dover.

UncleEbenezer wrote:Begs the question: 31km from what? The centre of the Earth is a complex enough calculation; any other would be ... should I say ... hit-and-miss!

I see Snorvey's got it. 31km from Dover.

Er, I think it's 31,000km...

(or were you being ironic?)

Scott.

Snorvey wrote:
Hey - have a guess what day it is on April 13th, 2029...

Brexit Day

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and lookout for the millenium bug 31dec 2999 .........................

UncleEbenezer wrote:Begs the question: 31km from what? The centre of the Earth is a complex enough calculation; any other would be ... should I say ... hit-and-miss!

I see Snorvey's got it. 31km from Dover.

If it really was 31km rather than 31 thousand km then I'd be somewhat more worried

Itsallaguess wrote:With that much stuff flying around in space, I've often wondered if these types of calculations might always be made null and void by some other non-tracked entity simply hitting the main object in such a way that it would nudge it ever so slightly off course....

Since Geostationary orbit is at 35,786km above the equator there might be a chance of it hitting a satellite in that or some other orbit if we were particularly unlucky.

ursaminortaur wrote:

UncleEbenezer wrote:Begs the question: 31km from what? The centre of the Earth is a complex enough calculation; any other would be ... should I say ... hit-and-miss!

I see Snorvey's got it. 31km from Dover.

If it really was 31km rather than 31 thousand km then I'd be somewhat more worried

Itsallaguess wrote:With that much stuff flying around in space, I've often wondered if these types of calculations might always be made null and void by some other non-tracked entity simply hitting the main object in such a way that it would nudge it ever so slightly off course....

Since Geostationary orbit is at 35,786km above the equator there might be a chance of it hitting a satellite in that or some other orbit if we were particularly unlucky.

Just to add if Apophis were to hit a satellite then given Apophis' mass and speed its deflection would probably be fairly minor it would be more likely that the satellite (or a large number of pieces of satellite) would be deorbited and crash to earth.

ursaminortaur wrote:Just to add if Apophis were to hit a satellite then given Apophis' mass and speed its deflection would probably be fairly minor it would be more likely that the satellite (or a large number of pieces of satellite) would be deorbited and crash to earth.

After such a collision, the pieces would be dust sized.

sunnyjoe wrote:

ursaminortaur wrote:Just to add if Apophis were to hit a satellite then given Apophis' mass and speed its deflection would probably be fairly minor it would be more likely that the satellite (or a large number of pieces of satellite) would be deorbited and crash to earth.

After such a collision, the pieces would be dust sized.

Surely it would depend whether it was a head-on collision or a glancing blow ?

ursaminortaur wrote:

sunnyjoe wrote:After such a collision, the pieces would be dust sized.

Surely it would depend whether it was a head-on collision or a glancing blow ?

A 60 million tonne object hitting a satellite isn't going to be much of a glancing blow.

Scott.

swill453 wrote:A 60 million tonne object hitting a satellite isn't going to be much of a glancing blow.

Scott.

Consider also that the impact velocity will be several thousand metres per second

swill453 wrote:

ursaminortaur wrote:

sunnyjoe wrote:After such a collision, the pieces would be dust sized.

Surely it would depend whether it was a head-on collision or a glancing blow ?

A 60 million tonne object hitting a satellite isn't going to be much of a glancing blow.

Scott.

If it hits the edge of the satellite then the bit hit may well be totally destroyed but the rest of the satellite won't be. The shock transmitted through the satellite would likely make the surviving part break up but it is unlikely that it would be shattered into dust sized particles.

ursaminortaur wrote:

swill453 wrote:

ursaminortaur wrote:
Surely it would depend whether it was a head-on collision or a glancing blow ?

A 60 million tonne object hitting a satellite isn't going to be much of a glancing blow.

Scott.

If it hits the edge of the satellite then the bit hit may well be totally destroyed but the rest of the satellite won't be. The shock transmitted through the satellite would likely make the surviving part break up but it is unlikely that it would be shattered into dust sized particles.

Asteroid diameter 370m. So 107,466 m2 projected area.

Larger geostationary satellite, maybe Intelsat-18 using StarBus platform, main portion approx 2m x 2m max. So say 4 m2 projected area.

Assume anything that hits more than 1m of the satellite is a direct hit. A quick calculation suggests that 99% of all the possible ways of these two impacting would be direct hits. To be honest if the overlap were even 0.1m I think that at these velocities the result would be nigh-on vaporisation of the satellite. Given the mass disparity any orbital change to the asteroid would be imperceptible.

regards, dspp