Apophis will make another relatively close approach in 2012-2013. At that point (if not sooner), they should be able to forcecast whether it has ANY chance of hitting the keyhole. If they cannot rule the possibility out at that point, NASA has talked of sending of probe to land on Apophis to continuously transmit its location. That should mean that well before 2029 we should know if Apophis will hit the keyhole and divert it BEFORE 2029 to prevent it from going through the keyhole.

At present, Apophis between the Sun and Earth, making it very difficult to track. Its orbit is very similar to Earth's and it travels only slightly faster (the orbit is also more elliptical than Earth's).

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Keeper of the Jabberwock

What about the moon? It's big and dense enough to crash into the moon and alter it's course, possibly resulting in a bigger disaster if the Earth is in the way of its altered course, this would also be very unlikely but probably wouldn't global destruction due to lack of velocity. The only concern i have with the moons part in all this is that its gravity may swing the asteroid into the Earth whilst increasing its velosity.
Suppose the moon was so obvious that it didn't cross your mind.

Mass of Apophis = 2×10^10 kg
Mass of Moon = 7.383 × 10^22 kg
Thus the mass of the Moon is on the order of 4 trillion times that of the asteroid. Orders of magnitude greater than the difference between a fully loaded semi and a mosquito. Apophis is not nearly big enough to significantly alter the orbit of the Moon, but it would be a pretty good light show.

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Any day you wake up on "the right side of the dirt" is a good day.

T. Anderson

But note that there's no need to worry about it hitting the Moon, because it has to be at least 20 times more likely to hit the Earth, and that would be something we'd care a lot more about anyway! (Question: what is the "keyhole", and is this a real idea or a make believe one?)

"Keyhole" has referred to a target region in space at least since Apollo. In that case hitting the keyhole at a certain distance from earth meant the reentry trajectory would intercept the earth's atmosphere at the correct angle for safe return. Don't know if the term was used in a space navigation context before then. It's also been used to describe the target region required for an unmanned probe to execute a maneuver, say a planetary flyby.

The trajectory of all bodies in space is perturbed by effects sunlight, radiation, outgassing, other bodies, etc. Those affects can be quantified to a fairly high degree, depending on how much data is available.

After all those effects are calculated to the available accuracy, there remains an uncertainty since we don't have absolute accuracy in measurement or perfect data about the deep space environment or the object. I think the term is "trajectory dispersions".

I think "keyhole" refers to a 2D region in the trajectory path which if intersected would result in the object hitting a certain target, even if the normal perturbations -- all dispersions -- happened.

I think the keyhole size varies depending on object distance from target. The farther away from target, the larger the keyhole is. In this sense, there's not one keyhole, but many, depending on the distance to target.

The keyhole also isn't a fixed size based on physical laws, but a navigation construct based on available data. IOW higher accuracy data (more observations, better software, etc) could shrink the size of a keyhole, even though nothing physical changed in space or the body.

Don't know what the etymology is -- whether the physical region has a keyhole shape if plotted or if it simply came from "looking through a keyhole" as defining a narrow trajectory angle.

If someone has more information, please correct me.

I think it´s just a metaphor for a hole. this article says it is only 2,000 ft in diameter.

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What brings us together is stronger than what pulls us apart

I was just checking today on the list of close approaches and now both 2032 and 2036 are at Torino 0. New calculations made in the last weeks?

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The impossible often has a kind of integrity which the merely improbable lacks.

Wouldn't the keyhole have to be smaller the farther away from the target, not larger?

clop

Sure shows where our priorities are as a nation...

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Jami Cat
Astronomy is looking up... :)

Yes, I got it backward. Thanks for the correction.

...and we spend half of NASA's annual budget in Iraq every month!

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Any day you wake up on "the right side of the dirt" is a good day.

T. Anderson

Anyone know how close Apophis will get in 2013 and 2021? Also, what magnitude will it reach during those approaches?

In 2013, 14.5 Gm in January and 36.4 Gm in July.
In 2021, 16.9 Gm
don't know the magnitudes.

edit: actually, I found them. Put the mag from JPL in my Solex9.0.
15.5 for the January 2013 approach, and 15.4 in 2021

Hum,
if you do a forum search for "Apophis" or "2004 MN4" or "Killer asteroid" , "not again" or "death from the sky" etc, there will be no doubt a predicted forecast; but, i would guess that it would be visible to the naked eye as a mag 3 - 4 moving star during the 2029 encounter, (and in the worst case scenario as a growing ball of light brighter than the sun).

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`Irony` actually does mean `metal like`...