More precise numbers on 2004MN4 asteroid flyby in 2029

[marcus]

http://science.nasa.gov/headlines/y2005/13may_2004mn4.htm?list45222

apparently they've crunched more numbers and can say that the asteroid will pass Earth at altitude of some 30,000 km
shining like a 3rd magnitude star

If I understand correctly, we are being told that it will pass Earth at a distance roughly like that of a geosynchronous communication satellite.

it is about 320 meters wide, so if you are in the part of europe, asia, africa where it is visible you might see it when it passes. the article says visible even where there are city lights

I don't know how much of this new, or how reliable it is. It is a lot more definite than back in 2004 when they were thinking it might run into the Earth and estimates seemed to change daily

 

[Chronos]

I thought they had since backed off that 30k distance, but it's true the estimates have frequently and presumably will continue to change over the next 20+ years. It is very difficult to predict long term orbits of these little rogues. I will be quite nervous if they are still saying 30k in 2028... assuming I'm still lucid.

 

[tony873004]

Here's an illustration of the latest trajectory.

http://orbitsimulator.com/orbiter/2004mn4may.GIF

I threw this together with data from JPL Horizons. It looks like it did get notched slightly closer in recent weeks. According to JPL, the latest data is a solution generated on May 6, 2005. The double purple line in the image is February's prediction and the May 6 prediction. Approaching Earth, they are virtually identical. After Earth passage, they split apart slightly.

I don't think they're going to change that much between now and 2029. Just a little more of the same of what you see in the image between the Feb prediction and the May prediction. I think they're comfortable that the error bar does not include Earth even though the asteroid's close approach point is only about 30,000 km. When the predicted pass was at abou6 60,000, they were giving it a 1/32 chance of striking. Then, without changing the 60,000 estimate by much they lowered it to something like 1 in 40,000. Then a month later, they moved the close passage point twice as close, to about 30,000, but still maintained the 1 in 40,000 chance of a strike.

I just took this to mean that in December it was 1 in 32 with a really large error bar, then they shrank the error bar enough to exclude Earth, but not the 30,000 km point. Then, in January, they shifted the predicted passage to about 30,000 which was still in the fat part of the error bar of the 60,000 km point. In January, they actually bounced radar off it. That's when they shoved it a little closer, and shrank the error bar as well.