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Asteroids (Read 146468 times)
shellandtube
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Re: Asteroids
Reply #90 - 11/20/07 at 19:04:27
 
The oracle has spoken.
Cheers tony i think that covers alot of my questions. I read the article understanding alot but not all of it. just goes to show the errors can be huge, a deviation of 1.2km in 2029 can grow to 28600km by 2036 (if i read it right). I never realised how the errors in what we know about about the planets could be so significant, from the table on page 9 it suggests this could be one of the major sources of error.
Very interesting. Cheers again.
 
PS. I would definately be interested in any simulations.
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The shortest distance between two points is a straight line, or is it?
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Tony
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Re: Asteroids
Reply #91 - 11/20/07 at 23:08:02
 
Here is a simulation containing Apophis and the 32 asteroids mentioned in Giorgini, et al.
http://orbitsimulator.com/gravity/simulations/apophis2007.gsim
 
You can run the simulation and record Apophis' closest distance to Earth on April 13, 2036, then run it again, this time deleting all the extra asteroids, and again recording its closest distance on April 13, 2036.  This should give you a clue about how these asteroids contribute to Apophis' trajectory.
 
But if you do this, you must use a slow time step.  I recommend 1 second.  This will take a long time to do.  You'll have to leave the simulation running overnight, and perhaps a few hours more depending on your computer's speed.  It should run a lot faster when you delete the extra asteroids.
 
I'd suggest you use either Auto Save from the file menu, or Save from Autopilot on perhaps April 12, 2036 to make sure you capture the simulation just prior to Earth passage.
 
I have not tried it yet.  Good luck Smiley
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frankuitaalst
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Re: Asteroids
Reply #92 - 12/08/07 at 03:17:11
 
The recently NEA Asteroid 2007XK11 seems to be in a beautiful near resonance to Jupiter .  
Here's an animaton of the simulation covering 78 years .  
The orbit may change as more observations become available .
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2007XK11Anim.gif
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Re: Asteroids
Reply #93 - 12/21/07 at 04:41:34
 
Hey dudes !  
 
Maybe this asteroid deserve a simulation !
 
Quote:
Scientists say there is now a 1 in 75 chance the huge chunk of rock could slam into the red planet next month.

They had initially placed odds of a direct hit at 1 in 350.

"These odds are extremely unusual," said Steve Chesley, an astronomer with the Near Earth Object Programme at NASA's Jet Propulsion Laboratory.

"We frequently work with really long odds when we track threatening asteroids."

If a collision does take place, the explosion that follows could be like the famous 1908 Tunguska incident.

That blast, in central Siberia, wiped out 60 million trees and unleashed the energy equivalent to a 15-megaton nuclear bomb.

The new asteroid, known as 2007 WD5, was discovered last month and is similar in size to the Tunguska object.

 
more in :
- http://www.space.com/scienceastronomy/071220-asteroid-mars.html
 
 
The orbital elements for 2007 WD5 ( litte precise, need more observations ):
 
Epoch: 2007 11 20
Peri:  311.7
Node: 67.6
M: 2.1
e: 0.611
i: 2.3
a: 2.580
EMoid: 0.02930

 
font: http://cfa-www.harvard.edu/iau/lists/Amors.html
 
 
 
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Tony
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Re: Asteroids
Reply #94 - 12/21/07 at 10:06:41
 
Thanks for the heads-up on that asteroid.  If the current estimate holds, 2007 WD5 should miss Mars by less than 50,000 km on January 30, 2008 at 9:11 in the morning UT.  But Mars and its two moons, Phobos and Deimos are well within the error bars of this estimate and may be struck.  It will be interesting to follow the updated predictions and see if the odds of impact improve.
 
It would be very good for science if this thing did strike Mars.  With several orbiting spacecraft, we'd get some good data from below Mars' surface if it makes a crater.  With Mars' thinner atmosphere, if this is a Tunguska-sized impactor, it may make it intact to the surface.
 
Here's a simulation with its current data.  Mars, and the orbits of Phobos and Deimos are visible.  The first image is looking top-down on the ecliptic plane.  The second is from the ecliptic plane.
 


 
Here's the simulation file so you can run it yourself:
http://orbitsimulator.com/gravity/simulations/2007WD5.gsim
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frankuitaalst
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Re: Asteroids
Reply #95 - 12/21/07 at 11:33:29
 
It really would be nice if this ast would hit Mars ( Oppurtunity and Spirit watch out ! ) as Tony mentions.  
The odds of 1:75 are realistic I think .  
Herunder an animation of the orbit of the ast .
I created 4 replica's of the asteroid and put them at a 1% different position in the x and y coordinates  
( the uncertainty of the AU at this moment is about 1% AU at 1 sigma-uncetainty ).  
This means the asteroid has a path between the -sigma and sigma with 90% ( have to look up this number ) chance.  
The first frame shows Mars in the middle , to the right is the predicted path . The replicas miss Mars to the left and to the right . So theres a "good" chance the ast may hit !  
The next frames show the set of asts as they  approach Mars from the lower bottom .  
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2007WD5gif.gif
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frankuitaalst
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Re: Asteroids
Reply #96 - 12/21/07 at 13:40:20
 
The NASA came up with a nice article about 2007WD5 :  
http://neo.jpl.nasa.gov/news/news151.html
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Re: Asteroids
Reply #97 - 12/29/07 at 18:17:25
 
if this asteroid hit mars what would the crater diameter/depth be?
 
1st post Smiley
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Re: Asteroids
Reply #98 - 12/29/07 at 20:53:10
 
Quote from ssc4k on 12/29/07 at 18:17:25:
if this asteroid hit mars what would the crater diameter/depth be?

1st post Smiley

Hi.  Welcome!
The crater should be about half a mile to 1 mile, roughly 1 km.  At least that's what I've read.  No one will know for sure until (and if) it hits.
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Re: Asteroids
Reply #99 - 12/30/07 at 13:23:46
 
i searched for a program that would allow you to simulate an impact of an asteroid on a planet but i couldnt find any that allowed to you to specify the density of the asteroid and the planet, does anyone here know of any?
 
ps. this is the best thing i found.... ( http://janus.astro.umd.edu/astro/impact/ . (it let you choose the planet and set the atmmosphere but wasnt very good at the dcensity part.)
 
**Edit... Your http was missing the "h" and read as ttp .  I fixed that so the link works.  -Tony
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« Last Edit: 12/30/07 at 19:06:57 by Tony »  
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Re: Asteroids
Reply #100 - 12/30/07 at 19:05:24
 
Thanks for the link.  The biggest problem in computing the crater size is we don't know the size or composition of the asteroid.  We have good guesses, and these can set upper and lower limits on the crater size.  We've also never seen a crater get formed aside from small craters such as the recently-formed Peruvian crater.  But large objects make craters in a different way than small objects.  Small objects simply punch a hole in the ground, no different than you throwing a rock at the ground.  But large objects create an explosion that leaves you with a round crater regardless of the incoming trajectory.
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Re: Asteroids
Reply #101 - 01/02/08 at 17:54:04
 
something else ive always wanted to know. what is the closes asteroid to the sun (average of the orbit)
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Re: Asteroids
Reply #102 - 01/03/08 at 06:37:38
 
The asteroid with the closest distance to the sun is the 2007EB26. The orbit is herunder :  
http://ssd.jpl.nasa.gov/sbdb.cgi?sstr=+%282007+EB26%29&orb=1
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Re: Asteroids
Reply #103 - 01/03/08 at 12:40:17
 
hmm i thoght it would be closer than .17 au but that is pretty darn close. thanks for the link
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Re: Asteroids
Reply #104 - 01/04/08 at 15:42:49
 
If you only take gravity into account there is a stable zone inside the orbit of Mercury from 0.08 to 0.21AU where asteroids would be able to exist without being perturbed. But gravity is not the only force involved. There is an influence called the Yarkovsky effect which can change the orbits of small asteroids. Basically what happens is that the temperature of different parts of the asteroid vary because of their rotation, irregular shape or position in its orbit (season). The warmer areas radiate more heat, which exerts a small force on the asteroid. Over millions of years this force will gradually cause the asteroid to spiral inwards or outwards. Near in to the sun the effect is stronger so the Yarkovsky effect will have cleared that area of the solar system long ago. Only large objects like Mercury, which require a huge force to accelerate them, can remain there.
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