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Charting Apophis
I've got an old (2000) version of Starry Night.
Just for fun, I was entering the data for the asteroid Apophis in it, the one that on April 13th, 2029, will come closer than geosynchronous satellites. My thought being, I could speed it up and do an Earth-flyby like a rollercoaster ride. I got them from JPL's website: Orbit: Near-Circular Reference Plane: Ecliptic 2000 Mean Distance (a) (in AU) 0.922261415 Eccentricity (e) 0.191059415 Inclination (i) 3.331314642 Ascending Node 204.4591523 Arg of Pericenter 126.3855713 Mean Anomaly (L) 307.3630785 Epoch (Julian Date) 2454200.5 Then I fast-forwarded to around April 13th, 2029. In my simulation, it came to its closest approach to Earth on April 14th, 2029, around 13:00 UT, so one day late. And the nearest it got to Earth seemed to be around 2.6 million miles, rather than the 22,000 miles or so it should have been at, so off by roughly a factor of 100. Still, fairly impressive for calculating 22 years in the future. I realize that I've probably reached the limits of this program to do this kind of thing, and it's not taking gravity effects into account. Are there other programs out there that could fairly accurately show this fly-by? (or, for example, will a newer version of Starry Night handle it better)? |
#2
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Charting Apophis
On Sat, 11 Aug 2007 07:57:04 -0400, "algomeysa2"
wrote: Are there other programs out there that could fairly accurately show this fly-by? (or, for example, will a newer version of Starry Night handle it better)? The accuracy of your orbital elements is the limiting factor. Elements for asteroids change significantly over time due to perturbations, making orbits calculated using them inaccurate when computed much into the future or past. I imagine JPL's ephemeris showing the close approach was computed by numeric integration. I don't think anyone has worked out a theory for Apophis. The situation is that theories exist for the eight planets, but not for Pluto or any of the minor planets. Their keplerian elements are developed from orbits computed by numeric integration and are good only for a limited period of time. Someone will correct me if I'm wrong on that point. Bud -- The night is just the shadow of the Earth. |
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