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)?

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.