Celestia Forums

Astronomers have just discovered this asteroid that shares earth's orbit.
here's a quote from the BBC news story on it:

Analysis of 2002 AA29's motions have revealed a remarkable event that happens to it every few thousand years.

In 550AD, and again in 2600AD and 3880AD, for a while it will become a true satellite of our planet, in effect Earth's second moon, although technically it will remain under the gravitational control of the Sun.

It remains a second moon to Earth for about 50 years until it escapes.

(http://news.bbc.co.uk/1/hi/sci/tech/2347663.stm)

I remember a thread or two a while back about adding horseshoe orbits to celestia... how are these coming along?

It'd be quite cool to go back to 550AD in celestia and see earth get a second moon!

A quibble with the BBC article: they claim that there are 8 known Martian trojans. The Harvard/Smithsonian Minor Planets Center's web site at http://cfa-www.harvard.edu/iau/lists/MarsTrojans.html only lists 6 confirmed as of September 19th. (I suspect someone misread a scribbled 6 as an 8.) Of course, the CfA list could be incomplete, so I'd appreciate a link to any reference that shows there to be more than 6.

Speaking of objects in unusual orbits, did you all see this one (J002E3)?

http://neo.jpl.nasa.gov/news/news134.html

Be sure to view the animation.

- Hank

HankR wrote:Speaking of objects in unusual orbits, did you all see this one (J002E3)?

http://neo.jpl.nasa.gov/news/news134.html

Be sure to view the animation.

- Hank

I created a .xyz file for J002E3 that you can use in Celestia:

http://www.shatters.net/~claurel/trajectories/j002e3.xyz

I'll post my .ssc file soon, though I don't have a model of the Apollo booster.

--Chris

chris wrote:

HankR wrote:Speaking of objects in unusual orbits, did you all see this one (J002E3)?

http://neo.jpl.nasa.gov/news/news134.html

Be sure to view the animation.

- Hank

I created a .xyz file for J002E3 that you can use in Celestia:

http://www.shatters.net/~claurel/trajectories/j002e3.xyz

I'll post my .ssc file soon, though I don't have a model of the Apollo booster.

--Chris

what are these .xyz files, what do they do, and how do you use them?

billybob884 wrote:what are these .xyz files, what do they do, and how do you use them?

.xyz files contain a set of points describing the trajectory of an object for some finite time span. They're useful for spacecraft and other cases where an ellipse just isn't a reasonable approximation. .xyz files go in the data directory. To use one, you need to add a line like:

SampledOrbit "foo.xyz"

in an .ssc file. Here's the .ssc for J002E3:

http://www.shatters.net/~claurel/trajectories/j002e3.ssc

Put it in the extras directory, and this file:

http://www.shatters.net/~claurel/trajectories/j002e3.xyz

in the data directory, and you'll be able to watch J002E3 get captured, orbit the Earth a few times, and drift back to a solar orbit over a period from March 2001 to June 2002. (Unfortunately, it looks a lot more like a featureless sphere than a rocket booster right now )

--Chris

Im interested in how to code xyz files...but looking at it its all numbers so what are the basics?

You have the first two lines of the file like:
2452334.553472 -135719191.6623067260 50774714.1626013592 46434.462271

2452334.803472 -135964230.3632186055 50171015.8145814985 45980.891214

Is this xyz and distance at these points [RA and Dec?]? and its thier a time variable before it reaches the next point or am I WAY off

I think the first item in each enty is the Julian date at which the object is at the specified coordinates.

- Hank