Celestia Forums

Hello all,

I just installed Celestia the other day, and I think it is a great program.
I am not a astronom, so I am not familiar with a lot of technical terms, but with this program the accesibility of astronomy is a lot better.

I wonder if someone can help me with the following questions:

Is it possible to view the impact of the 2 (i think it was 2 ) asteroids that came in collision with Jupiter?

What date did this occur?
Do i need to load some extra data?

I am currently using version 1.2.4

Gerrit,

I suspect you may be thinking of the collision of the 21 (!) pieces of Comet P/Shoemaker-Levy 9 with Jupiter, which happened in July, 1994.

Some orbital definitions for use with Celestia can be found at http://www.lns.cornell.edu/~seb/celestia/comets.html#3.3.3

I hope this helps.

You where correct in your assumption.
I was looking for the Shoemaker Levi asteroids.
I didn't know that there were 21! fragments.

Thanks for the link

I only noticed 1 odd thing in Celestia.
After the collision the asteroids continue on there (theoretical path), which of coarse is not atually the case.
One might find a new collission somewhere in the future which cannot occur.

But ok, nothing is perfect so we have to live with that.

Thanks again.

Gerrit,

Actually, now the fragments can be made to terminate in Jupiter.

Starting with version 1.2.5 of Celestia, Beginning and Ending commands are available to limit when objects are visible. I just haven't updated the SL9 SSC files to use them.

RSN.

Well I for one wouldnt mind seeing this in action...

Ras',

I'm not sure what you mean by "in action", since Endings remove action

If you mean the black spots on Jupiter where the comet pieces exploded, that's a bit more than I'm willing to spend time on right now. It'd take more than 22 Jupiter surface textures (so the spots fade appropriately) with appropriate blotches added as each subsequent piece hits, each with its own Beginning and Ending.

Anyhow, I've updated SL9_JOVIAN.SSC (the one that has elliptical orbit definitions relartive to Jupiter) with appropriate Ending directives so that the cometary pieces don't come out the other side of the planet.

After installing it, set Celestia to 16 July 1994, somewhat before 20:00 UDT and follow them in.

It's available in http://www.lns.cornell.edu/~seb/celestia/sl9.zip.

Selden,

I now have installed V1.2.5, and with your latest ssc file it looks very good.

It would be nice to see the explosions, but that is not the purpose of this program, I presume.
It looks very nice with the current modifications.

The eclipse finder is a nice new option in 1.2.5

Thanks again!

Gerrit,

The purpose of Celestia is what you make of it

Animated textures have been on people's wish lists for a long time, but it'd be a lot of coding. In the meantime, one can do the equivalent of "page flipping." Beginning and Ending directives can be used to define objects that replace one another at appropriate times.

It just takes someone with the patience to make enough versions of the picture that's used as Jupiter's surface texture. Each would have to have blotches and bright spots in the right places and at the right times. I suspect there are enough pictures on the Web to figure out most of the blotch positions. (they would not necessarily match up with where "my" sl9 fragments seem to impact) I don't know if the differential rotation of Jupiter's clouds is enough to matter for this.

Selden, Hi. I downloaded the Shuemaker-Levy files and tried to watch the collisions, but because the comets were relatively close, the comet tails were so large that the entire scene got totally overwelmed by them. I tried changing vantage points. If I was on a comet, it was enveloped in its tail. If I was on Jupiter, the incoming tail eventually enveloped it too. To make the tails realistically small enough in relation to Jupiter, I had to zoom way out so that Jupiter was a small sphere. Eventually, I just turned comet tails off and enjoyed the show. Is there any way to reduce the size of a comet tail? Am I doing something wrong here?



Frank G

Frank,

The size of the comet tail drawn by Celestia is proportional to the size of the body. One way to show it the way you want, I think, would be to define tiny comets that follow exactly the same paths as asteroids that are the (larger) right sizes. In other words, each "comet" would be defined as two separate bodies.

Does this help?

Dear Selden. I'll give it a try. Thanks for the tip. It should work. I presume I should superimpose the tiny comet on the asteroid by using the identical orbital parameters. If that is not what I should do, let me know.

Frank

Frank,

You're exactly right.

All of the parameters should be the same except for
1) the object name
2) the object type
3) the object size.

hi all
dunno if this will help or not, but what i did was used sun-centred xyz coordinates for the fragments, and then did selden's idea

The size of the comet tail drawn by Celestia is proportional to the size of the body. One way to show it the way you want, I think, would be to define tiny comets that follow exactly the same paths as asteroids that are the (larger) right sizes. In other words, each "comet" would be defined as two separate bodies.

which worked great! i heard somewhere that SL9 had actually been locked in orbit around jupiter since around 1920 or so!! i have my xyz files starting in 1980 up until the impacts, but theyre around 550KB each though so a bit too big...

On a completely unrelated topic- if i converted all my textures to DXT would it speed up celestia a lot or would it be worth the hassle?

Thanx!

Jack, could you include your xyz coordinates somewhere so we could cut and paste them?

Frank

I only have fragments A,B,C,& D fully done the others only go until 1990 (work in progress )
Those arent perfect either though they get a bit jerky in places- check this topic again at around 9.30 PM GMT & i'll post an update then; i should have them all finished by the end of the week for sure!!

The suspense...

ok update- i wont have them finished today sorry, but i'll defnitly have ABC&D finished by tomorrow night il post the adress then & whats happening with the others. They'll be finished soon hopefully!