Please add support for comets

[rockinrobbins]

Over the next month Ziacobini-Zinner will be passing by Earth very closely. I thought I'd take a look at its orbital path and animation in Universe Sandbox^2 and..........nope. No comets in the database, not Churymov-Gerisemenko, not Halley, nothin.

So I check out the add option. Surely I can add the orbital elements from the comet ephemeris. Nope, no way. As new comets are discovered and visualizing their paths is something people will automatically want to do, entering orbital elements of comets is something that will deeply disappoint (sure did for me!) users when the comet hits the headlines.

Please add a comet database and ability to enter orbital elements for new comets from their ephemeris. I'm loving US^2 and have posted several You Tube videos of surprising discoveries I've made of solar system behavior.

[Jar]

Hey rockinrobbins, glad to hear you're enjoying Universe Sandbox ²!

Both of those comets you gave as examples are in the object database. We admittedly do not have *too many* comet simulations included (though if you search in Home > Open you'll find some specific event simulations for Swift-Tuttle, Halley's, Sliding Spring, and Shoemaker-Levy). But if you search in the Add panel, you should find both of those you mentioned. My assumption is that you were searching for them in one of the solar system simulations? It's correct that these are not in there. I'll check with our team to see if there's a reason these aren't included in something like the Solar System Now & Real Time sim.

When you add these comets from the Add panel, you will need to manually enter the orbital elements. This is also something you should be able to do, so I'm curious what happened when you tried to do it. Just add any object, open its Properties panel, click on Motion, and enter the orbital elements from whatever source you have (I was able to successfully do that for Giacobini-Zinner using JPL database: https://ssd.jpl.nasa.gov/sbdb.cgi). Does that help? Or is there an issue you're running into?

Edit: After spending some more time attempting to enter these values manually, I can see that there may be an issue when it comes to calculating the current mean anomaly, as the JPL database only provides the anomaly at certain dates. So it's easy to get the right orbit, but more difficult to set it in the correct position for a specific date. I'll look into the easiest way of going about this part.

Edit again: Okay, so turns out it's not too difficult, just need to know what settings to use for JPL's HORIZONS system: https://ssd.jpl.nasa.gov/horizons.cgi. Just change "Ephemeris Type" to "Elements," set your target and dates and click "Generate Ephemeris." You'll see the MA (mean anomaly) you need listed there, along with other orbital elements. These should get you pretty accurate results in Universe Sandbox.

[Cesare]

I agree here that the asteroid "Ziacobini-Zinner" must be added to the catalog of asteroids in Universe Sandbox 2.