Starry Night looks for a file called Asteroids.txt when it starts up and, if found, will load the positions of the first 100 asteroids found in this file (Enthusiast and Digital Download is limited to 10 Asteroids). Since the orbital elements of asteroids are constantly changing it is a good idea to update this Asteroids.txt file from time to time. The Asteroids.txt file is based on astorb.dat produced by Ted Bowell at the Lowell Observatory. Astorb.dat is an ASCII file of high-precision osculating orbital elements and some additional data for all the numbered asteroids and the vast majority of unnumbered asteroids (multi-apparition and single-apparition) for which it is possible to make reasonably determinate computations. Each orbit, based on astrometric observations maintained by the Minor Planet Center, occupies one 187-column record. The research and computing needed to generate astorb.dat were funded principally by NASA grant NAGW-1470, and in part by the Lowell Observatory endowment.
To download, right click (or click and hold on Macs) and, depending on which web browser you are using, pick "Save This Link As...", "Download Link to Disk", or "Save Target As...". After downloading, move Asteroids.txt to your Sky Data folder, replacing the older copy.
In Version 7 we now write/modify files in a new Sky Data folder located at:
(Windows) \Users\<YourUserName>\AppData\Local\Simulation Curriculum\Starry Night Prefs\
(Note that the AppData folder is often "hidden". A quick Googling can show you how to un-hide it)
(OS X) /Users/<YourUserName>/Library/Application Support/Simulation Curriculum/Starry Night Prefs/
If you are tracking a specific asteroid that you want to add to Starry Night try using the Orbit Editor. The Orbit Editor is a good tool for learning about celestial mechanics. Celestial mechanics is usually passed over in introductory Astronomy courses, because the mathematics and time needed to grasp orbital concepts is just too involved for most students. Starry Night provides an interactive simulator where the orbital elements of an object can be changed in a visual manner making a complex subject understandable and, dare we say it, fun.
As an example let's put an asteroid into orbit around the Sun, and observe how the orbital elements affect the orbit. The goal is to gain insight into the meaning of each of the orbital elements.
- Select File-New asteroid orbiting Sun. This will open an Orbit Editor window where we define the orbital elements of our new asteroid. By default, the name of the new object is \"Untitled\". Give the asteroid a new name.
- For Type of Object, select Asteroid.
- Click the Orbital Elements tab.
- Use the sliders to interactively change each of the orbital elements. For example, try moving the inclination slider. You'll get firsthand knowledge of the meaning of "inclination" -- a tilt in the orbit -- and the slider provides almost instantaneous feedback to any changes you make.
- Try the other sliders:
- Ascending Node: moves the node markers around (the little triangles).
- Arg of Pericenter: moves the pericenter marker around (the little line). The pericenter marks the spot where the new planet comes closest to the parent body around which it orbits.
- Mean Distance: the size of the orbit.
- Eccentricity: the higher the number, the more elliptical the orbit.
- Mean Anomaly: the position of the planet in the orbit.
- Click the Axis/Rotation/Size tab. Use the Pole Position and Diameter sliders to further customize your new asteroid.
- If you like, you can paste in a new surface maps on the Surface tab.
- Close the Orbital Editor window and Press Save.
The asteroid you have created is now a first class citizen of Starry Night, meaning that you can view from it, centre on it, etc.
Note: to remove an asteroid or planet you have created, select it on the planet palette and press Delete.