The next program contains data and a simulation of binary star orbits. Now instead of moons orbiting a much larger planet, you will see two nearly-equal mass stars orbiting their mutual center. Here again, you select a star system from the menu, and the data are displayed in the window to the right side. All are real star systems, observed by the Hipparcos satellite. You will see two "privileged" points of view: one where the system is face-on to you, so you see the full orbit, and one where the system is edge-on to you, so the stars appear to travel back and forth in a line. In the first view, you'll see not only the data for your star, but also a spectrum which identifies the type of star. In the second view you see the same spectrum, but also a "high-resolution" spectrum which displays a real-time doppler effect as the orbit progresses.

Finally, after you have become experts on orbits, you'll explore two protoplanetary disks, where there is a full distribution of matter, not just points in orbits. In these programs, you can click on the image, and positions and doppler velocities are displayed in the box.

With the experience gained in from working with planets around stars, we then: then/endif not found. then turn to images (negative photographs) and doppler velocities from spiral galaxies. If you click with the mouse on a position in the galaxy image, the projected coordinates (in kiloparsec) will be displayed in the box to the right. Please note, however, that these coordinates are not truly meaningful for positions that do not include some part of the galaxy. If you select one of the magenta squares, then a doppler velocity is also displayed.