I, as well as my 4 year old son, have always had an interest in Astronomy. My son puts planet puzzles together and looks at picture books. I'm proud to say that he can name all the planets in order, and astonished to realize that he knows that Pluto isn't considered a planet anymore. I've read books on Astronomy; I've been to planetariums and observatories. I've looked through various telescopes and I've watched all kinds of NASA videos. I've even been to the VLA (Very Large Array) here in New Mexico. Even so, the stars and planets still seem so... distant.

If I had to choose only one tool to learn or teach Astronomy, it would be Celestia. Celestia is a program that lets you get up close and personal with the planets and their moons, asteroids, stars and galaxies. You can even follow the International Space Station as it orbits the earth. Celestia runs on Linux, Windows and Mac and requires OpenGL.

Celestia doesn't tie you to the surface of the Earth, but instead allows you to fly around the Universe in a First Person perspective. You can travel at any speed you wish and can even change the rate at which time progresses in the simulation. All of the planets and moons have realistic orbits and are accurately rendered using very accurate textures. Many of the known asteroids and comets, such as Hale Bopp, are rendered using information from NASA. The user interface allows you to follow an object as it travels through space. By speeding up the simulation, you can follow the orbit of Saturn around the Sun, as seen from Titan, one of Saturn's moons, for example.

By right-clicking on an object, you can often bring up a web page with additional information on the object.

Learning about the planets and their moons is a lot of fun with Celestia and some of the images you can see with the program can be absolutely stunning. In figure 1, you see the view of earth from the light side of the moon. In this case, the sun would be behind us. You can also make out the haze of the Milky Way galaxy in the lower left of the image.

Figure 1.

In figure 2, you can see the rings of Saturn. You can also see the shadow that the planet casts on them. If you follow the line in the 2:00 direction, you will see Calypso, one of Saturn's moons, as well as Halley's Comet. Of course, by clicking on either object, you can fly over and get a closer look. You can actually watch Halley's Comet tumble through space.

Figure 2.

Planets/moons

In figure 3, I've picked a point in space that overlooks the solar system and I've set an option that tells Celestia to plot the orbits of the various heavenly bodies that orbit our sun. The outer orbit, depicted in blue is the orbit of Pluto. You can barely make out the orbits of the inner planets. You can also see the orbits of various comets. Suddenly, our solar system seems like a very busy place.

Figure 3.

Did you ever wonder what Halley's Comet actually looked like? I know I used to stay up at night wondering about that very thing. With Celestia, I can simply fly over and have a look, as in Figure 4. It turns out that Halley's Comet has a spectacular view of the Galaxy known as M31, which you can see in the lower right of the image.

Figure 4.

Actually, we could go and visit M31, but it doesn't seem to be all that interesting. However, I know that the we live in the Milky Way galaxy and that the Milky Way is a spiral galaxy. But what I don't really know is where in the Milky Was are we? Celestia allows you to set a marker on any object; I chose to put a marker on our sun. Then I navigated to another galaxy and turned to look at the Milky Way. Doing this allowed me to determine that we live in one of the arms of the galaxy, as seen in Figure 5. Do you see the little green X? Well, that's us. You can also see a few other galaxies in the background. By using Celestia's navigation system, you can actually fly back to earth from this far out in intergalactic space, and yes, the experience very much like something out of Star Trek.

Figure 5.

A simple trip to Google showed me how to install extra packages that define heavenly bodies that aren't included in the standard Celestia distribution. There are over 15Gb of add-ons that can be installed into Celestia, some real and some fictional. I chose to install a package that defines the Crab Nebula, otherwise known as M1. The Crab Nebula is shown in Figure 6.

Figure 6.

Earlier, I mentioned that you could use Celestia to get a look at the International Space Station (ISS) as it orbits the Earth. I've seen models of the ISS but it's really interesting to watch it as it orbits our planet. Take a look at Figure 7 to see what I mean. You can see the Earth in the background and a bit of Outer Space beyond that. I guess it was a cloudy day here on Terra Firma.

Figure 7.

As you might imagine, I could go on showing you different parts of our Universe. However, I think my editor is going to go nuts with all of the graphics I've included in this article so far. Suffice it to say that I have spent uncounted hours exploring our Universe, as well as the many features of the Celestia program.

I can only imagine what it was like in Galileo's day. In those days, Astronomers stared into telescopes with imperfect, hand-ground optics. Any calculations that had to be performed, were done without the benefit of supercomputers, or even calculators. No radar telemetry. No infra-red imaging. No radio telescopes. No Hubble telescope. Just a spot on the top of a dark hill in the middle of the night, a home-made telescope and a notepad. Amazingly, with this technology, we discovered that the Earth isn't the center of the Universe but instead revolves around the Sun and that there are several other planets revolving around our sun besides our own. We learned that Saturn and Neptune had rings around them and that there was an asteroid belt that protected the Earth from intergalactic debris.

With the help of modern technology and programs like Celestia, we and our children can skip ahead and truly appreciate many of the wonders of our Universe, and all from the comfort of our homes.

Now, I don't mean to be alarmist, but I did discover something distressful while I was wandering around the Universe. You needn't worry, though. I've informed the authorities and I've been assured that the Rebel Fleet is on it's way to neutralize the threat. But, just so you know what we're up against, I've included my discovery in Figure 8.

Figure 8.

I've found Celestia to be a lot of fun and extremely educational. My two sons enjoy being able to visit the planets in our Solar System. As a parent, it's satisfying to navigate to a planet on the computer and hear one of my sons exclaim, “Ooh, that's Saturn!”