I recently spoke with Chris Laurel of the Celestia project. Celestia is a 3-D planetarium.
Rich: This is Rich Bowen and I’m speaking with Chris Laurel who is a member of the Celestia project. Thanks so much for taking the time to speak with me. Tell me something about Celestia. Tell us what it does and tell us how you got involved in this project.
Chris: Celestia is about 10 years old as of … well, actually it’s about 11 years old now, and I started it after leaving a job and taking some time off. I wanted to keep doing something related to my field, which is 3-D graphics programming. And I wanted to do something with 3D graphics that was something beyond just a game. I wanted to demonstrate that there’s some usefulness to the 3-D graphics beyond special effects for movies and games. And so, I decided to create Celestia. The other reason is that I’ve had a lifelong interest in astronomy and I always wondered what would be like actually stand on the surface of what the moons of Jupiter. This was right around the time that were starting to get some of these extrasolar planet discoveries and wondered what would the sky look like from the surface of these planets we were finding around other stars.
And so the desire to make something useful with 3D graphics plus my interest in … wondering what it would look like to be in these places was what made me develop Celestia.
Celestia is a 3-D planetarium that lets you look at the universe from any point in space and at any particular time. So you can see the motions of planets around our sun. You can zoom away from our sun and see thousands of stars near by in 3 dimensions. You can zoom out further and see our galaxy and where it is located relative to other nearby galaxies. You can observe the motions of planets in time and the motions of binary stars orbiting each other. It’s really meant to give you this broad view of the universe – this visual experience
Rich: Where does your data come from?
Chris: We have a lot of sources. There’s no single catalog that covers all these different objects. Stars are from the European space agency Hipparcos mission. This is to date the only large catalog of stars that has their distances measured. It turns out that accurately measuring the position of star in the sky is very easy but measuring the distance requires extremely high precision. So far the only catalog available is the Hipparcos catalog.
The orbits of the planets come from different sources. There’s something called the VSOP 87 which is this complex theory for the orbits of the planets in our solar system. Then there are other theories for the orbits of the moons around planets.
The surfaces of the planets and moons are derived from images acquired by missions to various planets. Voyager, Cassini, the Viking Mission to Mars. Pretty much all the interplanetary missions in the last couple decades have contributed in some way to Celestia.
Rich: Is all of that data free?
Chris: Yes, it’s all free. This is all scientific data, and it’s all generated by these government supported agencies like NASA and the European space agency and JAXA from Japan. And they all make this data freely available so that scientists can analyze it and then write papers and learn things about our universe.
Rich: What kind of things do you have in the pipeline for future versions of Celestia.
Chris: I think one of the most important things right now is sorting out the user interface a little bit. A common complaint about the Celestia is that it’s extremely hard to figure out all the different non-obvious keyboard commands that are required to navigate around the universe. That’s an area where Celestia needs some development. And then we always want to improve the visual qualities of Celestia – just improve the graphics, make it look more realistic, take advantage of some of the new features are available in 3-D graphics hardware that were not available when we started 10 years ago.
Rich: I noticed while looking through the release history that there’s a two year gap, about 2009 until early this year. What inspired you to pick the project back up and start releasing versions again?
Chris: It’s free software so I don’t make money from Celestia. There’s times when I have to work on other projects and I get busy with those. When I have more free time available, I do more work on the project. There are other people that are also working on Celestia. I’m certainly not the only developer. They have similar time constraints. We’re all doing this for fun. We don’t get paid. When we have time available, we work on it. But unfortunately as you’ve noticed, we don’t have enough time to be constantly updating it. So there’s gaps.
Rich: Yeah, one never does.
Rich: If someone wanted to get involved in your project, what sort of openings might there be?
Chris: Celestia supports these add-ons which are our packages of data about planets galaxies and stars, that you can use to expand the universe in Celestia. And so we’re always looking for people to take new data sets from planetary missions or from telescopic missions, and importing that into Celestia to expand the universe of Celestia. Make sure we have all the latest, and most accurate, and most complete data available.
Rich: Tell me some more about these plug-ins. How many contributors do you have for that? What sort of data they brought to the project?
Chris: Maybe 100 people or so have contributed add-ons and made them publicly available. I know they’re quite a few more people that create these things just for their organizations or for their own entertainment. There’s a site called the Celestia Motherlode where a lot of people have uploaded these add-ons. Things you can find there are high-resolution planet textures, 3-D models of asteroids and spacecraft, and the trajectories of the spacecraft. So you can follow the New Horizon’s mission to Pluto or the MSL – the Curiosity mission to Mars. Catalogs of comets. Then there are things that are more speculative, such as … people will take the known data about an extra-planetary system, and expand on it and produce their own imagined surfaces for these planets around other stars. And then there’s a lot of people that like to use it to take spacecraft from Star Trek or something like that …
Rich: [laughs] I was going to ask that.
Chris: Yeah. There are a lot of people doing that, and that’s certainly not something that we have in the base Celestia package which is all completely reality-based. If people want to use it to live their favorite science fiction series or movie that’s great.
Rich: That’s pretty cool. I was just going to ask if anyone was using it for fictional stuff.
Chris: Yeah, in fact some of the Star Trek models in particular have gotten very detailed, and really well done. It’s cool stuff, even though it’s not not my domain.
Rich: My wife and I are big Trek fans. Maybe I’ll play with that some.
Chris: You absolutely should. The Trek stuff is great. We have some very devoted Trek fans who are Celistia users.
One thing I’d like to say is that we’re pretty careful about what data we allow in Celestia. We try to keep it very realistic and don’t enhance anything. But we have to make some guesses in a few places, such as these extrasolar planets. We have some speculation as to what they look like, but we can’t see them from Earth right now. We don’t have telescopes that are powerful enough. So we sort of have to make some guesses there. But in general, there’s very little speculation involved in the visuals in Celestia.
I always like to emphasize this is … just because I’m talking about Celestia doesn’t mean I’m the the sole developer by any means. We’ve had a lot of people contributing over the last decade on the project, and not just in creating add-ons, but a lot of work on the code a lot of work on the very complex process of taking these scientific data sets and turning them into something you can visualize in your PC. I always like to make sure that credit is given here.
Rich: Thanks so much for talking to me.
Chris: Thank you, and have fun exploring Celestia!