# Functions for properties of stars and their planets

1. May 15, 2013

### Schilcote

I'm working on a video game set in space, and I'd like my portrayal of the galaxy to be as scientifically accurate as is feasible.

I've been looking into metallicity functions, but I can't make any sense of what I'm seeing, and I don't even know where to start on the subject of algorithms for star position and planet properties.

To boil it down to a single statement, I need help finding an algorithm or series of algorithms that can procedurally generate the positions of 100,000 stars, their basic parameters, and a rough estimate of the mineral content of the planets that orbit them, giving results that are at least not blatantly impossible. I don't really care much about the simulation methods being right (as in, how these things actually came about) as much as them being simple and resembling real data. I realize this might be a tall order, and I don't expect to be spoon-fed, but I'm pretty much totally lost here. Can anyone point me in the right direction?

2. May 15, 2013

### Spourk

3. May 16, 2013

### SteamKing

Staff Emeritus
This is quite ambitious, but I doubt even Mr. Spock could help you with this.

1. Star catalogues basically compile the position of a star and its magnitude. Except for a few close stars, a lot of the data, such as distance, size, composition, etc., is either unknown or only a rough estimate.

2. Observational data on planets orbiting stars outside of the solar system dates back only about 25-30 years at the most. About all we can say about these planets right now is that we think they are in orbit about a certain star with a rough estimate of planet mass and distance from the star. (It seems like all of these planets orbit very close to their stars, where the temperature at the planet surface is hundreds, if not thousands of degrees.

A lot of basic information about stars is based on what we think we know about the stars closest to earth.
For example, Polaris is a variable star, and many of the distances to other stars is based on the observed behavior of Polaris. How far away is Polaris? It is estimated to be about 430 light years from earth, but some estimates put it 30% (or 100 light years) closer. This is quite a difference, and if it turns out Polaris is closer to earth than currently estimated, then a lot of other astronomical data will require revision.

At present, fewer than 1000 extrasolar planets have been identified.

While I admire your ambition, the scope of the information you request is simply too vast and too detailed to provide.

4. May 16, 2013

### Schilcote

Huh. But then, how do we know that the galaxy is shaped like it is? What about all those references to "simulations of galactic formation" that I ran into trying to research this problem? Surely we have enough information to mathematically determine "if there's a certain amount of gas in this area here, it's plausible that it will form into stars at these points, and they will be about this big and bright and moving at roughly this velocity" without simulating gravity on each and every particle of gas in the universe?

5. May 16, 2013

### SteamKing

Staff Emeritus
A simulation is a little bit of knowledge, a lot of speculation, a dash of hope, and a pretty picture at the end.

We think we know the structure of the Milky Way based on what we observe about the shape of other galaxies. We cannot observe the shape of the Milky Way because we are located within it and do not have access to any external vantage point.

Astronomical observations of the Milky Way from earth are confined to only a portion of this galaxy; what lies on the other side of the galactic center is too obscured to be seen from earth.

It wasn't until the 1920s that it was proved conclusively that Andromeda (M31) lies outside the Milky Way. As new observational tools are developed, more is discovered about the universe. In the aftermath, current theories are confirmed or they must undergo revision.

6. May 16, 2013

### Schilcote

Huh. Well, that's kinda disappointing.

Still, a pretty picture at the end is all I really need. Anyone know where I can find explanations of the algorithms these simulations use?

EDIT:

Come to think of it, do you think it might work to take a star chart and stick it into Eureqa?

Last edited: May 16, 2013
7. May 16, 2013

### rustytxrx

space games are never visually accurate. the conversation used is usually accurate. the graphics are designed for artistic effect (or affect) not scientific accuracy

the scale and velocities of the universe or solar system would not be very usable. If you have had calculus 3 you can set up the orbit functions and pass them to your planet CLASS.