# Lab report- astrophysics

1. Mar 11, 2016

### Emily R.

1. The problem statement, all variables and given/known data
I'm writing a lab report about an experiment I did where I essentially tested the effects of various planetary characteristics on a planet's orbital period. The planetary characteristics that I tested where eccentricity, mass, and distance from the Sun (or semi-major axis). As you might imagine, I found that mass and eccentricity had virtually no effect when I changed them in the simulation I was using, but distance from the Sun did have an effect. I didn't know before I did this lab that mass and eccentricity would have no effect.

Should I write the lab report including my investigation about the eccentricity and mass, or should I write it as if I only tested distance from the Sun? I'm worried that if I include testing eccentricity and mass, it may be confusing. Specifically, if I did include them, would I have three hypotheses, one for each variable? If I don't include them, should I still mention them in my conclusion? We're supposed to write about what we learned, and I did learn that eccentricity and mass had little effect on orbital period. Should I have data tables for mass and eccentricity if they had no effect/do I need them if I make the report about testing all three?

Sorry, I hope this isn't too confusing.

2. Relevant equations
Some of Kepler's laws are relevant here, but I didn't use them.

3. The attempt at a solution
So far, I've been writing it kind of as a mix between the two. I have three hypotheses, I mentioned everything in the conclusion, but I didn't include a data table with data from testing mass and eccentricity. I also didn't mention mass and eccentricity in the method.

2. Mar 12, 2016

### Staff: Mentor

Write down what you tested. The null result for mass and eccentricity is still relevant.

Why did you do an experiment? There are exact expressions for the orbital period. The planet mass does enter those formulas, but it is added to the mass of the sun, so the effect is small.