Instruction: Astronomers are finding new planets every day. There could be potentially billions of planetary systems in the universe. Compare the these discovered planetary systems with our own Solar system.

Response: One major difference between our Solar System and distant planet systems appears to be the eccentricities of those planet’s orbits. Planets in our Solar System have more or less circular orbits (with eccentricities < 10% from a perfect circular orbit), while exoplanets have up to 50% eccentricities. Exoplanets with high eccentricties may not be stable over the long-term. Another difference is that the most common size of exoplanets is super earth (that is 2-3x size of earth) while our solar system does not have any super earths.