In our solar system, smaller planets like Mercury and Venus orbit the sun closely, while larger ones like Jupiter tend to be farther away. But other solar systems don’t play by our rules.

Large planets that orbit their stars very closely — some at one-tenth the distance between Earth and the sun — are known as hot or warm Jupiters (so named because they have a mass similar to Jupiter’s). And unlike the planets in our solar system, some of these planets have unusually elliptical orbits.

Researchers at the University of California, Berkeley, set out to discover how warm Jupiters came to orbit their stars so closely, and whether the answer had something to do with their elliptical orbits.

The researchers ran more than 1,000 simulations to observe the movements of warm Jupiters relative to the other planets in their solar systems.