From the beginning, exoplanets have defied our expectations for what a solar system would look like.
The first planets were discovered around pulsars, then we got "hot Jupiters" which hug close to their parent stars. Lately, we've seen a planet being engulfed by its star and all kinds of weird, eccentric orbits.
New simulations presented yesterday at the American Astronomical Society meeting in Miami indicate that Earth-like exoplanets in such systems will have a tough time supporting life.
We live in a fairly ordered solar system where eight planets trace out nearly circular orbits around a mid-sized star. Massive Jupiter actually helps the Earth out by attracting much of the interplanetary debris that could otherwise threaten our comfortable planet.
However, if Jupiter were to have a much more elliptical orbit, it could knock Earth out of the habitable zone, or the sweet spot around a star where liquid water can exist on a planet's surface. Astronomers with NASA's Virtual Planetary Laboratory ran simulations of such scenarios, drawing from the rich diversity of exoplanet systems that have been discovered so far.
With a highly elliptical gas giant in the neighborhood, the smaller planet in these simulations would cycle between habitable and uninhabitable conditions, sometimes with a period of just 1000 years. It could support life as we know it sometimes, but other times be frozen over, or boil off all of its water.
This has serious implications for the search for Earth-like planets, which is expected to ramp up as Kepler continues its three year mission. Just because a planet is in a good spot now, it might not always be, depending on its environment. As biological evolution on Earth has shown, a lot of time is needed to build up complex organisms.
If this is too depressing for those of you hoping to find life elsewhere, I have the solution. Push around your own little Earths! PhET Interactive Simulations at the University of Colorado has a really fun gravitational simulator called My Solar System. With just a little bit of fiddling, I was able to get a large planet in an elliptical orbit and a smaller, closer planet with a range of orbits. Warning: you will get really distracted making your own wacky solar system, so don't plan on doing any work for a while!
Image credit: "Extreme Planets," Clark Planetarium Productions