For most of human history our understanding of how planets form and evolve was based on the eight (or nine) planets in our solar system.

But over the last 25 years, the discovery of more than 4,000 exoplanets, or planets outside our solar system, changed all that.

Among the most intriguing of these distant worlds is a class of exoplanets called hot Jupiters. Similar in size to Jupiter, these gas-dominated  orbit extremely close to their parent , circling them in as few as 18 hours. We have nothing like this in our own solar system, where the closest planets to the Sun are rocky and orbiting much farther away. The questions about hot Jupiters are as big as the planets themselves: Do they form close to their stars or farther away before migrating inward? And if these giants do migrate, what would that reveal about the history of the planets in our own solar system?



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