The mystery of planet formation

A hot Jupiter races toward its star, only to be halted by a stop sign, symbolizing drag.
June 30, 2016
CreditJPL- Caltech
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Our understanding of how solar systems form is riddled with unknowns, even though it is one of the keys to finding life elsewhere in the galaxy. On July 4, NASA’s Juno probe will peer beneath Jupiter’s atmosphere, potentially revealing secrets of solar system and planet formation—including exoplanets.

One of the most common types of discovered exoplanets is known as a “hot Jupiter.” These worlds race around their stars in tight, blistering orbits. A “year” on such planets, from our perspective on Earth, can take just a few days, or even a few hours.

This raises the question: is our cold, distant Jupiter unique? Or do hot Jupiters form further out, and then move inward? One possibility is that early in the history of their solar systems, young planets encounter ripples of dusty debris, the leftover material from solar system formation. The dust causes the planets to lose momentum, the drag forcing them to migrate inward toward their stars.