The Solar System

What is a hot Jupiter?
Answered by Dr. Evgenya Shkolnik
  • Dr. Evgenya Shkolnik

    Dr. Evgenya Shkolnik

  1. Dr. Evgenya Shkolnik Astronomer, Lowell Observatory


    A hot Jupiter is an extrasolar planet that orbits its star very close in. So to contrast with our Jupiter, our Jupiter orbits at five astronomical units from the sun. It's fairly cold and has a very long period of about 12 years. A hot Jupiter is this class of extrasolar planets that are being discovered where the planet is really right up against the star, only a few stellar radii away, and has an orbital period of three days, some even one and a half days. These are roasters. Their temperatures are between 1,000 and 2,000 kelvin, so they're quite remarkable.

    They were the first extrasolar planets to be confirmed, in part because they were the easiest to find. They have the largest gravitational tug on their stars, so their signature in the Doppler method of planet hunting is the strongest. Initially, they were a complete surprise. Planet formation models never predicted hot Jupiters, and right now it seems to be that hot Jupiters make up 20 percent of all known extrasolar planets.

    More answers from Dr. Evgenya Shkolnik »

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