One-hundred ninety light-years from Earth, in the constellation Ursa Major, a planet with four times the mass of Jupiter moves in a highly eccentric orbit. For 100 days, exoplanet HD 80606b moves in an oblong route around its star. But in a span of 20 hours, the exoplanet, known as a “hot Jupiter,” shoots towards its host star, passing close enough to reach scorching temperatures.
Since astronomers have turned their sights beyond the solar system, nearly 2,000 exoplanets have been discovered. Hot Jupiters, like their namesake, are gaseous planets with orbits that take them close to their host star. The exoplanets are common, causing scientists to wonder whether the solar system is an odd duck being without one.
HD 80606b was the subject of a study recently published in The Astrophysical Journal Letters. The study used multi-day, multi-channel photometry of the exoplanet’s orbit, which was obtained by NASA’s Spitzer Space Telescope.
Over an observation period of 85 hours, the researchers discovered that the exoplanet’s star-facing side boils up to 2,000 F when passing closest to its star. But in as little as 10 hours after the approach, HD 80606b cools and disappears from Spitzer’s detection. It repeats this cycle every 111 days. Additionally, the researchers found its rotation rate was 90 hours.
“As the planet gets closer to the star, it feels a burst of starlight, or radiation,” said study co-author Gregory Laughlin, of the University of California, Santa Cruz, in a statement. “The atmosphere becomes a cauldron of chemical reactions, and the winds ramp up far beyond hurricane force.”
According to Massachusetts Institute of Technology, hot Jupiters are thought to start off with circular orbits. However, something later influences the orbit and shifts it to eccentric.
To see how long the process of change takes, the researchers look at the pliability of the exoplanet. “When HD80606b whips closely by its star, the gravity of the star squeezes it,” according to NASA. “If the planet is squishier, or more pliable, it can better dissipate this gravitational energy as heat. And the more heat that is dissipated, the faster the planet will transition to a circular orbit, a process known as circularization.”
However, HD80606b wasn’t that squishy, leading scientists to believe it will keep its highly eccentric orbit for at least 10 billion more years. It also is causing scientists to rethink theories regarding hot Jupiter migration and formation.
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