Highly Eccentric Exoplanet Raises Questions About The Origin Of ‘Hot Jupiters’

Posted: Mar 28 2016, 10:08pm CDT | by , Updated: Mar 29 2016, 7:57pm CDT, in News | Latest Science News


Highly Eccentric Exoplanet Raises Questions about the Origin of ‘Hot Jupiters’
Exoplanet HD 80606 has a highly eccentric orbit. Credit: NASA/JPL

Hot Jupiter known as HD 80606b has a wildly eccentric orbit almost like that of a comet. As the exoplanet approaches close to its star, it heats up to an extreme temperature.

Over the past few decades, astronomers have spotted a bonanza of exoplanets outside our solar system and some of those are really weird with strikingly different characteristics to Earth, indicating that our solar system is not a standard blueprint for planetary systems in universe. Most of these exotic worlds fall in the category of “hot Jupiters”, gas giants that are similar to Jupiter in its interior properties but much hotter as they orbit remarkably close to their stars.

Now, a combined team of researchers has observed a hot Jupiter known as HD 80606 b using powerful Spitzer Space Telescope. The exoplanet is located 190 light years away from Earth and the thing which makes it stand out among the hundreds of known exoplanets is its highly eccentric orbit. Instead of maintaining a circular path, HD 80606 b travels in an oblong route away from its star for 111 days much like a trajectory of a comet. Then, in just a matter of 20 hours, it comes very close to its star, nearly touching it before swinging away again. As it approaches close, the planet gets enormous energy from the star. In fact, the side facing the star heats up to a roasting temperature of roughly 2,000 degrees Fahrenheit. Then, it cools off remarkably quickly within just few hours as it orbits away.

“As the planet gets closer to the star, it feels a burst of starlight. The atmosphere becomes a cauldron of chemical reactions, and the winds ramp up far beyond hurricane force. It’s global warming gone nuts,” said co-author Greg Laughlin, a professor of astronomy and astrophysics at UC Santa Cruz. “We thought our solar system was normal, but that's not so much the case.”

Scientists theorize that something giant and massive like a nearby or planet pushes such exoplanets into a highly eccentric orbit and they gradually settle down in more tight, circular orbits over a period of hundreds of millions of years.

But the theory of planets’ migration from eccentric orbit to tighter one over millions of years does not appear suitable here because HD 80606 b is not migrating as fast as previously thought and may maintain its highly eccentric orbit for another 10 billion years or more.

If this is the case, researchers may have to rethink theories on how hot Jupiters are formed, as they may involve a mechanism different than we believe. HD 80606 b’s rotation rate is estimated to be 90 hours, which is much slower than predicted for this planet.

“This system is undoubtedly very unique as it seems to challenge in many ways our understanding of planet-star interactions and planet formation,” said coauthor Julian de Wit from MIT. “Hopefully, future studies of similar systems will help us evaluate how special this system is and how far off our initial theories were.”

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Hira Bashir covers daily affairs around the world.




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