When you think about all the exoplanets that have been discovered in the last five years it’s easy to chalk up the discoveries to the work of the revitalized Kepler Space Telescope and its quest to find life outside of our solar system. However, the Spitzer Space Telescope’s own work shouldn’t be overlooked.
5,000 unclassified exoplanets and “hot Jupiters”
In addition to the nearly 2,000 exoplanets that have been discovered in recent years, there are also about 5,000 exoplanet candidates a number of which are so called “hot Jupiters.” These gas giants get their name from the fact that like Jupiter they are gas giants but are considerably hotter than Jupiter owing to orbits that take them frighteningly close to the star the orbit.
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This freakish orbit seemed strange to most studying them but now that so many objects which get that close to their stars, a couple of scientists are reconsidering this view of the misfit gas giants and wondering if that sort of orbit isn’t more the norm in the universe than originally thought.
“We thought our solar system was normal, but that’s not so much the case,” said astronomer Greg Laughlin of the University of California, Santa Cruz, co-author of a study accepted for publication in Astrophysical Journal Letters.
Along with lead author Julien de Wit of the Massachusetts Institute of Technology, the two used the Spitzer Space Telescope to observe a hot Jupiter known as HD 80606b, 190 light-years from Earth. The two especially studied the strange orbit that this giant makes every 111 days. It’s reminiscent of a comet’s orbit owing to an acutely elliptical orbit that brings it close to its star heating one side of the planet to temperatures exceeding 2,000 Fahrenheit.
Spitzer upgrade and more time
“As the planet gets closer to the star, it feels a burst of starlight, or radiation. The atmosphere becomes a cauldron of chemical reactions, and the winds ramp up far beyond hurricane force,” said Laughlin.
What the two noticed is that they believe that over time, these gas giants leave their eccentric orbits and owing to the gravity of other stars and planets get pulled into a tighter orbit over the course of hundreds of millions of years.
“This planet is thought to be caught in the act of migrating inward,” said de Wit. “By studying it, we are able to test theories of hot Jupiter formation, he continued.
“The Spitzer data are pristine,” said de Wit. “And we were able to observe the planet for much longer this time, giving us more insight into its coldest temperature and how fast it heats up, cools down and rotates.”
The two had trained Spitzer on another hot Jupiter before but because of Spitzer’s improved sensitivity and the 85 hours allowed to observe HD 80606b, they believe they have a better understanding of hot Jupiters. The tow observed a “squishyness” that determines how long it takes for the planet’s orbital migration will take. When hot Jupiters near a star gravity effectively squeezes out heat and the more heat it loses the closer it will get to a circular orbit.
“If you take a Nerf ball and squeeze it a bunch of times really fast, you’ll see that it heats up,” said Laughlin. “That’s because the Nerf ball is good at transferring that mechanical energy into heat. It’s squishy as a result.”
“We are starting to learn how long it may take for hot Jupiter migration to occur,” said de Wit. “Our theories said it shouldn’t take that long because we don’t see migrating hot Jupiters very often.”
“The long time scales we are observing here suggest that a leading migration mechanism may not be as efficient for hot Jupiter formation as once believed,” said Laughlin.
It’s all quite interesting but the two didn’t get their beloved hot Jupiters any closer to exoplanet designation.