Nav: Home

A 'hot Jupiter' with unusual winds

January 22, 2018

The hottest point on a gaseous planet near a distant star isn't where astrophysicists expected it to be - a discovery that challenges scientists' understanding of the many planets of this type found in solar systems outside our own.

Unlike our familiar planet Jupiter, so-called hot Jupiters circle astonishingly close to their host star -- so close that it typically takes fewer than three days to complete an orbit. And one hemisphere of these planets always faces its host star, while the other faces permanently out into the dark.

Not surprisingly, the "day" side of the planets gets vastly hotter than the night side, and the hottest point of all tends to be the spot closest to the star. Astrophysicists theorize and observe that these planets also experience strong winds blowing eastward near their equators, which can sometimes displace the hot spot toward the east.

In the mysterious case of exoplanet CoRoT-2b, however, the hot spot turns out to lie in the opposite direction: west of center. A research team led by astronomers at McGill University's McGill Space Institute (MSI) and the Institute for research on exoplanets (iREx) in Montreal made the discovery using NASA's Spitzer Space Telescope. Their findings are reported Jan. 22 in the journal Nature Astronomy.

Wrong-way wind

"We've previously studied nine other hot Jupiter, giant planets orbiting super close to their star. In every case, they have had winds blowing to the east, as theory would predict," says McGill astronomer Nicolas Cowan, a co-author on the study and researcher at MSI and iREx. "But now, nature has thrown us a curveball. On this planet, the wind blows the wrong way. Since it's often the exceptions that prove the rule, we are hoping that studying this planet will help us understand what makes hot Jupiters tick."

CoRoT-2b, discovered a decade ago by a French-led space observatory mission, is 930 light years from Earth. While many other hot Jupiters have been detected in recent years, CoRoT-2b has continued to intrigue astronomers because of two factors: its inflated size and the puzzling spectrum of light emissions from its surface.

"Both of these factors suggest there is something unusual happening in the atmosphere of this hot Jupiter," says Lisa Dang, a McGill PhD student and lead author of the new study. By using Spitzer's Infrared Array Camera to observe the planet while it completed an orbit around its host star, the researchers were able to map the planet's surface brightness for the first time, revealing the westward hot spot.

New questions

The researchers offer three possible explanations for the unexpected discovery - each of which raises new questions:
  • The planet could be spinning so slowly that one rotation takes longer than a full orbit of its star; this could create winds blowing toward the west rather than the east - but it would also undercut theories about planet-star gravitational interaction in such tight orbits.

  • The planet's atmosphere could be interacting with the planet's magnetic field to modify its wind pattern; this could provide a rare opportunity to study an exoplanet's magnetic field.

  • Large clouds covering the eastern side of the planet could make it appear darker than it would otherwise - but this would undercut current models of atmospheric circulation on such planets.


"We'll need better data to shed light on the questions raised by our finding," Dang says. "Fortunately, the James Webb Space Telescope, scheduled to launch next year, should be capable of tackling this problem. Armed with a mirror that has 100 times the collecting power of Spitzer's, it should provide us with exquisite data like never before."
-end-
Scientists from the University of Michigan, the California Institute of Technology, Arizona State University, New York University Abu Dhabi, the University of California, Santa Cruz, and Pennsylvania State University also contributed to the study.

"Detection of a westward hotspot offset in the atmosphere of hot gas giant CoRoT-2b," Lisa Dang, Nicolas B. Cowan, Joel C. Schwartz, et al. Nature Astronomy, Jan. 22, 2018. https://doi.org/10.1038/s41550-017-0351-6

Funding for the research was provided in part by the Natural Sciences and Engineering Research Council of Canada and the California Institute of Technology's Infrared Processing and Analysis Center.

McGill University

Related Planets Articles:

Ultracool dwarf and the 7 planets
Astronomers have found a system of seven Earth-sized planets just 40 light-years away.
ALMA measures size of seeds of planets
Researchers using the Atacama Large Millimeter/submillimeter Array (ALMA), have for the first time, achieved a precise size measurement of small dust particles around a young star through radio-wave polarization.
Origin of minor planets' rings revealed
A team of researchers has clarified the origin of the rings recently discovered around two minor planets known as centaurs, and their results suggest the existence of rings around other centaurs.
Are planets setting the sun's pace?
The sun's activity is determined by the sun's magnetic field.
A better way to learn if alien planets have the right stuff
A new method for analyzing the chemical composition of stars may help scientists winnow the search for Earth 2.0.
A new Goldilocks for habitable planets
The search for habitable, alien worlds needs to make room for a second 'Goldilocks,' according to a Yale University researcher.
Probing giant planets' dark hydrogen
Hydrogen is the most-abundant element in the universe, but there is still so much we have to learn about it.
Universe's first life might have been born on carbon planets
Our Earth consists of silicate rocks and an iron core with a thin veneer of water and life.
Number of habitable planets could be limited by stifling atmospheres
New research has revealed that fewer than predicted planets may be capable of harbouring life because their atmospheres keep them too hot.
Footprints of baby planets in a gas disk
A new analysis of the ALMA data for a young star HL Tauri provides yet more firm evidence of baby planets around the star.

Related Planets Reading:

Best Science Podcasts 2019

We have hand picked the best science podcasts for 2019. Sit back and enjoy new science podcasts updated daily from your favorite science news services and scientists.
Now Playing: TED Radio Hour

Bias And Perception
How does bias distort our thinking, our listening, our beliefs... and even our search results? How can we fight it? This hour, TED speakers explore ideas about the unconscious biases that shape us. Guests include writer and broadcaster Yassmin Abdel-Magied, climatologist J. Marshall Shepherd, journalist Andreas Ekström, and experimental psychologist Tony Salvador.
Now Playing: Science for the People

#514 Arctic Energy (Rebroadcast)
This week we're looking at how alternative energy works in the arctic. We speak to Louie Azzolini and Linda Todd from the Arctic Energy Alliance, a non-profit helping communities reduce their energy usage and transition to more affordable and sustainable forms of energy. And the lessons they're learning along the way can help those of us further south.