Astronomers Create a Weather Forecast for Alien Planets Beyond Our Solar System
Astronomers may have a weather forecast for a planet far beyond our solar system. Using sensitive observations from the Kepler space telescope, scientists have uncovered daily weather cycles on six extra-solar planets.
"We determined the weather on these alien worlds by measuring changes as the planets circle their host stars, and identifying the day-night cycle," said Lisa Esteves, lead author of the new study, in a news release. "We traced each of them going through a cycle of phases in which different portions of the planet are illuminated by its star, from fully lit to completely dark."
All of the planets are very near their stars, which is why they're expected to rotate counter-clockwise-just as the majority of the objects in our own solar system do. This causes an eastward movement of the planet's surface and an eastward circulation of atmospheric winds. As a result, the clouds that form on the planet's night side, where temperatures are cooler, would be blown to the planet's morning side.
"As the winds continue to transport the clouds to the day side, they heat up and dissipate, leaving the afternoon sky cloud-free," said Esteves. "These winds also push the hot air eastward from the meridian, where it is the middle of the day, resulting in higher temperatures in the afternoon."
For four of the planets, the researchers spotted excess brightness, which corresponded to when the morning side is visible. For the remaining two, the researchers saw brightness when the evening side was visible.
"By comparing the planets' previously determined temperatures to the phase cycle measurements provided by Kepler, we found that the excess brightness on the morning side is most likely generated by reflected starlight," said Esteves. "A likely explanation is that on these two planets, the winds are moving heat towards the evening side, resulting in the excess brightness."
The findings are published in The Astrophysical Journal.
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