A telescope observing distant planets has found evidence of weather patterns, allowing astrophysicists to "forecast" their conditions.
Analyzing data from NASA's Kepler space telescope, a team of astrophysicists at universities in Canada and Great Britain has identified signs of daily weather variations on six exoplanets.
They observed phase variations as different parts of the planets reflected light from their host stars, in much the same way that our moon cycles though different phases.
"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 from the Department of Astronomy and Astrophysics at the University of Toronto.
"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," added Esteves, who the led the team on the study.
The scientists have offered up "forecasts" of cloudy mornings for four of the planets, and clear but scorching hot afternoons on two others.
They based their predictions on the planets' rotations, which produce an eastward motion of their atmospheric winds. That would blow clouds that formed over the cooler side of one of the planets around to its morning side — thus producing the "cloudy" morning forecast.
"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."
The Kepler telescope has proven to be the ideal instrument for studying phase variations on distant exoplanets, according to the researchers.
The massive amounts of data and the extremely precise measurements that the telescope is capable of permits them to detect even tiny, subtle signals coming from the distant world, and to separate them from the almost overwhelming light coming from their host stars.
"The detection of light from these planets hundreds to thousands of light years away is on its own remarkable," said co-author Ernst de Mooij from the Astrophysics Research Centre from the School of Mathematics and Physics at Queen's University, Belfast.
"But when we consider that phase cycle variations can be up to 100,000 times fainter than the host star, these detections become truly astonishing."
There may come a day when a weather report for a distant planet is a common and unremarkable event, the researchers added.
"Someday soon we hope to be talking about weather reports for alien worlds not much bigger than Earth, and to be making comparisons with our home planet," said Ray Jayawardhana of York University in England.
This study was published in The Astrophysical Journal.
