Exoplanet Weather – From a Colleague

I always love to chat about stories by close-to-home scientists.  I just talked recently about some University of Waterloo cosmological work, but today I can follow it up with a very close to home scientist that I’ve run into a few times.  Something about seeing the achievements of those you know makes you feel pride too – it gives us all a good reason to support friends, colleagues, and even acquaintances, since we can share in their passion.

Astronomer Lisa Esteves, a PhD candidate from the University of Toronto, has been watching exoplanets carefully with the Kepler Space Telescope, seeing how they change over time, peering deeper at their atmospheres and understanding how they interact with their home stars.  Working with astronomers from York University and Queen’s University Belfast, she found evidence of daily weather cycles on six different exoplanets.

An artist’s rendering of an exoplanet with cloudy mornings and clear, scorching afternoons, exhibiting a cycle of phase variations that occur as different portions of the planet are illuminated by its star, as seen from Earth. Astronomers at the University of Toronto, York University and Queen’s University Belfast used measurements of the phase variations of six exoplanets obtained by the Kepler space telescope to forecast their daily weather cycle. Credit: Lisa Esteves/University of Toronto

The exoplanets in question exhibit phases similar to the Moon as it orbits Earth, meaning different parts of the planet are illuminated with starlight at different times.  This is causing regular weather patterns on a daily basis. The findings indicate that four of the planets have cloudy mornings, and two others have hot, clear afternoons.

“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 Esteves, lead author of the study published today in The Astrophysical Journal.  “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.”

Since the planets are close to their host stars, it is expected that they rotate counter-clockwise, in the same fashion as the planets in our own solar system (except for Venus).  This causes atmospheric winds to move Eastward, transferring clouds from the cooler night-time side of the planet to the morning daytime side, causing the cloudy morning ‘fog’ of sorts.

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 Space Telescope (KST) is the most technologically advanced telescope dedicated to the search for and study of exoplanets.  Its scientific findings since launch in March 2009 have changed the way we view the formation of planetary systems and how we view the universe in general. “The detection of light from these planets hundreds to thousands of light years away is on its own remarkable,” said study co-author Dr. Ernst de Mooij, the Michael West Fellow at 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.”

I have had the pleasure to meet Lisa Esteves several times, and she is very deserving of the accolades that come from this important and challenging work.


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