One of the ground-breaking abilities of the James Webb Space Telescope is that researchers can use it to not only detect distant planets but also to peer into their atmosphere. Now, new research using Webb has uncovered differing conditions between morning and evening on a distant exoplanet, the first time such differences have been observed on a planet outside our solar system.
The research looked at a gas giant planet called WASP-39 b, located 700 light-years away, which Webb has previously studied to learn about its atmosphere. The planet orbits very close to its star, completing an orbit in just four days, so it is extremely hot. It is also tidally locked, meaning one side always faces the star and the other always faces out into space, so there is a big difference in conditions on each half of the planet.
The new research looks at the boundary between the side facing the star, called the dayside where it is an eternal morning, and the other side, called the nightside, which is eternal evening. The boundary, called the terminator region, was split into two semicircles representing the morning and the evening conditions.
“This is the first time that a separate measurement of a direct evening and morning spectrum of an exoplanet has been possible,” said researcher Maria Steinrück of the University of Chicago in a statement. “This method can greatly help with understanding the climate of exoplanets.”
The data showered that the evening was much hotter, at a blistering 1,450 degrees Fahrenheit (800 degrees Celsius), while the morning was cooler at 1,150 degrees Fahrenheit (600 degrees Celsius). The researchers state that the evening is likely hotter due to the presence of clouds that could keep the heat in, and also because of powerful winds of up to thousands of miles per hour that carry hot gas from the dayside to the nightside.
Taking these measurements was only possible because of Webb’s extreme sensitivity, using its NIRSpec (Near-Infrared Spectrograph) instrument to detect tiny changes in the light coming from the host star as it is filtered through the planet’s atmosphere.
“It’s really stunning that we are able to parse this small difference out, and it’s only possible due Webb’s sensitivity across near-infrared wavelengths and its extremely stable photometric sensors,” said fellow researcher Néstor Espinoza of the Space Telescope Science Institute. “Any tiny movement in the instrument or with the observatory while collecting data would have severely limited our ability to make this detection. It must be extraordinarily precise, and Webb is just that.”
