Hubble Telescope Enables Observations of Exoplanetary Weather by Scientists

Using data from NASA’s Hubble Space Telescope, a team of international astronomers has made a groundbreaking discovery regarding atmospheric variability on an exoplanet called WASP-121 b. This Jupiter-sized exoplanet, located approximately 880 light-years from Earth, has a unique set of characteristics that make it an ideal candidate for studying weather patterns on exoplanets.

One of the most significant factors contributing to the excitement surrounding this discovery is the planet’s close proximity to its host star. Completing one orbit around the star in just 30 hours, WASP-121 b experiences intense gravitational forces that almost tear it apart. Additionally, the exoplanet is tidally locked, meaning that one hemisphere always faces the star and is exposed to its ultraviolet light, resulting in extreme temperatures.

Quentin Changeat, one of the principal investigators from the Space Telescope Science Institute in Baltimore, Maryland, expressed his enthusiasm, stating, “This is a hugely exciting result as we move forward for observing weather patterns on exoplanets.” Understanding exoplanet atmospheres and their complexities is important in the search for habitable conditions on other worlds.

To study this extreme exoplanet, scientists had to gather a comprehensive data set comprising multiple observations taken over a three-year period. These observations were then analyzed and combined with computer simulations to reconstruct the atmospheric conditions responsible for the observed variability.

Changeat further explains the significance of their data set, stating, “The assembled data set represents a significant amount of observing time for a single planet and is currently the only consistent set of such repeated observations. The information extracted from those observations provided us with an exquisite picture of the planet changing over time.”

But why was a special data set necessary to observe weather patterns on WASP-121 b? Most exoplanets cannot be directly observed; instead, astronomers must carefully measure their effect on the light emitted by their host stars. During a transit, when an exoplanet passes between its star and Earth, the star appears slightly dimmer than normal. By measuring these transits, valuable information about the exoplanet can be obtained.

However, observing an exoplanet’s atmosphere presents even greater challenges. When a star’s light dims during a transit, an even smaller fraction of light passes through the planet’s atmosphere, slightly altering the detected spectrum of light. By analyzing these changes, astronomers can determine the composition of the exoplanet’s atmosphere.

To amplify these minute signals and reduce noise, astronomers often combine multiple observations into an average. However, this makes it impossible to measure changes over time. Given the limited availability of telescopes, single observations are rarely repeated.

Fortunately, Hubble’s Wide Field Camera 3 has observed WASP-121 b four times, totaling approximately 90 hours of observation time. The data collected in 2016, 2018, and 2019 allowed the team to analyze the exoplanet’s atmosphere at different points in time, without encountering incompatibilities between observations from different telescopes.

The astronomers discovered that the exoplanet’s hot spot had shifted between the different observations, indicating variations in the chemical composition of its atmosphere. By utilizing computer simulations, they identified weather patterns that could explain the observed changes. These simulations demonstrated that temperature differences between the star-facing and dark side of the planet could give rise to massive storms and cyclones.

Co-author Jack Skinner of the California Institute of Technology emphasized the significance of their findings, stating, “The remarkable details of our exoplanet atmosphere simulations allow us to accurately model the weather on ultra-hot planets like WASP-121 b. Here we make a significant step forward by combining observational constraints with atmosphere simulations to understand the time-varying weather on these planets.”

The recent study on WASP-121 b is just one of many conducted in recent years. The planet and its host star have been observed by various telescopes, including the Spitzer Space Telescope, the James Webb Space Telescope, and ground-based telescopes. Previous studies have revealed that the planet’s atmosphere becomes so hot that metals like iron and magnesium escape its atmosphere instead of forming clouds.

The study conducted by Changeat and his team has been accepted for publication in The Astrophysical Journal Supplement journal, solidifying the significance and credibility of their findings. The ability to observe weather patterns on an exoplanet represents a significant leap forward in our understanding of these distant worlds and their potential habitability.

In conclusion, the researchers’ use of NASA’s Hubble Space Telescope to observe atmospheric variability on WASP-121 b provides crucial insights into weather patterns on exoplanets. By combining multiple observations and utilizing advanced computer simulations, the scientists were able to reconstruct atmospheric conditions and demonstrate the existence of weather patterns. This groundbreaking research paves the way for future studies on exoplanet atmospheres, enhancing our understanding of conditions necessary for habitability beyond our solar system.