Today, we are going to visit WASP-39 b a gas giant planet that orbits a Sun-like star 700 light-years away.
WASP-39 b is a hot and puffy planet with a mass roughly one-quarter that of Jupiter and a diameter 1.3 times greater than Jupiter. Its extreme puffiness is related in part to its high temperature of about 1,600 degrees Fahrenheit or 900 degrees Celsius. Unlike the cooler, more compact gas giants in our solar system, WASP-39 b orbits very close to its star – only about one-eighth the distance between the Sun and Mercury – completing one circuit in just over four Earth-days.
Because it is so close to its host star, it is likely to be tidally locked, which means one side of the planet faces the star at all times.
WASP-39 b was discovered in 2011 based on ground-based detections of the subtle, periodic dimming of light from its host star as the planet transits, or passes in front of the star. Since then, it has been studied by various telescopes, including NASA’s Hubble and Spitzer space telescopes, which revealed the presence of water vapor, sodium, and potassium in the planet’s atmosphere.
But the most exciting discovery came in July 2022, when WASP-39 b became the first exoplanet to be studied by NASA’s James Webb Space Telescope. The Webb Space Telescope captured the first clear evidence for carbon dioxide in the atmosphere of a planet outside the solar system. This observation provides important insights into the composition and formation of the planet. In November 2022, five science papers reported on WASP-39 b discoveries made using JWST. Those included the first observation of sulfur dioxide and photochemistry (chemical changes influenced by starlight) in an exoplanet atmosphere.
WASP-39 b is a fascinating example of how diverse and complex exoplanets can be. By studying its atmosphere with Webb, we can learn more about how this planet formed and evolved, and how it compares to other gas giants in our galaxy. WASP-39 b is also a promising target for future observations with Webb, which may be able to detect and measure carbon dioxide in the thinner atmospheres of smaller rocky planets.