Recently, a team of scientists discovered rocky clouds in the sky of a giant exoplanet 700 light-years distant from our earth. Using data from the James Webb Space Telescope (JWST), astronomers at Arizona State University, S. Mukherjee and his colleagues, found a huge gaseous planet dubbed WASP-94Ab. The researchers analyzed data from the JWST and concluded that the planet has a hazy morning sky and a clear evening sky.
Scientists did not suddenly find this hot exoplanet with the help of ordinary telescopes; in 2014, astronomers were searching for new exoplanets with the help of two robotic observatories located in the Canary Islands and South Africa. The project is known as the Wide Angle Search for Planets (WASP). During this time, with the help of the transit metho d, the researchers found this exoplanet, WASP-94A b. What is the transit method? When a planet passes in front of its star, the star’s light intensity decreases slightly for a period of time; in fact, the star’s light reaches JWST through the various gases and water vapors in the planet’s atmosphere.
By analyzing this change in light, scientists realized the existence of the exoplanet. At that time, they noticed that two stars in its vicinity (WASP-94A and WASP-94B) were orbiting each other; that is, it was actually part of a ‘binary star system.’ Scientists have found more than 6,000 exoplanets to date, including WASP-94Ab. The exoplanet orbits the star WASP-94A and is just a bit bigger than Jupiter (1.58 times Jupiter’s radius). It completes a full rotation around the star in just 4 Earth days. One side of the globe always faces the stars; hence, one side has permanent day, and the other side has permanent darkness.
James Webb has now provided researchers with the image of this bright and dark edge. The star’s light flows through the planet’s atmosphere and different chemical elements absorb different wavelengths of light. The consequence is that the radiant and dark zones have different spectra, which is indisputable in the research of exoplanets. While studying the cloud cycle of this strange exoplanet, scientists have found that the weather here is quite extreme; it is cloudy in the morning and clear in the evening. This extreme contrast of weather is what makes the planet attractive to astronomers.
Instead of water vapor, the clouds contain rock-forming minerals such as magnesium silicate, iron, and magnesium sulfide; for this reason, researchers call them ro cky clouds. The night temperature here is about 450 Kelvin lower than during the day, so when the cool night air enters the daylight, thick rocky clouds appear in the sky. Again, due to its close proximity to the star, WASP-94A b has a hot atmosphere; during the day, its surface temperature exceeds 1,200 K. At this time, the sky is bright and clear in the afternoon; due to the intense heat, thick rocky clouds evaporate and mix with the air.
Prior to the JWST, scientists utilized the Hubble Space Telescope to look out into space. At the time, the data indicated that the planet was rich in carbon and oxygen (several hundred times that of Jupiter). By examining James Webb’s data, scientists have now discovered that the previous conclusion was incorrect. Researchers hadn’t identified the true cause of the planet’s rocky cloud shadow at the time. Later, research on the cloud’s composition revealed it had five times as much carbon and oxygen as Jupiter would on a typical gaseous planet.
In reality, previous examination of Hubble data had produced an average image of the planet’s atmosphere, but in the current study, different spatial views are readily available, and scientists have long recognized that spatial data is more fruitful than statistical averages in producing an accurate picture. Mukherjee and his colleagues’ work are believed to be helpful in comprehending the climate of distant exoplanets. In fact, the most popular question in exoplanet research is what elements those planets are made of, and therefore, researchers have no choice but to analyze the cloud dynamics. Now the question is—is this strange cloud cycle only seen on WASP-94A b, or are there more such exoplanets orbiting in space? Therefore, more research is needed in this area. Hopefully, James Webb will not disappoint future researchers.
(THE AUTHOR IS A RESEARCHER AND FREELANCE SCIENCE WRITER)