Exoplanet close to star turns out to have much more water than thought dan

Astronomers have concluded that an exoplanet 700 light-years from Earth has much more water than previously thought. According to the researchers, this means that exoplanets can have very different compositions than the celestial bodies from our own solar system.

The researchers made this conclusion based on data from the Hubble and Spitzer space telescopes. The optical spectrum of the exoplanet WASP-39b has been mapped using spectrographs. It showed that there is a surprising amount of water in the atmosphere of this gas giant, which is comparable in size to Saturn. There would be three times as much water in the planet’s atmosphere as there is in Saturn.

This find is remarkable because WASP-39b orbits very closely around its star. The distance between the star and the exoplanet is only one-eighth the distance between our sun and Mercury, and the planet completes its orbit around the star in just four days. Due to its short distance, the planet is known as a ‘hot Saturn’, so it was not expected that relatively large amounts of water would be detected in the atmosphere. The planet has a so-called bound rotation; always the same side of the planet faces the star, so it can get about 750 degrees Celsius there.

The researchers had expected to find water vapor, but not in such quantities. Based on this, the astronomers concluded that there must be a large amount of heavier elements in the atmosphere. That means the planet was thought to have once been bombarded by icy material, which accumulated and remained in the atmosphere. According to the researchers, this was only possible if WASP-39b formed at a much greater distance from its star. The planet would thus have ‘migrated’ through the conscious planetary system. In the eyes of the astronomers, this means that the formation of planets is much more complex and confusing than previously believed.