A research group using the James Webb Space Telescope found the signature of water vapor while analyzing a rocky planet. However, it is still unclear whether the track comes from the celestial body called GJ 486 b or from its star. The probability of both scenarios is “equally plausible,” explains the US space agency NASA. However, if the water vapor actually exists on the exoplanet, it would be the first time such a find has been made on a rocky planet. So far, water has only been found on gas planets without a solid surface. Given the immense heat that prevails on the celestial body, the water would have to be constantly replaced, the group writes. Volcanoes are therefore suitable for this.
Further analysis needed
Like the group around Sarah Moran from the University of Arizona explained, they used the NIRSpec instrument to target two so-called transits of GJ 486 b in front of its star. If the exoplanet has an atmosphere, bits of starlight would pass en route to us. Their traces can be found in a spectral analysis. In this case, the spectrum was mostly flat, but at the shortest infrared wavelengths, it had an “intriguing increase at the shortest infrared wavelengths.” Computer models had suggested that water vapor was the most likely cause. The measurements therefore match both water vapor on the exoplanet and an origin in the star itself.
Although most of the stars are much too hot for water vapour, it can occur in star spots. In comparison, it is very cool there. Even in the sunspots of our home star there is water vapor. Because the star GJ 486 is much cooler overall than our Sun, there could be many more of them in its patches. Although there is no evidence that such spots appeared on the side facing us during the transit of the exoplanet, it cannot be ruled out. The team is confident that further observations with the MIRI and NIRISS instruments can help clarify the precise origin of the water vapour.
If it actually occurs on the exoplanet, it would most likely have to be constantly renewed, the team explains. Because of the immense heat on the celestial body and the strong radiation of the star, it would otherwise be lost. GJ 486 b is said to be about 30 percent larger than Earth. It takes 1.5 earth days to orbit its red dwarf star, so it is very close. That’s why it’s not in the habitable zone, so water could only exist there as steam. It is therefore assumed that it is gravitationally bound and always turns the same side to its star. According to the team, the temperature on the surface is around 430 °C. The analysis is published in the Astrophysical Journal Letters.
(my)
