“Hubble” found water vapor in the atmosphere of the exoplanet GJ 9827d
The Hubble Space Telescope detected water vapor in the atmosphere of the exoplanet GJ 9827d, located 97 light years from Earth. This is the smallest exoplanet of all, where water was discovered – it is twice the size of the Earth in diameter. At the same time, the planet is as hot as Venus (about 800 °F or 426 °C).
“Hubble” observed the exoplanet for three years using the transit method – when the object passes in front of the star from the observer’s side. Thus, the telescope was able to obtain spectral data of the planet’s atmosphere. Different elements absorb light in different ways, thanks to which the approximate composition of the atmosphere can be determined.
At the moment, researchers hypothesize two possibilities: water is found in the hydrogen-rich atmosphere of GJ 9827d, or the atmosphere is mostly water. In the first case, as the researchers note, the exoplanet can be compared to a mini-Neptune, in the second – to a hot version of Europa, a satellite of Jupiter. In any case, it will be a landmark discovery. If the water-dominated version is confirmed, it is likely that GJ 9827d was further away from its star and not as hot as it is now when it formed.
The results of the observations are published in open access to the article “Water absorption in the transmission spectrum of the water-world candidate GJ 9827d» on arXiv.