NASA's iconic Hubble Space Telescope has been used by researchers to identify an exoplanet lurking outside of our solar system that has been described as a "landmark discovery".
The European Space Agency (ESA) and NASA posted to their websites announcing the discovery of an exoplanet located 97 light-years from Earth in the constellation Pisces. The exoplanet is called GJ 9827d and was first discovered by NASA's Kepler Space Telescope in 2017, but now astronomers have pointed Hubble's instruments at exoplanet and detected water vapor.
While this isn't the first exoplanet that astronomers have detected water vapor, it is the smallest at only approximately twice Earth's diameter. Prior to this discovery, water vapor had gone undetected on small planets, and NASA believes that GJ 9827d could be an example of water-rich planets being present elsewhere in our galaxy.
However, it's still too early to determine if Hubble's instruments detected a small amount of water vapor in the planet's atmosphere or if the planet's atmosphere is mostly made of water.
"Water on a planet this small is a landmark discovery," added co-principal investigator Laura Kreidberg of Max Planck Institute for Astronomy in Heidelberg, Germany. "It pushes closer than ever to characterizing truly Earth-like worlds."
The team behind the discovery has come up with two possibilities: the planet is either a hydrogen-rich atmosphere laced with water, which would mean that GJ 9827d is a mini-Neptune, or it's more similar to Jupiter's moon Europa but much warmer with massive water deposits beneath its surface.
"Until now, we had not been able to directly detect the atmosphere of such a small planet. And we're slowly getting in this regime now," added Benneke. "At some point, as we study smaller planets, there must be a transition where there's no more hydrogen on these small worlds, and they have atmospheres more like Venus (which is dominated by carbon dioxide)."