Astronomers have been searching for years to find evidence of water in space. Despite all of that hard work, discovering that evidence has been incredibly tricky. Sure, we’ve discovered what could very well be a Martian water reservoir, and we’ve even found a cloud of water floating in deep space. But detecting water on exoplanets has been a bit more difficult.
That’s where telescopes like Hubble and James Webb come into play. In fact, while Webb has been giving us beautiful new observations of spiral galaxies for the PHANGS program, Hubble has been hard at work observing smaller exoplanets.
Now, the search for water in space has paid off in a new way, as Hubble has detected water vapor on the smallest exoplanet yet. This is — thus far, at least — the smallest exoplanet that we have discovered water vapor on. The team behind the discovery is currently looking at two possible theories to explain it.
First, it’s possible that the planet is a “mini-Neptune,” which would mean it has a hydrogen-rich atmosphere laced with water. The second possibility is that it is a warmer version of Europa, one of Jupiter’s moons, which contains twice as much water under its crust as the Earth does.
Either possibility is exciting and could explain why this tiny exoplanet, known as GJ 9827d, has shown evidence of water. This is also one of the first times that we have been able to detect the atmosphere of a planet this small, the researchers explain.
In their search for water in space, Hubble observed the planet during 11 transient events. This allowed researchers to see how the starlight from its star filtered through the atmosphere whenever it crossed in front of it. While it isn’t as exact as sending a probe into the planet’s atmosphere, for many of these distant exoplanets, this is the only way we have to try to discern what their atmospheres are made of.
Now, this Hubble discovery helps pave the way for a new record in the search for water in space. A record that will surely be broken as Webb and Hubble continue to scour the universe for new information that can help us better understand the world we live in.
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