[billforsternz]

I picked up a random book in the science section of the city library today and opening it to a random page I started reading about an exciting "goldilocks" exoplanet discovery from 2015. Apparently this was the first exo-planet which had a positive spectroscopic identification of water in the atmosphere. It was a rocky world, 2 billion years old, 8 times Earth's size (mass?), on a 33 day orbit around a red dwarf. K-something-or-other. The book said the really exciting discoveries will happen when Webb comes online in 2021. The link is down, but someone mentions this planet is 8 x Earth size down thread. I wonder if it's the same planet?

[stevenwoo]

Maybe you mixed up the dates slightly?

K2-18b (name of the exo-planet) orbiting star K2-18 was discovered in 2015 but the water was not detected until 2019.

[billforsternz]

Sorry, didn't notice the reply in a timely way. I went back to the library, the book was "The Universe" by Andrew Cohen. It was indeed K2-18B, discovered by Kepler in 2015. It says that the water was discovered by Hubble later, so presumably 2019.

[truculent]

I think this is supposedly a Hycean (ocean + hydrogen atmosphere) planet, rather than rocky. Unless those categories aren’t exclusive.

[billforsternz]

Sorry, didn't notice this in a timely way. I went back to the library to check, and indeed the planet I was reading about was K2-18b. The book at least says that K2-18b is a Super-Earth and will almost certainly have a molten rocky core.