# K2-18b: First detection of water vapor in the atmosphere of an exoplanet in the habitable zone **URL:** \ **Category:** Miscellaneous and Personal Stuff I Must Share\ **Created:** [September 13, 2019, 9:43am UTC](https://boards.straightdope.com/t/k2-18b-first-detection-of-water-vapor-in-the-atmosphere-of-an-exoplanet-in-the-habitable-zone/840159 "2019-09-13T09:43:32Z")\ **Posts on this page:** 3\ **Page:** 1
**Author:** ![JoseB](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/joseb/32/1530_2.png) [@JoseB](https://boards.straightdope.com/u/JoseB)\ **Post date:** [September 13, 2019, 9:43am UTC](https://boards.straightdope.com/t/k2-18b-first-detection-of-water-vapor-in-the-atmosphere-of-an-exoplanet-in-the-habitable-zone/840159/1 "2019-09-13T09:43:32Z")
Exoplanet K2-18b was discovered during the “second light” mission of the Kepler space telescope. The star K2-18 is located about 124 light years from us, in the constellation of Leo. Two independent studies, examining data from Kepler and the Hubble and Spitzer space telescopes, have concluded that there are significant amounts of water vapor in its atmosphere. This is the first time that water vapor is detected in the atmosphere of a planet orbiting within the habitable zone of its star. The star is a red dwarf, and the planet orbits it once every 33 days. It is very likely that the planet is tidally locked to its star. This is (in my opinion) quite an important discovery. Opinions? Links: > **[Water Vapor and Clouds on the Habitable-Zone Sub-Neptune Exoplanet K2-18b](https://arxiv.org/abs/1909.04642)** > > Results from the Kepler mission indicate that the occurrence rate of small > planets ($\<3$ $R\_\\oplus$) in the habitable zone of nearby low-mass stars may be > as high as 80%. Despite this abundance, probing the conditions and atmospheric > properties on... (abstract of the paper that discloses water vapor in the atmosphere of K2-18b; submitted on September 10). > **[The Water Vapor Find on 'Habitable' Exoplanet K2-18 b Is Exciting — But It's...](https://www.space.com/alien-planet-k2-18b-water-vapor-not-earth-twin.html)** > > But who says the confirmation of alien life will come on Earth 2.0? [https://www.nature.com/articles/s41550-019-0878-9](https://www.nature.com/articles/s41550-019-0878-9) Also, it is interesting to note that the system of star K2-18 seems to have yet another planet in it, K2-18c, orbiting closer to the star but _ **not** _ in the same plane as K2-18b. However, it appears that the system is so far stable. Link: > **[Characterization of the K2-18 multi-planetary system with HARPS. A habitable...](https://ui.adsabs.harvard.edu/abs/2017A%26A...608A..35C/abstract)** > > Aims: The bright M2.5 dwarf K2-18 (Ms = 0.36 M⊙, Rs = 0.41 R⊙) at 34 pc is known to host a transiting super-Earth-sized planet orbiting within the star's habitable zone; K2-18b. Given the superlative nature of this system for studying an exoplanetary... All in all, QUITE interesting and exciting findings! ---
**Author:** ![Ponderoid](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/ponderoid/32/19221_2.png) [@Ponderoid](https://boards.straightdope.com/u/Ponderoid)\ **Post date:** [September 13, 2019, 1:17pm UTC](https://boards.straightdope.com/t/k2-18b-first-detection-of-water-vapor-in-the-atmosphere-of-an-exoplanet-in-the-habitable-zone/840159/2 "2019-09-13T13:17:20Z")
Scott Manley just posted a video about it, [Water Found On Distant 'Super Earth' (or Mini Neptune) AND A New Interstellar Comet! - YouTube](https://www.youtube.com/watch?v=OG38Ei8R_08) He says this “[…] shouldn’t be taken as some sign that it’s habitable, because the planet is so large it likely has a thick crushing atmosphere at its surface […]” (from the video description) ---
**Author:** ![Darren\_Garrison](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/darren_garrison/32/92_2.png) [@Darren\_Garrison](https://boards.straightdope.com/u/Darren_Garrison)\ **Post date:** [September 13, 2019, 3:27pm UTC](https://boards.straightdope.com/t/k2-18b-first-detection-of-water-vapor-in-the-atmosphere-of-an-exoplanet-in-the-habitable-zone/840159/3 "2019-09-13T15:27:59Z")
A nice technical achievement, measuring the atmosphere like that, but nothing suprising. Probably pretty much all super-Earths that aren’t boilingly close to their primary are [water worlds](https://earthsky.org/space/water-worlds-exoplanets-likely-common-alien-life). Water is very, very common. In fact, the Earth likely has far less water than normal (probably because of the whole Theia thing.) But that very “practically being a desert planet” thing was probably [a huge stroke of good luck](https://manyworlds.space/2017/11/22/can-you-overwater-a-planet/).