Water vapour in the atmosphere of the habitable-zone eight-Earth-mass planet K2-18 b

  title={Water vapour in the atmosphere of the habitable-zone eight-Earth-mass planet K2-18 b},
  author={Angelos Tsiaras and Ingo P. Waldmann and Giovanna Tinetti and Jonathan Tennyson and Sergey N. Yurchenko},
  journal={Nature Astronomy},
In the past decade, observations from space and the ground have found water to be the most abundant molecular species, after hydrogen, in the atmospheres of hot, gaseous extrasolar planets1–5. Being the main molecular carrier of oxygen, water is a tracer of the origin and the evolution mechanisms of planets. For temperate, terrestrial planets, the presence of water is of great importance as an indicator of habitable conditions. Being small and relatively cold, these planets and their… 

Water Vapor and Clouds on the Habitable-zone Sub-Neptune Exoplanet K2-18b

Results from the Kepler mission indicate that the occurrence rate of small planets (<3 R⊕) in the habitable zone of nearby low-mass stars may be as high as 80%. Despite this abundance, probing the

Hydrodynamic Escape of Water Vapor Atmospheres near Very Active Stars

When exposed to the high-energy X-ray and ultraviolet radiation of a very active star, water vapor in the upper atmospheres of planets can be photodissociated and rapidly lost to space. In this

Atmospheric regimes and trends on exoplanets and brown dwarfs

  • Xi Zhang
  • Physics, Geology
    Research in Astronomy and Astrophysics
  • 2020
A planetary atmosphere is the outer gas layer of a planet. Besides its scientific significance among the first and most accessible planetary layers observed from space, it is closely connected with

Distinguishing between Wet and Dry Atmospheres of TRAPPIST-1 e and f

The nearby TRAPPIST-1 planetary system is an exciting target for characterizing the atmospheres of terrestrial planets. The planets e, f, and g lie in the circumstellar habitable zone and could

KELT-11 b: Abundances of Water and Constraints on Carbon-bearing Molecules from the Hubble Transmission Spectrum

In the past decade, the analysis of exoplanet atmospheric spectra has revealed the presence of water vapor in almost all the planets observed, with the exception of a fraction of overcast planets.

Clouds will Likely Prevent the Detection of Water Vapor in JWST Transmission Spectra of Terrestrial Exoplanets

We are on the verge of characterizing the atmospheres of terrestrial exoplanets in the habitable zones of M dwarf stars. Due to their large planet-to-star radius ratios and higher frequency of

The Nature and Origins of Sub‐Neptune Size Planets

Results from NASA's Kepler mission have revealed a bimodality in the radius distribution of sub‐Neptune planets, with a relative underabundance of planets between 1.5 and 2.0 R⊕, which suggests that sub-Neptunes are mostly rocky planets that were born with primary atmospheres a few percent by mass accreted from the protoplanetary nebula.

Methane as a dominant absorber in the habitable-zone sub-Neptune K2-18 b

In their Letter, Tsiaras et al.$^1$ reported the detection of water vapour in the atmosphere of K2-18 b, an exoplanet of 7 to 10 Earth masses located in the habitable zone of an M-dwarf star. The

The Interior and Atmosphere of the Habitable-zone Exoplanet K2-18b

Exoplanets orbiting M-dwarfs present a valuable opportunity for their detection and atmospheric characterization. This is evident from recent inferences of H2O in such atmospheres, including that of

Nondetection of Helium in the Upper Atmospheres of Three Sub-Neptune Exoplanets

We present a search for helium in the upper atmospheres of three sub-Neptune-sized planets to investigate the origins of these ubiquitous objects. The detection of helium for a low-density planet



Atmospheric reconnaissance of the habitable-zone Earth-sized planets orbiting TRAPPIST-1

Seven temperate Earth-sized exoplanets readily amenable for atmospheric studies transit the nearby ultracool dwarf star TRAPPIST-1 (refs 1,2). Their atmospheric regime is unknown and could range from

Strong water absorption in the dayside emission spectrum of the planet HD 189733b

The detection of strong water absorption in a high-signal-to-noise, mid-infrared emission spectrum of the planet itself is reported, finding both a strong downturn in the flux ratio below 10 µm and discrete spectral features that are characteristic of strong absorption by water vapour.

Infrared transmission spectra for extrasolar giant planets

Among the hot Jupiters known to date that transit their parent stars, the two best candidates to be observed with transmission spectroscopy in the mid-infrared (MIR) are HD 189733b and HD 209458b,

A Detection of Water in the Transmission Spectrum of the Hot Jupiter WASP-12b and Implications for its Atmospheric Composition

Detailed characterization of exoplanets has begun to yield measurements of their atmospheric properties that constrain the planets’ origins and evolution. For example, past observations of the

A Population Study of Gaseous Exoplanets

We present here the analysis of 30 gaseous extrasolar planets, with temperatures between 600 and 2400 K and radii between 0.35 and 1.9 RJup. The quality of the HST/WFC3 spatially scanned data

Water vapour absorption in the clear atmosphere of a Neptune-sized exoplanet

Observations of the transmission spectrum of the exoplanet HAT-P-11b from the optical wavelength range to the infrared indicate that the planetary atmosphere is predominantly clear down to an altitude corresponding to about 1 millibar, and sufficiently rich in hydrogen to have a large scale height.


Recent results from the Kepler mission indicate that super-Earths (planets with masses between 1–10 times that of the Earth) are the most common kind of planet around nearby Sun-like stars. These


Because of their large numbers, low-mass stars may be the most abundant planet hosts in our Galaxy. Furthermore, terrestrial planets in the habitable zones (HZs) around M-dwarfs can potentially be


The recent detections of two transit events attributed to the super-Earth candidate K2-18b have provided the unprecedented prospect of spectroscopically studying a habitable-zone planet outside the

Disentangling the Planet from the Star in Late-Type M Dwarfs: A Case Study of TRAPPIST-1g

The atmospheres of late M stars represent a significant challenge in the characterization of any transiting exoplanets because of the presence of strong molecular features in the stellar atmosphere.