Hubble finds planet with glowing water atmosphere

/hubble-finds-planet-glowing-water-atmos

  • Hubble finds planet with glowing water atmosphere | BBC Sky at Night Magazine
    http://www.skyatnightmagazine.com/news/hubble-finds-planet-glowing-water-atmosphere

    Scientists have discovered the strongest evidence to date for a stratosphere, a mid-level layer of atmosphere in which temperature increases with altitude, on a planet outside our Solar System, or exoplanet.

    The stratosphere was found around a hot Jupiter exoplanet, WASP-121b, using data taken by the Hubble Space Telescope.

    With a mass 1.2 times that of Jupiter and a radius about 1.9 times Jupiter’s, Hubble discovered that WASP-121b had high temperatures in its stratosphere relative to its lower atmosphere.

    This result is exciting because it shows that a common trait of most of the atmospheres in our solar system – a warm stratosphere – also can be found in exoplanet atmospheres,” said Mark Marley, study co-author based at NASA’s Ames Research Center.

    Reporting in the journal Nature, scientists were also able to determine that the exoplanet has an orbital period of a mere 1.3 days. This exoplanet is so close to its star that its outer atmosphere is heated to a blazing 2,500 °C, hot enough to boil lead.

    This super-hot exoplanet is going to be a benchmark for our atmospheric models,” said Hannah Wakeford, study co-author who worked on this research while at NASA’s Goddard Space Flight Center.

    • An ultrahot gas-giant exoplanet with a stratosphere : Nature : Nature Research
      http://www.nature.com/nature/journal/v548/n7665/full/nature23266.html

      Infrared radiation emitted from a planet contains information about the chemical composition and vertical temperature profile of its atmosphere. If upper layers are cooler than lower layers, molecular gases will produce absorption features in the planetary thermal spectrum. Conversely, if there is a stratosphere—where temperature increases with altitude—these molecular features will be observed in emission. It has been suggested that stratospheres could form in highly irradiated exoplanets, but the extent to which this occurs is unresolved both theoretically and observationally. A previous claim for the presence of a stratosphere remains open to question, owing to the challenges posed by the highly variable host star and the low spectral resolution of the measurements. Here we report a near-infrared thermal spectrum for the ultrahot gas giant WASP-121b, which has an equilibrium temperature of approximately 2,500 kelvin. Water is resolved in emission, providing a detection of an exoplanet stratosphere at 5σ confidence. These observations imply that a substantial fraction of incident stellar radiation is retained at high altitudes in the atmosphere, possibly by absorbing chemical species such as gaseous vanadium oxide and titanium oxide.