Water detected on planet HD209458b — First evidence of atmospheric water ever found outside our solar system

In a report to be published in the Astrophysical Journal, astronomer Travis Barman, from the Lowell Observatory in Flagstaff, Arizona, cites strong evidence for water in the atmosphere of HD209458b, located some 150 million light-years away from Earth. (One light-year = 5.9 trillion miles).

Above, a drawing of the planet, whose clouds appear to contain steam, orbiting its star.

Here's a link to last week's BBC story; this will take you to a report in Scientific American.

Here's coverage from space.com.

All warmed up?

Good, 'cause here's the Astrophysical Journal report's abstract.

Identification of Absorption Features in an Extrasolar Planet Atmosphere

Water absorption is identified in the atmosphere of HD209458b by comparing models for the planet's transmitted spectrum to recent, multi-wavelength, eclipse-depth measurements (from 0.3 to 1 microns) published by Knutson et al. (2007). A cloud-free model which includes solar abundances, rainout of condensates, and photoionization of sodium and potassium is in good agreement with the entire set of eclipse-depth measurements from the ultraviolet to near-infrared. Constraints are placed on condensate removal by gravitational settling, the bulk metallicity, and the redistribution of absorbed stellar flux. Comparisons are also made to the Charbonneau et al. (2002) sodium measurements.