Water detected on distant planet

Water has been detected for the first time in the atmosphere of a planet outside our Solar System.

The planet, known as HD 209458b, is a Jupiter-like gas giant located 150 light-years from Earth in the constellation Pegasus.

Other scientists reported in February they were unable to find evidence of water in this planet's atmosphere, as well as in another Jupiter-like planet.

Details of the research are published in the Astrophysical Journal.


Understanding the distribution of water in other solar systems is important for understanding whether or not conditions for life are possible
Travis Barman
Water vapour (or steam) was expected to be present in atmospheres of most known extrasolar planets, even those that orbit more closely to their parent star than Mercury is to our Sun.

For the majority of exoplanets, their close proximity to their parent star has made detecting water and other compounds difficult.

The identification reported here takes advantage of the fact that HD209458b, as seen from Earth, passes directly in front of its star every three and half days.

As a planet passes in front of a star, its atmosphere blocks a different amount of starlight at different wavelengths of light.

In particular, absorption by water in the atmosphere of a giant planet makes the planet appear larger across a specific part of the infrared spectrum compared to wavelengths in the visible spectrum.

http://news.bbc.co.uk/2/hi/science/nature/6544257.stm