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How the sun sets in an alien world

Scientists have thrown light on how sunsets on exoplanets would look like. According to an exoplanetary scientist, a world 150 light-years from Earth, orbits extremely close to its star, atmospheric temperatures are high (around 1,000 degrees Celsius).

india Updated: Jan 11, 2012 12:42 IST

Scientists have thrown light on how sunsets on exoplanets would look like.

According to University of Exeter exoplanetary scientist Frederic Pont, as exoplanet planet HD 209458 b - unofficially known as “Osiris”, a world 150 light-years from Earth, orbits extremely close to its star, atmospheric temperatures are high (around 1,000 degrees Celsius or 1,800 degrees Fahrenheit).

This implies that its outer atmospheric layers become “puffed up.”

The exoplanet’s atmospheric “puffiness” makes it easier to analyze, and using data from the STIS spectrograph on the Hubble Space Telescope, Pont was able to calculate how the star would look as seen at the exoplanet’s horizon, Discovery News reported.

In the case of Osiris, as its star drops through the atmosphere from an observer’s perspective, it will transform from predominantly white to blue.

The blueness is due to atmospheric sodium absorbing the orange/red light being emitted by the star, causing its light to shift towards the blue part of the spectrum.

As the star drops further, Rayleigh scattering by atmospheric molecules will disperse even the blue light from the star. (Rayleigh scattering is the same mechanism that gives Earth''s sky a blue hue.)

The only light able to make it through the atmosphere will be green and ultimately murky brown. The atmosphere will then glow because of emission from atmospheric molecules and the Rayleigh scattering will cause a blue hue to stay on.