Exoplanets have sunsets too, although their color might be a bit offsetting

Ever wondered what a sunset (or rather, starset) will look like on an exoplanet? A new website, exoclimes.com, has been launched that "is devoted to discussion around the study of planetary atmospheres outside the Solar System":

Extrasolar planets orbit stars, in a similar way to the Earth orbiting the Sun. Professor Frédéric Pont of the University of Exeter has used the extrasolar planets' 'transmission spectrum', taken by the Hubble Space Telescope, to work out the colour of the 'sunsets' created by these stars.

Writing on the website exoclimes.com, where he has posted the two sunset images he has produced, Professor Pont said:  "Unlike its sister planet HD '189, the planet HD '209 ('Osiris') has a sunset that looks truly alien. The star is white outside the atmosphere, since its temperature is close to that of the Sun. It then acquires a bluish tinge as it sinks deeper, because the absorption by the broad wings of the neutral sodium lines (the spectral lines responsible for the gloomy orange of sodium street lighting) remove the red and orange from the star light.

"One key difference with a sunset on Earth is that the 'sun' is much larger from '209, because the planet is very close. Instead of changing colour as it moves near the horizon, the host star spans all colours at once."

The Science of Sunsets