Hubble Spots Azure Blue Planet where it Rains Glass
Astronomers using the NASA/ESA Hubble Space Telescope have, for the first time, determined the true colour of a planet orbiting another star. If seen up close this planet, known as HD 189733b, would be a deep cobalt blue, reminiscent of Earth’s colour as seen from space.
But that’s where the similarities end. This “deep blue dot” is a huge gas giant orbiting very close to its host star. The planet’s atmosphere is scorching with a temperature of over 1000 degrees Celsius, and it rains glass, sideways, in howling 7000 kilometre-per-hour winds.
At a distance of 63 light-years from us, this turbulent alien world is one of the nearest exoplanets to Earth that can be seen crossing the face of its star. It has been intensively studied by Hubble and other telescopes, and its atmosphere has been found to be dramatically changeable and exotic, with hazes and violent flares (heic0720, heic1209). Now, this planet is the subject of an important first: the first measurement of an exoplanet’s visible colour.