Astronomers find blue planet outside solar system

LONDON — Astronomers have for the first time managed to determine the color of a planet outside our solar system, a blue gas giant 63 light-years away.

Using the Hubble Space Telescope, an international team said the planet known as HD 189733B would look like a deep blue dot if viewed up close.

"Measuring the planet's color is a real first — we have never managed it before with a planet outside our own solar system," Frederic Pont of the University of Exeter in England said Friday.

While Earth looks blue from space because of its oceans, the astronomers said the planet's color was created by a hazy turbulent atmosphere of silicate particles that scatter blue light. To determine the planet's color, the team measured the amount of light reflected off its surface as it passed behind its star.

Discovered in 2005, the planet belongs to a class of giant gas planets called "hot Jupiters" that orbit close to their stars. It has a daytime temperature of around 1,000 degrees Celsius (1,832 F), and the heat causes rocks to evaporate and glass to possibly rain sideways in howling 4,500 mph (about 7,250 kph) winds.

Astronomers chose the planet for observation because of its proximity to Earth and size in relation to the star it orbits. A light-year is nearly 6 trillion miles.

Pont said the technology the astronomers used pushed the Hubble telescope to its limit given the distance and light from other stars obscuring their view.

"People keep coming up with a better way of viewing planets indirectly so I'm sure the technology will eventually improve," Pont said.