First color detected for planet outside our system
Astronomers using NASA’s Hubble Space Telescope say they have figured out the color of a planet outside our solar system for the first time.
It’s cobalt blue, though not at all Earth-like, they said, describing a world where surface temperatures are hot enough to melt stone and where it may rain glass—sideways. The planet is HD 189733b, one of the closest worlds outside our solar system visible crossing the face of its star, 63 light-years away. A light-year is the distance light travels in a year.
Hubble’s Space Telescope Imaging Spectrograph, which analyzes light, measured changes in color coming from the planet’s location before, during and after a pass behind its star. There was a slight drop in light and color change, scientists said.
“Light was missing in the blue [part of the spectrum] but not in the red when it was hidden,” explained research team member Frederic Pont of the University of Exeter in South West England. So “the object that disappeared was blue.”
Earlier observations had reported evidence for scattering of blue light on the planet. The latest work would confirm that. On this turbulent alien world, scientists say, the daytime temperature is nearly 2,000 degrees Fahrenheit (1,100 Celsius), and it possibly rains glass sideways in howling, 4,500-mph (7,200-kph) winds.
The cobalt blue comes not from the reflection of a tropical ocean as it does on Earth, they add, but rather a hazy, blow-torched atmosphere containing high clouds laced with silicate particles. Silicates condensing in the heat could form very small drops of glass that scatter blue light more than red light.
Hubble and other observatories have intensively studied HD 189733b and found its atmosphere to be changeable and exotic.
It’s among a bizarre class of planets called hot Jupiters, which circle precariously close to their parent stars. The new observations yield new insights into the makeup and cloud structure of the whole class, according to investigators. The planet was first identified in 2005 and orbits an estimated 2.9 million miles (4.6 million km) from its parent star, so close that it’s tidally locked—the same side always faces the star.
In 2007, NASA’s Spitzer Space Telescope measured the infrared light, or heat, from the planet, leading to one of the first temperature maps for planet outside our system. The map shows day side and night side temperatures on HD 189733b differ by about 500 degrees Fahrenheit (280 Celsius). This is expected to cause fierce winds to roar from the day side to the night side.
PHOTO: Artist’s impression of HD 189733b (Courtesy NASA, ESA, and G. Bacon (STScI))
For more on this story go to:
http://www.world-science.net/othernews/130712_blueplanet.htm