According to a July 11 news release from NASA’s Goddard Space Flight Center (GSFC), astronomers using the space agency’s Hubble Space Telescope to make visible-light observations of exoplanet HD 189733b have concluded that the true color of the celestial body is blue. The exoplanet orbits a star (HD 189733b) 63 light-years from Earth, and according to NASA scientists, it is one of the closest exoplanets that can be observed crossing the face of its parent star.
The Imaging Spectrograph onboard the Hubble Space Telescope observed and measured the changes in the color of the light from the planet before, during, and after it passed behind its parent star. Due to changes in light intensity and a slight change in color, the astronomers built a solid case for concluding what color the planet actually is.
According to Frederic Pont, a team researcher from the University of Exeter in South West England, “This planet has been studied well in the past, both by ourselves and other teams. But measuring its color is a real first — we can actually imagine what this planet would look like if we were able to look at it directly.”
The conclusion offered firm evidence to back up previous observations of the planet, which reported evidence of scattering of blue light on the planet. Though the deep blue color of the dot is reminiscent of Earth, there was little comparison between the habitability of our planet and that of HD 189733b.
The atmosphere on HD 189733b is not tranquil; the average daylight temperature is 2,000 degrees Fahrenheit, the average nighttime temperature is 500 degrees Fahrenheit, and the precipitation is possibly glass droplets, which fly around the atmosphere sideways in hypersonic winds – created by the enormous diurnal temperature shift of 4,500 miles per hour. The deep blue color comes from the reflection of sunlight off silicate particles laced within high altitude clouds in the atmosphere. Astronomers contend that the condensation of silicates in the hot atmosphere could create tiny drops of glass that primarily scatter blue, rather than red light.
HD 189733b has the distinction of being among a peculiar class of planets called “hot Jupiters,” which orbit perilously close to their parent stars. HD 189733b, discovered in 2005, is positioned 2.9 million miles from its parent star. Akin to the relationship between Earth and our moon, the exoplanet and its star are gravitationally locked, and only one side of the exoplanet is bathed in sunlight.
“It’s difficult to know exactly what causes the color of a planet’s atmosphere, even for planets in the Solar System,” noted Pont. “But these new observations add another piece to the puzzle over the nature and atmosphere of HD 189733b. We are slowly painting a more complete picture of this exotic planet.”