British astronomers have for the first time been able to determine the color of exoplanets. Using the Hubble Telescope, researchers from the University of Oxford conducted a spectral analysis of a star in the constellation Vulpecula and were able to calculate the color of the orbiting planet HD 189733 b. Details with reference to an unpublished article by scientists for the journal Astrophysical Journal Letters are provided by Nature News .

Since the star is located too far, 63 light years from Earth, it is impossible to photograph it even with one of the best telescopes of our time. However, Hubble's spectrometers allowed the researchers to obtain two spectra: at the moment when the planet is hidden from observation by the star and at the moment when it is in the visible zone. By comparing these spectra with each other, scientists were able to determine its optical properties and, in particular, draw a conclusion about the blue color of its atmosphere.

The blue-colored planet is uninhabited. It belongs to the class of so-called hot Jupiters: previous observations showed that HD 189733 b orbits the star in just two days, and its surface is heated to almost eight hundred degrees Celsius. Scientists explain the blue color by the presence of a continuous cloud layer in the lower layers of the atmosphere: and this mechanism differs from the one that is responsible for the blue color of the known planets of the solar system.

Clouds reflect all rays in approximately equal proportions, and if they were in the upper atmosphere, then HD 189733 would be white. But due to its location at lower altitudes, light additionally passes through the sodium-rich atmosphere, which absorbs yellow light, leaving only blue rays: the reflective layer of clouds is wrapped in an additional light filter. Earth is blue because of its liquid ocean, and Neptune is blue because of the methane in its atmosphere, but HD 189733 is different from all previously known celestial bodies.

Despite the fact that the number of discovered exoplanets is approaching a thousand, direct determination of their color is difficult due to large distances and the lack of sufficiently powerful telescopes. Scientists have repeatedly been able to conduct spectral analyzes of the atmosphere of exoplanets, isolating their light from the light of a star, but these studies were carried out in the infrared range, without answering the question about the color of the celestial body.

Astronomers have found the first blue exoplanet