2024-04-12 15:35:24
WASP-76b is one of the frequently studied exoplanets. It has extremely high temperatures and metal rain on its far side. Astronomers mostly have impressions of it as harsh, chaotic, and hellish. However, recent new observational data shows that it may have a rainbow-like optical phenomenon that has only been observed on Earth and Venus.
Every time WASP-76b is explored, astronomers find it weirder. This exoplanet is 637 light-years away from us and orbits a star that is 50% more massive than the sun and 500°C hotter than the sun. Because it is tidally locked by the star, one side of the planet always faces the scorching sunlight, and the atmosphere on the sun-facing side is Heated to 2,000°C, the temperature is high enough to evaporate metallic iron and lead.
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However, on the backside where there is never any light, the temperature immediately drops to about 1,500°C. The extreme temperature difference creates strong winds with a speed of more than 16,000 kilometers per hour. At the same time, the iron vapor condenses to form iron clouds, and molten iron rain drops from the sky. Such a strange scene makes WASP Since its discovery in 2013, -76b has become one of the objects of interest for astronomers.
▲ WASP-76b is an imaginary picture of iron rain falling on the sunny side. (Source:European Space Agency）
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Recently, new phenomena have been discovered in observation data from the European Space Agency’s Cheops satellite and NASA’s Transiting Exoplanet Survey Satellite (TESS).
When light passes through water droplets in clouds or fog, it will produce concentric ring optical effects that look similar to rainbows (actually quite different from rainbows), and 23 observations by the Cheops satellite over 3 years have shown that the bright and dark boundaries of WASP-76b (the sunward side and the There is an astonishing increase in the amount of light at the intersection of the back and the sun. Scientists believe that this luminosity is caused by a halo effect caused by strong, localized, anisotropic reflection.
We have never seen a halo outside the solar system, because it needs to meet very special conditions. First, it must have nearly perfectly spherical (uniform and stable) atmospheric particles; second, the parent star needs to directly illuminate the planet; third, observation The viewer must be in the right direction to see this wonderful light.
The halo effect was found in WASP-76b, indicating that there are clouds composed of perfectly spherical water droplets in the atmosphere, and that these water droplets have persisted for at least 3 years or need to be continuously replenished. In order for such clouds to persist, the atmospheric temperature needs to remain stable over time, suggesting that WASP-76b, which has long been considered turbulent and chaotic, is actually relatively peaceful.
In the future, the NIRSPEC instrument of the Webb Space Telescope will be put into follow-up observations to further verify whether the fascinating “extra light” of WASP-76b is a rare halo effect.
new paperPublished in Astronomy & Astrophysics.
(Source of first picture:European Space Agency）
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