An unusually colorful optical phenomenon – a halo or halo – in Earth’s clouds has been visible for the first time in the atmosphere of a distant alien world. So far this is only a possibility, but it is large enough to continue studying this phenomenon. If the data is confirmed, the discovery will allow us to learn more about the atmospheres of exoplanets and even the oceans on their surfaces. This is an invaluable opportunity to examine the worlds to which humanity will arrive very, very soon.

Scientists from the Portuguese Institute of Astrophysics and Space Sciences discovered signatures of the halo in archival data of exoplanet WASP-76b from the CHEOPS, TESS, Hubble and Spitzer observatories. This is the extremely hot Jupiter, which has repeatedly become the focus of astronomers’ attention. This planet orbits an F7 class star with a mass of 1.4 solar masses and an age of 2.4 billion years. The application period is only 1.8 days. This means that the planet is literally bathed in the star’s powerful energy radiation.

Temperatures reach 2400°C on the sunny side of WASP-76b (always with one side facing the sun). This type of heating evaporates metals from the surface and turns them into steam. It’s hard to imagine, but the showers in WASP-76b are composed of droplets of molten metal, primarily iron, as spectral measurements show. The halo features are ultimately the result of light from the local star being refracted on clouds of nearly identical molten iron droplets in the exoplanet’s upper layers.

Data on a possible and characteristic optical phenomenon were obtained more than two dozen times. It was observed when the outer planet, called a secondary eclipse, passed behind its star (the system is 640 light-years away from us). In optics the planet suddenly became brighter, while in infrared light the intensity remained unchanged. It cannot be excluded that other processes may occur in the atmosphere of WASP-76b, accompanied by the observed data set. That’s why scientists will continue to observe WASP-76b because it’s a chance to understand how we can interpret atmospheric and even surface events on other worlds.