Do rainbows exist in distant worlds? Many phenomena that occur on Earth, such as rain, hurricanes, and aurora borealis, can also occur on other planets in the solar system if conditions are right. Now there’s evidence from outside our solar system that a particularly bizarre exoplanet may even exhibit something akin to a rainbow.
Glory, a phenomenon that appears as a colored halo in the sky, occurs when light hits a cloud made of homogeneous material in the form of spherical water droplets. This may explain the mystery surrounding the observation of exoplanet WASP-76B. The planet is a scorching gas giant that experiences rain of molten iron, and there is also more light in the eastern terminator (the line used to separate the day and night sides) than in the western terminator. being observed. Why was there more light on one side of the Earth?
A research team from ESA and the University of Bern in Switzerland observed it with the CHEOPS space telescope and combined it with previous observations by Hubble, Spitzer and TESS and found that the most likely reason for the extra light is Glory. That’s what I think. .
see the light
CHEOPS made 23 observations of WASP-76B in both visible and infrared light over a three-year period.These include: phase curvetransit, and secondary solar eclipse. A phase curve is a continuous observation that tracks a planet’s complete revolution and shows changes in its phase, or the portion of its illuminated surface facing the telescope. As a planet orbits its star, a telescope may be able to see more or less of its side. Phase curves can determine the overall brightness changes of planets and stars as they orbit.
A secondary eclipse occurs when a planet passes behind its host star and is eclipsed by the host star. The light seen during such an eclipse can later be compared to the total light before and after the eclipse to get a sense of the light reflected from the planet. Hot Jupiters like WASP-76B are often observed through secondary eclipses.
Observation of the phase curve can continue even while the planet is eclipsing the star. While observing the phase curve of WASP-76B, CHEOPS observed an excess of pre-eclipse light on the night side. This was also seen in previous observations of TESS phase curves and secondary solar eclipses.
The end of the rainbow?
The advantage of WASP-76b is that it is an ultra-hot Jupiter, so at least on its dayside it is free of the clouds and fog that often obscure the cool, hot Jupiter’s atmosphere. This makes it much easier to detect emissions into the atmosphere. The asymmetry in iron content between dayside and nightside terminators had already been observed. previous research, this planet became particularly interesting. There was less gaseous iron in the upper atmosphere on the dayside edge than on the nightside edge. This is probably because iron rain falls on the day side of WASP-76b and condenses into an iron cloud on the night side.
Hubble’s observations suggested that a thermal inversion (when the air near the planet’s surface begins to cool) is occurring on the night side. As that side cools, the iron that previously evaporated in the intense heat condenses again, condensing into clouds and raining on the day side. Droplets of liquid iron can form clouds.
These clouds are very important because light from the host star can reflect off the cloud droplets, creating a glorious effect.
“Using the glory effect to explain the observations would require highly reflective spherical aerosols or cloud spherical droplets in the Earth’s eastern hemisphere,” the researchers wrote recently in Astronomy & Astrophysics. This is stated in a paper published in .
Glory has been witnessed off-world before. They are also known to form in clouds. Venus. Similar to WASP-76b, more pre-eclipse light was observed on Venus, so the exoplanet’s glory is almost clear, but future observations with more powerful telescopes will reveal how closely the WASP-76 phenomenon compares to Venus. This may help determine if they are similar. Venus. If they match, this would be the first glories observed on an exoplanet.
If future research turns out a clear way to determine whether this is really Glory, these phenomena could be a sign of the composition of an exoplanet’s atmosphere, depending on the types of elements and molecules the light is reflecting. They may be able to give you more details. They may even abandon the presence of water, which could mean habitability. WASP-76b’s hypothetical glory has not been conclusively demonstrated, but it is a rainbow in the dark.
Astronomy and Astrophysics, 2024. DOI: 10.1051/0004-6361/202348270