Using data from ESA’s Characterising ExOplanet Satellite (CHEOPS) and several other ESA and NASA missions, astronomers have detected signs of the rainbow-like ‘glory effect’ in the atmosphere of the ultra-hot Jupiter WASP-76b. This effect occurs when light is reflected off clouds made up of a perfectly uniform but so far unknown substance. Seen often on Earth, the ‘glory effect’ has only been found once on another planet, Venus. If confirmed, this first extrasolar glory will reveal more about the nature of this puzzling exoplanet, with exciting lessons for how to better understand strange, distant worlds.
An artist’s impression of the rainbow-like ‘glory effect’ in the atmosphere of WASP-76b. Image credit: ESA.
WASP-76b is an ultra-hot Jupiter located 640 light-years away in the constellation of Pisces.
First discovered in 2016, this exoplanet orbits the F-type star WASP-76 once every 1.8 days.
WASP-76b is tidally-locked to its star; it takes as long to rotate around its axis as it does to go around the parent star.
On its day side, the planet receives thousands of times more radiation from its star than the Earth does from the Sun.
Its day side temperature climbs above 2,400 degrees Celsius (4,352 degrees Fahrenheit), high enough to vaporize metals. But the night side temperature is much lower — 1,316 degrees Celsius (2,400 degrees Fahrenheit).
Here, elements that would form rocks on Earth melt and evaporate, only to condense on the slightly cooler night side, creating iron clouds that drip molten iron rain.
But astronomers have been puzzled by an apparent asymmetry, or wonkiness, in WASP-76b’s ‘limbs’ — its outermost regions seen as it passes in front of its host star.
“WASP-76b is ‘inflated’ by the intense radiation from its star,” said Dr. Monika Lendl, an astronomer at the University of Geneva.
“So, although it is 10% less massive than our cousin Jupiter, it is almost twice as big.”
“What’s important to keep in mind is the incredible scale of what we’re witnessing,” said Dr. Matthew Standing, an astronomer at ESA.
“WASP-76b is several hundred light-years away — an intensely hot gas giant planet where it likely rains molten iron. Despite the chaos, it looks like we’ve detected the potential signs of a glory. It’s an incredibly faint signal.”
In the study, the authors analyzed data from different ESA and NASA missions including CHEOPS, TESS, Hubble and Spitzer.
CHEOPS intensively monitored WASP-76b as it passed in front of and around its Sun-like star. After 23 observations over three years, the data showed a surprising increase in the amount of light coming from the planet’s eastern ‘terminator’ — the boundary where night meets day.
This allowed the astronomers to disentangle and constrain the origin of the signal.
“This is the first time that such a sharp change has been detected in the brightness of an exoplanet, its ‘phase curve’,” said Dr. Olivier Demangeon, an astronomer at the Instituto de Astrofísica e Ciências do Espaço in Portugal.
“This discovery leads us to hypothesize that this unexpected glow could be caused by a strong, localized and anisotropic (directionally dependent) reflection — the glory effect.”
“Never before have we seen these colorful, concentric rings on an extrasolar body,” said Dr. Thomas Wilson, an astronomer at the University of Warwick.
“So this first exoplanetary glory, if confirmed with future studies, would make WASP-76b a truly unique body, and give us a beautiful tool for understanding the atmospheres of distance exoplanets and how habitable they could be.”
Confirmation of the glory effect would mean the presence of clouds made up of perfectly spherical droplets, that have lasted at least three years or are being constantly replenished.
For such clouds to persist, the temperature of the atmosphere would also need to be stable over time — a fascinating and detailed insight into what could be going on at WASP-76b.
Importantly, being able to detect such minute wonders so far away will teach scientists and engineers how to detect other hard-to-see but critical phenomena. For example, sunlight reflecting off liquid lakes and oceans — a requirement for habitability.
“Further proof is needed to say conclusively that this intriguing ‘extra light’ is a rare glory,” said Dr. Theresa Lüftinger, project scientist for ESA’s upcoming Ariel mission.
“Follow-up observations from the NIRSPEC instrument onboard the NASA/ESA/CSA James Webb Space Telescope could do just the job. Or ESA’s upcoming Ariel mission could prove its presence. We could even find more gloriously revealing colors shining from other exoplanets.”
A paper on the findings was published in the journal Astronomy & Astrophysics.
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O.D.S. Demangeon et al. 2024. Asymmetry in the atmosphere of the ultra-hot Jupiter WASP-76b. A&A 684, A27; doi: 10.1051/0004-6361/202348270
Source : Breaking Science News