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\t\t\t\t\t\t05\/04\/2024<\/span> For the first time, potential signs of the rainbow-like \u2018glory effect\u2019 have been detected on a planet outside our Solar System. Glory are colourful concentric rings of light that occur only under peculiar conditions.<\/p>\n Data from ESA\u2019s sensitive Characterising ExOplanet Satellite, Cheops, along with several other ESA and NASA missions, suggest this delicate phenomenon is beaming straight at Earth from the hellish atmosphere of ultra-hot gas giant WASP-76b, 637 light-years away.<\/p>\n Seen often on Earth, the 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.\u00a0<\/p>\n<\/p><\/div>\n<\/p><\/div>\n Data from Cheops and its friends suggest that between the unbearable heat and light of exoplanet WASP-76b\u2019s sunlit face, and the endless night of its dark side, may be the first extrasolar \u2018glory\u2019. The effect, similar to a rainbow, occurs when light is reflected off clouds made up of a perfectly uniform but so far unknown substance.\u00a0<\/p>\n<\/p><\/div>\n \u201cThere’s a reason no glory has been seen before outside our Solar System \u2013 it requires very peculiar conditions,\u201d explains Olivier Demangeon, astronomer at the\u00a0Instituto de Astrof\u00edsica e Ci\u00eancias do Espa\u00e7o (Institute of Astrophysics and Space Sciences) in Portugal and lead author of the study.<\/p>\n \u201cFirst, you need atmospheric particles that are close-to-perfectly spherical, completely uniform and stable enough to be observed over a long time. The planet’s nearby star needs to shine directly at it, with the observer \u2013 here Cheops \u2013 at just the right orientation.\u201d<\/p>\n<\/p><\/div>\n If confirmed, this first exoplanetary glory would provide a beautiful tool to understand more about the planet and star that formed it.<\/p>\n \u201cWhat\u2019s important to keep in mind is the incredible scale of what we\u2019re witnessing,\u201d explains Matthew Standing, an ESA Research Fellow studying exoplanets.<\/p>\n \u201cWASP-76b is several hundred light-years away \u2013 an intensely hot gas giant planet where it likely rains molten iron. Despite the chaos, it looks like we\u2019ve detected the potential signs of a glory. It\u2019s an incredibly faint signal.\u201d<\/p>\n This result demonstrates the power of ESA’s Cheops mission to detect subtle, never-seen-before phenomena on faraway worlds.<\/p>\n<\/p><\/div>\n WASP-76b is an ultra-hot Jupiter-like planet. While it is 10% less massive than our striped cousin, it is almost double its size. Tightly orbiting its host star twelve times closer than scorched Mercury orbits our Sun, the exoplanet is \u2018puffed up\u2019 by intense radiation.<\/p>\n<\/p><\/div>\n Since its discovery in 2013, WASP-76b has come under intense scrutiny and a bizarrely hellish picture has emerged. One side of the planet always faces the Sun, reaching temperatures of 2400 degrees Celsius. 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.<\/p>\n But scientists have been puzzled by an apparent asymmetry, or wonkiness, in WASP-76b\u2019s \u2018limbs\u2019 \u2013 its outermost regions seen as it passes in front of its host star.<\/p>\n Data from different ESA and NASA missions including TESS, Hubble and Spitzer, were also analysed in this revealing study, but it was when ESA\u2019s Cheops and NASA\u2019s TESS worked together that hints of the glory phenomenon began to appear.<\/p>\n 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\u2019s eastern \u2018terminator\u2019 \u2013 the boundary where night meets day. This allowed scientists to disentangle and constrain the origin of the signal.<\/p>\n \u201cThis is the first time that such a sharp change has been detected in the brightness of an exoplanet, its \u2018phase curve\u2019,\u201d explains Olivier.<\/p>\n \u201cThis discovery leads us to hypothesise that this unexpected glow could be caused by a strong, localised and anisotropic (directionally dependent) reflection \u2013 the glory effect.\u201d<\/p>\n<\/p><\/div>\n While the glory effect creates rainbow-like patterns, the two aren\u2019t the same. Rainbows form as sunlight passes through one medium with a certain density to a medium with a different density \u2013 for example from air to water \u2013 which causes its path to bend (refract). Different wavelengths are bent by different amounts, causing white light to split into its various colours and creating the familiar round arc of a rainbow.<\/p>\n<\/p><\/div>\n Glory, however, are formed when light passes between<\/i> a narrow opening, for example between water droplets in clouds or fog. Again, light\u2019s path is bent (in this case diffracted), most often creating concentric rings of colour, with interference between light waves creating patterns of bright and dark rings.<\/p>\n<\/p><\/div>\n 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 \u2013 a fascinating and detailed insight into what could be going on at WASP-76b.<\/p>\n 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 \u2013 a requirement for habitability.<\/p>\n<\/p><\/div>\n \u201cFurther proof is needed to say conclusively that this intriguing \u2018extra light\u2019 is a rare glory,\u201d explains Theresa L\u00fcftinger, Project Scientist for ESA\u2019s upcoming Ariel mission.<\/p>\n \u201cFollow-up observations from the NIRSPEC instrument onboard the NASA\/ESA\/CSA James Webb Space Telescope could do just the job. Or ESA\u2019s upcoming Ariel mission could prove its presence. We could even find more gloriously revealing colours shining from other exoplanets.\u201d<\/p>\n Olivier concludes: \u201cI was involved in the first detection of asymmetrical light coming from this weird planet \u2013 and ever since I have been so curious about the cause. It has taken some time to get here, with moments where I asked myself \u2013 \u2018Why are you insisting on this? It might be better to do something else with your time.\u2019 But when this feature appeared out of the data, it was such a special feeling \u2013 a particular satisfaction that doesn\u2019t happen every day.\u201d<\/p>\n \u00a0<\/p>\n Notes for editors<\/b><\/p>\n ‘Asymmetry in the upper atmosphere of the ultra-hot Jupiter WASP-76 b’ by O.D.S. Demangeon et al. is published in Astronomy & Astrophysics <\/i>on 5 April 2024. DOI: <\/p>\n<\/p><\/div>\n
\n\t\t\t\t300<\/span> views<\/small><\/span>
\n\t\t\t\t\t\t\t\t\t\t5<\/span> likes<\/small><\/span><\/p>\n<\/header>\nIn brief<\/h2>\n
In-depth<\/h2>\n<\/div>\n
\n\t\t\t\t\t\t\t\t<\/figcaption><\/figure>\n<\/p><\/div>\n
\n\t\t\t\t\t\t\t\t<\/figcaption><\/figure>\nA hellish planet with lopsided limbs<\/h2>\n
\n\t\t\t\t\t\t\t\t<\/figcaption><\/figure>\nBasking in WASP-76b\u2019s reflected glory<\/h2>\n
\n\t\t\t\t\t\t\t\t<\/figcaption><\/figure>\nWhat the first far-flung glory would mean<\/h2>\n
Glorious proof on the horizon<\/h2>\n