A notoriously harsh planet may have just unveiled one of the most breathtaking sights previously thought to be exclusive to Earth’s atmosphere.
In the skies of WASP-76b, laden with metals, astronomers believe they’ve glimpsed a radiant, multicolored aura known as a glory, a marvel unseen outside our Solar System, and observed only on Earth and Venus within it.
Characterized by concentric circles surrounding a luminous core, this stunning optical effect arises under particular conditions, namely when light encounters a cloud of uniformly sized spherical droplets.
The presence of a glory on WASP-76b hints at the enigmatic nature of this distant world’s atmosphere.
“Seeing a glory beyond our Solar System is unprecedented because it demands quite specific circumstances,” states Olivier Demangeon, an astronomer with the Institute of Astrophysics and Space Sciences in Portugal.
He explains, “You need atmospheric particles that are almost perfectly round, uniformly sized, and stable enough for observation over extended periods. Additionally, the planet’s star must illuminate it directly, with the observer – in this case, Cheops – positioned precisely.”
WASP-76b fascinates planetary scientists with its close orbit around a star slightly larger than the Sun in the Pisces constellation, 640 light-years away. Its proximity to its star results in scorching dayside temperatures capable of vaporizing iron, which indeed forms clouds in its expansive atmosphere. This exoplanet, roughly the mass of Jupiter but 185 percent its size, showcases a varied atmospheric composition, including sodium, calcium, and iron, among other elements, making it one of the most studied planets in the galaxy.
A peculiar brightness variation at the planet’s day-night boundary, noted in data from the European Space Agency’s Cheops satellite, suggests a potential glory effect, according to Olivier. This phenomenon, though faint and requiring further verification, could unveil new aspects of WASP-76b’s atmospheric composition.
The consistency of this effect over 23 observations spanning three years suggests the persistent presence of spherical aerosol droplets in the planet’s clouds, implying stable atmospheric temperatures over time.
Should this indeed be a glory, modeling the planet’s atmospheric conditions will be necessary to understand the underlying mechanics. Moreover, confirming a glory on WASP-76b could provide a methodological template for identifying similar phenomena on other exoplanets, potentially revealing features like starlight reflecting off liquid surfaces, akin to sunlight dancing on Earth’s oceans.
