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Astronomers have detected a rainbow-like phenomenon occurring on a planet outside our solar system for the first time, and it could reveal new information about alien worlds.
Observations by the European Space Agency’s Cheops space telescope, or Characterizing ExOplanet Satellite, have detected a “splendor effect” on WASP-76b, an ultra-hot exoplanet 637 light-years from Earth.
This effect, seen mostly on Earth, consists of concentric, colored rings of light and occurs when light is reflected from clouds of uniform matter.
Beyond Earth, the magnificence effect had only been seen on Venus until Cheops and other missions picked up an incredibly weak signal suggesting it was occurring in the atmosphere of hellishly hot WASP-76b. Based on the signal detected by Cheops, astronomers believe that the atmospheric event was pointing directly at Earth.
The researchers reported details of the observation April 5 in the journal Astronomy & Astrophysics.
“There’s a reason why no magnificence has ever been seen outside our Solar System; it requires very special conditions,” lead study author Olivier Demangeon, an astronomer at the Institute of Astrophysics and Space Sciences in Portugal, said in a statement. “First, you need atmospheric particles that are nearly perfectly spherical, completely uniform, and stable enough to be observed for long periods of time. “The planet’s nearby star needs to shine directly at it, with the observer (here Cheops) in just the right orientation.”
A wild, scorching planet
WASP-76b has intrigued astronomers since its discovery in 2013.
The exoplanet orbits close to its host star and receives intense heat and radiation. Radiation from this sun-like star (4,000 times the amount of radiation Earth receives from our sun) caused WASP-76b to swell, becoming nearly twice the size of Jupiter, the largest planet in our solar system.
The planet is tidally locked to its star; This means that one side of it, known as the day side, is always facing the star, while the other side is always at night.
The dayside of WASP-76B reaches scorching temperatures of 4,352 degrees Fahrenheit (2,400 degrees Celsius). Typically, the elements that make up rocks on Earth melt and evaporate during the day, then condense and form clouds that release a rain of molten iron at night.
Astronomers decided to focus on multiple observatories, including Cheops, the Hubble Space Telescope, the now-retired Spitzer Space Telescope, and NASA’s planet-hunting TESS mission, to study what appeared to be the light imbalance that occurred while WASP-76b was in orbit. in front of the home star.
Combined data from Cheops and TESS, or the Transiting Exoplanet Survey Satellite, hinted that the anomaly could be caused by an intriguing event occurring in the atmosphere above the dayside.
Cheops collected data from WASP-76b as the planet passed in front of its star, making 23 observations over three years.
When astronomers looked at the data, they noticed an unusual increase in light from the planet’s eastern “terminator,” the boundary light between the day and night sides. Meanwhile, less light emerged from the western terminator.
“This is the first time such a sharp change in the brightness, or ‘phase curve,’ of an exoplanet has been detected,” Demangeon said. “This discovery leads us to hypothesize that this unexpected glow may be due to a strong, localized and anisotropic (directionally dependent) reflection, namely the victory effect.”
Demangeon said he was excited to be involved in the first detection of this type of light from an exoplanet.
“It was a very special feeling, a special satisfaction that you don’t experience every day,” he said.
Colorful light to alien worlds
Victory and rainbows are not the same thing. A rainbow is formed when light bends as it passes successively through two media of different densities, such as air to water. As the light bends, it separates into different colors, creating a curved rainbow.
But the magnificence effect is created when light passes through a narrow aperture and bends to form colorful, patterned rings.
If astronomers do indeed see the spectacular impact on WASP-76b, it would mean that the planet has persistent clouds of perfectly spherical droplets, or constantly replenishing clouds. In both cases, the presence of such clouds indicates that the planet’s atmosphere has a constant temperature.
What exactly the clouds on WASP-76b are remains a mystery, but it may be iron, as the element has been detected in clouds on the planet before.
“The important thing to keep in mind is the incredible scale of what we are witnessing,” Matthew Standing, a European Space Agency research scientist who studies exoplanets, said in a statement. Standing was not included in the study.
“WASP-76b is a few hundred light-years away; it’s a dense hot gas giant planet that probably rains molten iron,” Standing said. “Despite the chaos, (researchers) appear to have identified potential signs of a victory. “This is an incredibly weak signal.”
According to the researchers, if astronomers can observe the faint signal of a phenomenon such as magnificence from hundreds of light-years away, it may be possible in the future to detect the presence of sunlight reflected from extraterrestrial bodies of water.
“More evidence is needed to say with certainty that this intriguing ‘extra light’ is a rare triumph,” Theresa Lueftinger, project scientist for the European Space Agency’s Ariel mission, said in a statement. He did not participate in the research.
The Ariel, or atmospheric remote-sensing infrared exoplanet major survey, is expected to launch in 2029 to study the atmospheres of a large and diverse selection of exoplanets.
Lueftinger said he believes the James Webb Space Telescope, or Ariel, could help prove the existence of the magnificence effect on WASP-76b.
“We may even find more spectacular colors shining from other exoplanets,” he said.
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