This giant planet formed in a strange way, scientists find
The distant world WASP-121b is so hot that it hosts metallic clouds and rains gems.
Astronomers discovered the gas giant planet — dubbed a "hot Jupiter" — in 2016, but have continued to investigate this intriguing exoplanet, which is a world beyond our solar system.
Using a powerful telescope equipped with an instrument (called a spectrometer) that can detect the composition of far-off objects, researchers found WASP-121b contains an unusual amount of rocky material, indicating the massive planet formed quite close to its star. If a world has a higher proportion of rocky material (like iron and silicon) compared to ices, this means it formed in a zone of the developing solar system, called a "protoplanetary disk," where it was too hot for many ices to form.
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But this observation contradicts what planetary scientists thought about how gaseous giants like WASP-121b spawned in their expansive, donut-shaped protoplanetary disk. The leading theory was these giant worlds were created in the outer part of these disks, where it's frigid, but there are copious amounts of gas available to amass onto a developing world.
"Our measurement means that perhaps this typical view needs to be reconsidered and our planet formation models revisited," Peter Smith, an astrophysicist at Arizona State University’s School Of Earth and Space Exploration and coauthor of the research, said in a statement. The research was recently published in The Astronomical Journal.
The graphic below shows how different materials solidify and vaporize based upon the proximity to their star. In the mid-region, beyond where everything vaporizes, rock materials solidify, but it's too hot for gases, like water vapor or CO2, to turn to ice.
The researchers used the powerful Gemini South telescope, located at 8,980 feet in the Chilean mountains, to peer into the atmosphere of distant WASP-121b, located some 880 light-years away in the Milky Way galaxy. Attached to the telescope was an instrument called the Immersion GRating INfrared Spectrometer, or IGRINS, which separates out the light observed from distant space objects, like a prism. The different light spectrums reveal the atmospheric composition of these distant worlds.
Peering into WASP-121b also revealed more about the intensity of this alien realm. "The climate of this planet is extreme, and nothing like that of Earth,” Smith explained.
"The climate of this planet is extreme, and nothing like that of Earth."
The planet is tidally locked to its star — like the moon is locked to Earth — meaning that one side of WASP-121b is incessantly seared by its star, while the other is dark and (relatively) cooler. On the dayside, elements like calcium are vaporized into the air. But on the nightside, these materials can condense and produce rain. The astronomers, for example, spotted "calcium rain" on WASP-121b.
There are no "hot Jupiters" like WASP-121b in our solar system. Nor are there any rocky super-Earth worlds. Yet exoplanet researchers have found both these planet types are common in our galaxy. Although there are some strange-sounding worlds out there, it may be that it's our cosmic neighborhood that's actually quite unusual. And not just that. Our solar system may host an extraordinarily rare galactic phenomena: an intelligent, communicating civilization.
Mark was the science editor at Mashable. After working as a ranger with the National Park Service, he started a reporting career after seeing the extraordinary value in educating people about the happenings on Earth, and beyond.
He's descended 2,500 feet into the ocean depths in search of the sixgill shark, ventured into the halls of top R&D laboratories, and interviewed some of the most fascinating scientists in the world.
