The planet’s upper atmosphere is around ten times hotter than any other globe yet recorded, which astronomers believe is driving heavy metals to escape the planet.

Key takeaways

  • WASP-121b’s upper atmosphere is about ten times hotter than any other planet measured, causing heavy metals to escape.
  • Using NASA’s Hubble Space Telescope, astronomers found that WASP-121b is so hot that it loses heavy metals like iron and magnesium, a first-time observation.
  • The planet, located 900 light-years from Earth, is puffed up and stretched due to its close orbit around a much hotter star, causing it to lose its outer layers.
  • This extreme heat allows not just lighter gases like hydrogen and helium, but also heavier metals to escape into space, which is unusual for hot Jupiters.
  • The findings support the theory that hot Jupiters lose mass over time, and upcoming telescopes like the James Webb Space Telescope will help identify more materials around these planets.
WASP-121b is so hot that the planet has puffed up beyond its ability to hold onto its own atmosphere, and is instead streaming it away as it flies around its star every 30 hours. NASA/ESA/J. Olmsted/STScI

Astronomers have used NASA’s Hubble Space Telescope to measure the temperature of an exoplanet named WASP-121b and discovered that the planet is so hot that heavy metals seep behind it as it orbits its core star. This is the first time scientists have observed such a behavior.

Since the beginning of the exoplanet era, when astronomers first discovered planets outside our solar system, these so-called hot Jupiters have commanded interest. They’re as massive as or larger than our planet Jupiter, made primarily of gaseous hydrogen and helium, and orbit frighteningly near to their star. These giant planets can circle in hours or days. And because of their clinginess, they may be heated to thousands of degrees.

However, WASP-121b is out of the ordinary for its class. The planet’s upper atmosphere is approximately ten times hotter than any other globe yet measured. Astronomers believe that high heat is driving the metals, as well as lighter things, to puff up and flow away from the planet.

“Heavy metals have been seen in other hot Jupiters before, but only in the lower atmosphere,” David Sing of Johns Hopkins University in Baltimore, Maryland, stated in a press statement. He is the lead author of a study published in the Astronomical Journal. “So you’re not sure if they’re escaping or not. WASP-121b detects magnesium and iron gas so far from the planet that they are not gravitationally bound.

Losing control

WASP-121b is approximately 900 light-years distant from Earth and circles a star significantly bigger and hotter than our Sun. In certain aspects, it resembles many other hot Jupiters. The extreme heat from its neighboring star has caused WASP-121b to puff out like a marshmallow. Because of its puffiness, it has less gravitational control over its outer layers, and the nearest star is more than willing to begin dragging that material away. As WASP-121b revolves, scientists can watch it stretching out into a football shape and shedding material as it around its star.

And the severe heat on WASP-121b is completely novel. That is what allows light gases like hydrogen and helium to escape, as well as heavy metals like iron and magnesium. Typically, these heavier components remain condensed in a planet’s lower atmosphere, even at high temperatures. However, WASP-121b’s 4,600 degrees Fahrenheit is sufficient to propel even heavy metals up into the atmosphere, where the planet looks to be losing them.

When astronomers began exploring WASP-121b with the Hubble Space Telescope, they already knew it was an extraordinarily hot planet. They observed the planet during transits, which occur when it passes in front of its star as viewed from Earth. Even at such high temperatures, the planet and its escaping gasses are too far away to view directly. However, scientists can watch the light they detect from the WASP-121 star and how it changes when the planet or its trailing gasses pass between the star and Earth. That thorough image is what led them to the identification of the metals also flowing out from the planet.

Astronomers believe hot Jupiters, such as WASP-121b, cannot originate thus close to their stars since such stars are frequently seen shedding material. Instead, they believe that planets like Jupiter developed securely distant from their stars and then moved in. They also assume that certain smaller planets in tight orbits are previous hot Jupiters that have shed their puffy outer layers, leaving just dense cores.

These observations appear to confirm that scientists are on the right track in terms of hot Jupiters shedding mass. As additional telescopes, such as the James Webb Space Telescope, become operational in the future years, scientists will be able to search for even more sorts of materials orbiting these harsh planets.

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