Tiny Pebbles Gave Rise to One of the Galaxy’s Most Extreme Worlds

Tiny remnants from a young star’s birth—grains of rock and dust—played a key role in the formation of one of the most bizarre and extreme exoplanets we’ve ever discovered.

Meet Tylos: A Planet of Vaporized Metals

This planet, named Tylos (also known as WASP-121b), is no stranger to the spotlight. Located about 880 light-years away, it orbits so close to its host star that its skies are filled with vaporized metals—a true inferno of a world.

Now, new insights reveal that this fascinating gas giant, one of the most thoroughly observed in our galaxy, likely emerged from the swirling debris surrounding its star in the early stages of the system’s development.

The Smoking Gun: Vaporized Rock in the Atmosphere

What provided the evidence? Clouds of silicon monoxide—essentially vaporized rock. Using data from the James Webb Space Telescope (JWST), astronomers also identified water vapor, carbon monoxide, and methane in the planet’s atmosphere.

“The ratios of carbon, oxygen, and silicon help us trace the planet’s formation history and the materials that built it,” says Thomas Evans-Soma, an astronomer at the University of Newcastle in Australia and lead author of the new study.

A Superheated World on a Rapid Orbit

Tylos is about 1.75 times wider than Jupiter but only slightly more massive, orbiting its star, Dilmun, at an incredible pace—completing a full orbit in just 30 hours. The proximity to its star causes the planet’s atmosphere to balloon and gradually evaporate under the intense heat.

Because Tylos passes directly in front of its star from our point of view, it’s perfectly positioned for atmospheric analysis. When starlight filters through its inflated atmosphere, certain molecules absorb specific wavelengths, leaving behind detectable signatures that researchers can decode to determine the planet’s chemical composition.

Tylos belongs to a class of exoplanets called hot Jupiters—gas giants that orbit dangerously close to their stars. But how they got there remains a puzzle. These planets likely didn’t form so close, since the extreme radiation would prevent gas accumulation. The prevailing theory is that they formed farther out and then migrated inward.

The first-ever detection of silicon monoxide in an exoplanet atmosphere came in 2022. It’s a rare and challenging molecule to observe. In Tylos, however, the unique blend of atmospheric chemicals gave researchers the clues they needed to trace the planet’s origins.

The Birth of Planets: From Dust to Worlds

Stars form from dense clouds of gas and dust, with surrounding material flattening into a disk that feeds the young star. When the star becomes strong enough, its winds blow away remaining material. What’s left condenses into pebbles and ice grains, slowly forming planets.

Closer to the star, ice turns to gas—a boundary known as the snow line. Each type of ice vaporizes at a different distance, depending on the star’s heat.

By analyzing the molecular ratios in Tylos’ atmosphere, the researchers determined that the planet likely formed in a region where methane existed as a gas, but water remained frozen. In our own Solar System, that corresponds to the zone between Jupiter and Uranus. Given that Dilmun is hotter than the Sun, Tylos must have originated even farther out before spiraling inward.

This journey offers strong support for the idea that hot Jupiters migrate after forming in colder regions.

A New Mystery on the Nightside

However, the study raised a new mystery. Methane was found in Tylos’ nightside atmosphere—the side that always faces away from the star. Methane normally breaks down under high heat, and should not be present at detectable levels even after the gas circulates from the scorching dayside.

Yet, methane was found in high quantities, high up in the nightside atmosphere. This suggests a powerful process at work—likely vertical mixing, where deeper atmospheric layers rich in methane are pushed upward faster than expected.

“This discovery challenges existing models of exoplanet atmospheric dynamics,” says Evans-Soma. “Our findings suggest stronger vertical movement than we thought possible.”

Despite being one of the most intensely studied exoplanets among the nearly 6,000 discovered so far, Tylos continues to surprise—and deepen our understanding of how extreme planetary systems form and evolve throughout the Milky Way.

Read the original article on: Science Alert

Read more: The Most Intense Solar Storm in History Occurred 14,000 Years Ago