Korean researchers uncover how planets, comets form away from stars

Korean researchers have uncovered the secret to how planets and comets could form far from a star — considered a mystery until now — by finding the key in a substance named crystalline silicates as the building blocks.

Serpens Nebula [NASA/ESA/CSA/STSCL]

Korean researchers have uncovered the secret to how planets and comets could form far from a star — considered a mystery until now — by finding the key in a substance named crystalline silicates as the building blocks.

A team led by Lee Jeong-eun, a professor in the Department of Physics and Astronomy at Seoul National University, has identified the mechanism by which crystalline silicates form and move in the course of star formation. The team directly observed the process using the James Webb Space Telescope (JWST), the most powerful space telescope currently in operation, and its findings were published Wednesday in the journal Nature.

Crystalline silicates are silicate minerals with a regular crystal structure. Silicate materials account for about 90 percent of the material on Earth and are a core component of terrestrial planets and comets.

Silicates originally exist as amorphous dust surrounding young stars. For this amorphous silicate dust to transform into a crystalline form with an orderly atomic structure, it must be heated to temperatures above 600 degrees Celsius (1,112 degrees Fahrenheit).

However, crystalline silicates — which can only form under such high-temperature conditions — have also been found in comets that formed in the extremely cold outer regions of the solar system. How this material was created and then transported to those frigid outskirts has remained a long-standing puzzle in astronomy.

Seoul National University professor Lee Jeong-eun gives a presentation at the government complex in Sejong on Jan. 19, about her team's research on how silicates crystallize during planet formation. [YONHAP]

Lee’s team selected as its target the object EC 53, a protostar located in a nebula in the constellation Serpens. A protostar is a very young star in an early formation stage that rapidly accretes surrounding material. EC 53 is unusual in that it undergoes regular cycles of outbursts and quiescent phases roughly every 18 months.

The researchers found that crystalline silicates are not present in the star from the beginning but are newly created during its outburst phase. In a protoplanetary system such as the early solar system, gas and dust clouds orbit the central newborn star in a flattened structure known as a disk. The team confirmed that crystalline silicates formed freshly within this disk during EC 53's outburst.

They also found that these particles are expelled outward, carried along by flows of gas and dust that make up the disk. High-resolution JWST observations showed that the outflow is fast near the center and slows toward the outer regions. In other words, winds generated inside the disk during an outburst can physically transport the newly crystallized particles all the way out to the cold, distant regions where comets form — a process the team was able to observe directly.

“The solar system went through the same formation process, and our results provide an important clue for explaining how planetary systems — including the solar system and exoplanetary systems — are formed,” Lee said. “Going forward, we plan to use the Spherex space telescope to find other erupting protostars and determine whether the crystallization of silicates is a universal phenomenon in star and planet formation.”

This article was originally written in Korean and translated by a bilingual reporter with the help of generative AI tools. It was then edited by a native English-speaking editor. All AI-assisted translations are reviewed and refined by our newsroom. BY KIM MIN-JEONG [kim.minyoung5@joongang.co.kr]