Korean researchers identify key step in planet formation

South Korean researchers have identified a long elusive mechanism underlying the formation of planets in the solar system. The team has, for the first time, directly observed the migration pathway of crystalline silicates, materials found in rocky planets and in comets that exist far from stars like the sun.

The Ministry of Science and ICT said on Jan. 21 that Professor Lee Jeong-eun of Seoul National University’s Department of Physics and Astronomy successfully observed the process through which silicates crystallize during star formation. The findings were published in the Jan. 22 issue of the international scientific journal Nature.

The crystallization of silicates in the solar system offers crucial clues to the formation of terrestrial planets. About 90 percent of Earth’s crust consists of silicates, whose crystalline structure can form only at temperatures exceeding 600 degrees Celsius. Yet crystalline silicates have also been found in comets located in the cold outer reaches of the solar system, raising longstanding questions about how materials created in extreme heat could have traveled so far from the sun.

Lee, who has studied star formation for more than two decades, suspected that the explanation lies in events occurring at the earliest stage of a star’s life, known as the protostellar phase. During this stage, a protostar grows by drawing in material from a surrounding disk of dust and fine particles. While this process was once thought to proceed at a steady pace, recent studies have shown that protostars experience intermittent bursts of rapid accretion, marked by sudden surges in mass intake. Lee hypothesized that these episodic accretion events are the key reason comets in the outer solar system contain crystalline silicates.

To test the hypothesis through direct observation, the research team secured observation time on the James Webb Space Telescope operated by NASA, a distinction granted to only one research group in South Korea. The team focused on a protostar known as EC 53 in the Serpens Nebula, which was considered an ideal target because its brightness varies on an approximately 18-month cycle, signaling a regular alternation between burst and quiescent phases.

Observations using the James Webb Space Telescope confirmed that spectral signatures of crystalline minerals appeared only during burst phases. This finding indicates that crystalline silicates form in the hot inner regions of the disk close to the protostar during periods of rapid accretion. The team also found that once formed, these crystalline silicates can be carried from the inner disk to the cold outer regions by outward-blowing disk winds.

Lee said the study demonstrates how decades of accumulated research experience can culminate in a scientific breakthrough. She added that the team plans to conduct further observations to determine whether silicate crystallization and material transport processes occur universally, and how they vary across different stages of stellar evolution.


최지원 기자 jwchoi@donga.com