About Kyung Hee

Home > About Kyung Hee > Media & Press > News



NO.332 07.28.2017

On Wide Binaries of Very Low-Mass Stars: Secrets of Their Origin

Professor Jeong-Eun Lee at the Department of Astronomy & Space Sciences and her team have unfolded the formative mechanism of wide binaries of very low-mass stars for the first time in the world


Using the largest interferometer radio telescope in the world, ALMA (Atacama Large Millimeter/submillimeter Array), the team observed that each component of a wide binary system with very low-mass in a very early stage of formation has a circumstellar disc and that the rotational axes of the discs are misaligned, meaning they were not formed out of a single disc fragmentation.

The misaligned rotational axes show that the wide binary system of very low-mass stars was formed out of a turbulent fragmentation of molecular core, namely, through the same formative mechanism as ordinary binary systems. The findings were published on June 30, 2017, in Nature Astronomy.

Observation of very low-mass wide binary system with ALMA
The formative mechanism of binary systems has been speculated with several theories, but the case of very low-mass binaries has not been largely understood, as they are very dim and difficult to observe. Professor Lee’s team chose a wide very low-mass protostellar binary in Taurus called IRAS 04191+1523 and observed the system with ALMA.


The distance between the two members of the binary system is about 860 AU, meaning it is 860 times the distance between Earth and the Sun, which is known as one astronomical unit (AU). The team determined that the age of the stars was younger than 500,000 years, which is extremely young in space time, and thus suitable to be the subject of their study to figure out how the stars were formed. ALMA, the largest interferometer in the world, combines 66 antennae, each with a diameter of 12 meters, to electronically form single gigantic radio telescope operating in millimeter and submillimeter wavelengths.


When the team analyzed the radio spectrum of carbon monoxide molecules (C18O) from the binary, they confirmed that the mass of the stars was very low (about 10% the mass of the Sun) and that the circumstellar discs of the two stars were not on the same plane, namely, the rotational axes of the discs were not aligned. Professor Lee said, “Our observation confirmed that the two stars in the binary were not formed out of a single disc fragmentation but created through a turbulent fragmentation of molecule core.”


“Theoretical cornerstone for understanding low-mass stars and how they were formed”
Professor Lee said, “The formative mechanism of very low-mass binaries has been a controversial subject, but our research has confirmed that these were made in the same way with ordinary binary systems. This will be a great point of departure to better understand the formation process of very low-mass stars and brown dwarfs, leading to a complete theory of formation for very low-mass stars.”


Professor Jeong-Eun Lee (first and correspondence author) led this research with the participation by Dr. Seokho Lee of State University of New York at Fredonia, Minho Choi of Korea Astronomy and Space Science Institute, and others, with the funding provided by National Research Foundation of Korea and Korea Astronomy and Space Science Institute.

Facebook 0
Twitter 0

Return to News

News List

Highlight News