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NMSU Researcher Part Of Team That Discovered Star

  New Mexico State University researcher Young Sun Lee is among a group of collaborators that has discovered a star that may have formed just after the very first generation of stars in the universe. The research is documented in “A chemical signature of first-generation very massive stars,” an article published in the Aug. 22 issue of the prestigious publication, “Science” magazine.

The international team of researchers discovered a metal-poor, low-mass star, dubbed SDSS J0018-0939, which has chemical abundance ratios linked to nucleosynthesis of first-generation stars.

First generation stars, which formed about 100 million years after the Big Bang, are estimated to have formed with masses more than a hundred times the sun.

SDSS J0018-0939 was first identified by a project undertaken as part of the Sloan Digital Sky Survey, which uses a 2.5m telescope in the Sacramento Mountains of southern New Mexico at the Apache Point Observatory that is operated by New Mexico State University.

The star’s peculiar chemical abundance pattern was revealed by an analysis of a high-resolution spectrum obtained by Subaru 8-meter telescope in Hawaii. This pattern matches what is expected to be synthesized in the very first generation of stars in the universe. These stars exploded in gigantic supernova explosions, enriching the gas from which the next generation of stars formed.

The article explains that the abundance ratios of the star are a result of an explosion of a very massive first-generation star and the elements formed by the first generation of massive stars polluted the gas that formed the next generation of stars. Stars with masses slightly less than the sun have very long lifetimes, long enough to still be shining, Lee explained, and SDSS J0018-0939 is one of them.

In addition to Lee, collaborators include Wako Aoki of the National Astronomical Observatory of Japan, Nozomu Tominaga of Konan University, Timothy C. Beers of the University of Notre Dame and Satoshi Hondo of the University of Hyogo.

Discovery of SDSS J0018-0939 could help understand the evolution of the first generation of stars and their nucleosynthesis that occurred during their explosions.

Lee, who grew up in South Korea, completed his doctorate at Michigan State University where he also spent several years in a postdoctoral position. He spent the last two years as a Tombaugh Scholar at NMSU.

“In high school I was fascinated by the solar system and the universe, in that how it works and how large it is. It is like a world beyond our imagination” he said. “I lived in the countryside and at night I’d look up at the sky and see a lot of twinkling bright stars and beautiful constellations. Who wasn’t captivated by the sea of the universe? That was motivation for me to be an astronomer.”

The Tombaugh Scholars program was started in 1986 to honor NMSU astronomy professor Clyde Tombaugh, who discovered Pluto in 1930. Initially funded through a grassroots effort – small private donations – the endowment now sits at $1.4 million.

“The program funds research for postdoc researchers who are at just the beginning of their astronomical career,” said Bernie McNamara, director of the Tombaugh Scholars program. “It allows them to come and be supported, to help get that important foothold that they need to jumpstart their career. It also allows NMSU to bring in top, world-class talent to our institution.

“Clyde would be extremely happy with the progress the program has made. When he and his wife were engaged in a two-year international speaking campaign, he donated every penny of that to the endowment.”

Lee is the fifth scholar to receive funding through the program. He is now back in South Korea and has been hired as a tenure track faculty member at Chungnam National University in Daejeon, where he will continue his research. 

Information from NMSU