The history of the Universe contains some marvelous stories. Astronomers are in a way sky archeologists. Pointing powerful telescopes at the skies provides not only images of what happens somewhere, but what happened way back in time as well. Light travels fast, but the Universe is so large that if we capture images from afar, we are actually looking at the primordial times.
Dr. Wako Aoki from the National Observatory of Japan conducted a study on ancient star traces in the Universe. She and her colleagues released the results of studying a particular ancient star in the journal Science, under the title “A chemical signature of first-generation very massive stars.”
The star SDSS J0018-0939 died a long time ago by turning into a supernova. But researchers can still capture and analyze light from that particular explosion. The star was about 200 times larger than our Sun. Moreover, the level of iron contained by this star was 1000 less than that of the Sun.
The Universe was rather boring in the beginning. Things changed after the giant stars appeared. Although they had a very short lifespan, of only 3 million years, their size influenced the processes and produced violent deaths. Out of the resulting stellar dust, a second generation of stars was born, this time with a more complex chemical composition.
Astronomers regularly provide us with deeper understanding of how the Universe works. Recently, scientists discovered that dwarf galaxies ‘dance’ around larger galaxies.
Ancient star traces hint at the huge sizes of the first stars
“Our discovery provides the very first evidence, or signature, for the existence of such very massive stars,” Aoki said. “And very massive stars have a very large impact on star formation, galaxy formation in the early universe, so their existence is very essential in studying the early universe.”
Astronomers decipher the composition of celestial bodies by analyzing the wavelengths. When a color is present or missing, it tells if a certain chemical is present.
Because earlier stars had a less complex chemical composition, they reached enormous sizes. When a star increases its chemical complexity, it cannot go over a certain size. Because of that, stars 100 times larger than our Sun are very rare now. Not a single one was discovered in our galaxy.
SDSS J0018-0939 suffered an extremely violent ending called Pair-Instability supernova, meaning there were no physical traces after the event. Everything scattered around, enriching the vicinities with metals. The next generation of telescopes, including Nasa’s James Webb Space Telescope, will help scientists shed more light on these ancient star traces.