Discovery of traces of one of universe's oldest stars excites boffins

By James Maynard, Tech Times | August 23, 10:07 AM

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Supernova remnant

A star that lived soon after the formation of matter in the Universe could have formed another neighbor, just outside our own galaxy.
(Photo : NASA/DOE/Fermi LAT Collaboration, NOAO/AURA/NSF, JPL-Caltech/UCLA)

An ancient star, one of the oldest in the Universe, may have been recognized by astronomers. This stellar body, which disappeared long ago, may have possessed a mass up to 100 times greater than our own Sun. 

Massive stars live much shorter lives than their smaller brethren. Giant stars, like the one inferred by the Japanese astronomy team, end their lives in a massive supernova explosion, sending heavy elements into open space. These materials become the building blocks of planets and asteroids, and help fuel the birth of new stars.

This ancient star exploded long ago, but astronomers believe the blast assisted in the formation of another star, SDSS J001820.5-093939.2, near the site of the first body. This newer stellar body has an unusual chemical composition, poor in metals. A similar makeup was predicted by astrophysicists for stars whose births were triggered by supernovas of supermassive stars.

Astronomers at the Subaru Telescope in Hawaii examined this star, located in a stellar halo around the Milky Way galaxy. The research team searched for evidence of how the body formed. Because these early massive stars were so short-lived, examination of objects they have affected nearby is the only trace left of the ancient bodies.

"The impact of very-massive stars and their explosions on subsequent star formation and galaxy formation should be significant," Wako Aoki, from the National Astronomical Observatory of Japan, and lead author of an article announcing the discovery, said.

First-generation very massive stars were formed in the early Universe, and lived extremely short lives before exploding. These population III stars were created from the hydrogen and helium that made up nearly all the matter in the early Universe. After burning at extremely high temperatures during their short lifetime, they exploded, spewing the material which created additional stars.

Volker Bromm, astrophysicist at the University of Texas, believes the supermassive star likely exploded in a pair-instability supernova. This cause of interstellar death occurs when photons, units of light, obtain so much energy that they are converted to mass, in accordance with Einstein's famous equation. A loss of outward pressure, normally provided by the photons, as well as extra mass from the additional matter, causes the star to collapse on itself.

The star then burns all the remaining fuel -- it's a thermonuclear-powered supernova explosion --and this is so strong that it completely destroys the star. In this case, there would be no compact remnant - no neutron star, no black hole - left behind, Bromm told reporters.

Study of evidence for the ancient star and the chemical composition of this first-generation very massive star was profiled in the journal Science.

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