ASTRO3D: Anaemic Star Carries the Mark of Its Ancient Ancestor

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ASTRO3D: Anaemic Star Carries the Mark of Its Ancient Ancestor

Post by bystander » Thu Aug 08, 2019 6:30 pm

Anaemic Star Carries the Mark of Its Ancient Ancestor
ARC Centre of Excellence for All Sky Astrophysics in 3 Dimensions (ASTRO 3D) | 2019 Aug 01

Australian-led astronomers find the most iron-poor star in the galaxy, hinting at the nature of the first stars in the universe.

A newly discovered ancient star containing a record-low amount of iron carries evidence of a class of even older stars, long hypothesised but assumed to have vanished. ... Its diminutive iron content is enough to place the star – formally dubbed SMSS J160540.18–144323.1 – into the record books, but it is what that low level implies about its origin that has the astronomers really excited.

The very first stars in the Universe are thought to have consisted of only hydrogen and helium, along with traces of lithium. These elements were created in the immediate aftermath of the Big Bang, while all heavier elements have emerged from the heat and pressure of cataclysmic supernovae – titanic explosions of stars. Stars like the Sun that are rich in heavy element, therefore, contain material from many generations of stars exploding as supernovae.

As none of the first stars have yet been found, their properties remain hypothetical. They were long expected to have been incredibly massive, perhaps hundreds of times more massive than the Sun, and to have exploded in incredibly energetic supernovae known as hypernovae.

The confirmation of the anaemic SMSS J160540.18–144323.1, although itself not one of the first stars, adds a powerful bit of evidence. ...

Only a small amount of newly forged iron escaped the remnant's gravitational pull and went on, in concert with far larger amounts of lighter elements, to form a new star -- one of the very first second generation stars, that has now been discovered. ...

The Lowest Detected Stellar Fe Abundance: The Halo Star SMSS J160540.18-144323.1 ~ T. Nordlander et al
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