Far out cosmology: Milky Way ancient stars (Introduction)

by David Turell , Saturday, July 08, 2023, 17:52 (502 days ago) @ David Turell

From one billion years after the Big Bang:

https://www.sciencealert.com/stars-from-the-dawn-of-the-universe-found-hidden-in-the-he...

"Ancient stars born during the Cosmic Dawn have been identified in the center of the Milky Way.

"As part of a survey to uncover some of the oldest known stars in the Universe, scientists conducted a comprehensive search for these ancient, but elusive, stars, and found that the measures they spin around the galactic center are relatively sedate, in spite of the chaos around them.

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"We can tell how old a star is based on how much metal is in it. When the first stars in the Universe formed, they had to make themselves out of the elemental material available at the time – mostly hydrogen and helium. But the nuclear furnaces burning in their cores started fusing the atoms of hydrogen into heavier things, from helium all the way up to iron.

"Then, when they exploded in messy supernovae, they seeded these heavier elements throughout space, along with even heavier elements forged in energetic split-second supernova processes. Subsequent stars therefore started their lives with a greater proportion of heavier material. The younger a star is, the more metal it's likely to have.

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"Astronomers think that the oldest of the old stars should be hanging out in the galactic center, but because the region is predominantly rich in metal, and there's a lot of dust blocking our view, they tend to be harder to find.

"Anke and her colleagues embarked on a project called the Pristine Inner Galaxy Survey (PIGS) to try and find them. By analyzing the spectrum of light emanating from a certain star, astronomers can find wavelengths amplified or dampened by the presence of certain elements. They looked for an elemental signature consistent with stars that are very low in metals, and identified around 8,000 candidates.

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"They used data from the Gaia observatory, which is an ongoing project to map the three-dimensional positions and motions of the stars in the Milky Way. With this, the researchers were able to determine the galactic orbits of their old stars.

"Arentsen and her colleagues found that orbits of the ancient stars around the galactic center are relatively slow.

"In addition, the older stars have more chaotic orbits, but they still have an average orbit around the galactic center.

"Finally, the orbits of the stars are mostly contained entirely within the galactic center. Even those stars on elliptical orbits tend to stay mostly within the central region of the Milky Way.

"'It is exciting to think that we are seeing stars that formed in the earliest phases of the Milky Way, previously largely out of reach. These stars likely formed less than a billion years after the Big Bang, so are relics from the early Universe," Arentsen says.'

Comment: just as I see our planet as privileged, I view our galaxy the same way, and I see this finding as an example of God directing traffic to designing our galaxy to be perfect for us.