The Oldest Stars Help Tell us how big the Universe is

The workings of the Universe.
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fred8615
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The Oldest Stars Help Tell us how big the Universe is

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Astronomers are struggling to understand the discrepancies when measuring the expansion rate of the universe with different methods, and are desperate for any creative idea to break the tension. A new method involving some of the oldest stars in the universe could just do the trick.

Astronomers have different methods for measuring the present-day expansion rate of the universe, known as the Hubble constant. One common method is to measure the brightness of distant supernovae. Another method is to examine the leftover light from the early universe, known as the cosmic microwave background. However, these two measurements disagree.

“One of the most exciting questions in cosmology today is whether there is new physics that is missing from our current understanding of how the universe is evolving. A current discrepancy in the measurement of the Hubble constant could be signaling a new physical property of the universe or, more mundanely, unrecognized measurement uncertainties,” said Wendy L. Freedman, the John and Marion Sullivan University Professor of Astronomy and Astrophysics.

Enter J-region Asymptotic Giant Branch (JAGB) stars, which are a particular kind of red giant with a lot of carbon in their atmospheres.

How do JAGB stars help? They appear to have a near-standard brightness, meaning that we can compare the brightness that we measure to the brightness that we know they have to calculate the distance to them. By combining that measurement with the recession speed of their host galaxies, we can estimate the expansion rate of the universe in a way independent of both supernovae and the cosmic microwave background.

Read more: https://www.universetoday.com/150453/th ... iverse-is/
Frederick J. Barnett
"Someone's got to take the responsibility if the job's going to get done!! Do you think that's easy?!" Gregory Peck - The Guns Of Navarone
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