How do we know how old the Milky Way is?

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#milkyway #science #astrophysics

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REFERENCES (NO PAYWALL)
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Xiang & Rix (2022; most recent age determination of the Milky Way with GAIA sub-giants) - https://arxiv.org/pdf/2203.12110.pdf
Belokurov et al. (2018; GAIA sausage discovery) - https://arxiv.org/pdf/1802.03414.pdf
Myeong et al. (2018; GAIA sausage globular clusters) - https://arxiv.org/pdf/1805.00453.pdf
Gregg et al. (2004; HST stellar spectral library) - https://ntrs.nasa.gov/api/citations/2...
Skumanich (1972; gyrochronology correlation) - https://articles.adsabs.harvard.edu/p...
Bond et al. (2013; first estimate of age for HD140283 over age of the Universe) - https://arxiv.org/pdf/1302.3180.pdf
Tang & Joyce (2021; revised estimate of age of HD140283 less than age of the Universe) - https://arxiv.org/pdf/2105.11311.pdf

My previous video on how we know the Milky Way is spiral shaped -    • How do we know the Milky Way is a spi...  
My previous video on HD140283, the "Methuselah star" -    • Is the "Methuselah" star older than t...  

00:00 - Introduction
00:58 - The GAIA telescope surveying 1 billion stars
01:28 - Parallax & proper motion
02:23 - What the spectrum of a star tell us
03:46 - GAIA 3D map of the Milky Way
04:23 - How we know how long stars live (the Hertzpsrung Russel diagram)
06:12 - Stars formed earlier are made of different ratio of elements
07:07 - Fitting model spectra to get ages
07:47 - Other methods: GYROCHRONOLOGY
08:36 - Other methods: PHOTOMETRY
09:17 - The oldest star known and its uncertain age estimate HD140283 (no it's not older than the Universe)
10:03 - Let's do this with a big sample of sub-giant stars (Xiang & Rix 2022)
12:14 - Deriving the age of the Milky Way (Xiang & Rix 2022)
12:52 - Brilliant
13:26 - Bloopers


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👩🏽‍💻 I'm Dr. Becky Smethurst, an astrophysicist at the University of Oxford (Christ Church). I love making videos about science with an unnatural level of enthusiasm. I like to focus on how we know things, not just what we know. And especially, the things we still don't know. If you've ever wondered about something in space and couldn't find an answer online - you can ask me! My day job is to do research into how supermassive black holes can affect the galaxies that they live in. In particular, I look at whether the energy output from the disk of material orbiting around a growing supermassive black hole can stop a galaxy from forming stars.


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