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Measurement of stellar age from uranium decay
Nature
|February 24, 2001
Summary
Astronomers precisely dated the Galaxy
Area of Science:
- Astronomy and Astrophysics
- Cosmochronology
- Stellar Evolution
Background:
- The age of the oldest stars provides a minimum age for the Universe.
- Radioactive dating of stars uses abundance ratios of radioactive and stable isotopes.
- 232Th is a long-lived radioisotope used for dating, but 238U offers higher precision.
Purpose of the Study:
- To detect the spectral line of singly ionized uranium (238U) in a metal-poor star.
- To use 238U as a precise cosmochronometer for dating Galactic stars.
- To establish a more accurate lower limit for the age of the Universe.
Main Methods:
- Spectroscopic analysis of the metal-poor star CS31082-001.
- Detection of the uranium spectral line at 385.957 nm.
- Comparison of observed and predicted isotopic abundance ratios.
Main Results:
- Successfully measured the 385.957 nm spectral line of singly ionized uranium.
- Determined the uranium abundance in CS31082-001 as log(U/H) = -13.7 +/- 0.14 +/- 0.12.
- Estimated the age of the star to be 12.5 +/- 3 Gyr, providing a direct age for the Galaxy.
Conclusions:
- The detection of the 238U line in CS31082-001 marks a significant advancement in stellar dating.
- This cosmochronometer offers the most direct age determination for the Galaxy to date.
- Future improvements in theoretical and laboratory data will enhance the precision of age limits for the Universe.
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