Older Stars, New Age for the Universe

The oldest stars appear to be about a billion years older than astronomers had estimated.

The universe has been around for an extra long time.

Astronomers used to estimate that the oldest stars were about 13 billion years old. New data suggest that these stars are nearly a billion years older than that.

Measurements at an Italian underground particle accelerator, called Luna, provided a new birth date for the universe.

© Matthias Junker LNGS-INFN

For most of its life, a star produces energy and heat by fusing hydrogen to make helium inside its core. Near the end of its life, when its hydrogen supply is running low, the star continues to convert hydrogen into helium but requires the presence of carbon, nitrogen, and oxygen to do so.

Two teams of scientists have now used particle accelerators—atom smashers—to mimic the conditions inside stars. By studying high-energy collisions between hydrogen nuclei (protons) and nitrogen nuclei, the researchers could check how quickly nuclear reactions inside a star proceed.

Both groups, one at the University of North Carolina at Chapel Hill and the other at the National Institute for Nuclear Physics in Italy, found that the reactions occur only half as fast as had been estimated.

Such a slow reaction time allows gravity to shrink a star more than it would if the reaction were faster. As a result, an elderly star looks brighter than it otherwise would. Brightness is supposed to indicate how old a star is.

Now that they know how deceptive brightness can be, astronomers have had to revise their estimates of star age.

In line with observations from a satellite called the Wilkinson Microwave Anisotropy Probe, the universe now appears to be about 13.7 billion years old, astronomers say. That’s quite a lot of time to ponder.—E. Sohn

Going Deeper:

Cowen, Ron. 2004. Old stars even older: Determining a new age for the universe. Science News 165(May 22):323. Available at http://www.sciencenews.org/articles/20040522/fob1.asp .

You can learn more about stars, galaxies, and the age of the universe at imagine.gsfc.nasa.gov/docs/science/mysteries_l1/age.html and starchild.gsfc.nasa.gov/docs/StarChild/universe_level1/universe.html (NASA Goddard Space Flight Center).

Find out more about the Wilkinson Microwave Anisotropy Probe at map.gsfc.nasa.gov/ (NASA Goddard Space Flight Center).

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