Finding the age of a galaxy

A key to generating the new number was knowledge that the earliest stars formed almost entirely from hydrogen. They lived short lives and exploded violently, spewing new and heavier elements into their surroundings.

The new age estimate is based on measurements of the element beryllium in two stars within a globular cluster of stars called NGC 6397. The amount of Beryllium, one of the lightest elements, increased with time and serves as a sort of “cosmic clock,” according to the team, led by Luca Pasquini of the European Southern Observatory.

The stars were found to be roughly 13.4 billion years old. The researchers added to that an interval of about 200 million years they say it took for previous generations of stars in the Milky Way to form, explode, and seed the fledgling galaxy with the goods necessary to forge the types of stars found in NGC 6397.

Radioactive dating of the elements Thorium 232 and Uranium 238 in one star put the galaxy at 14 billion years old, plus or minus 2.4 billion years. Examinations of the cooling rate of stellar corpses called white dwarfs yielded an age of 12.7 billion years, give or take 700 million years. And a look at when stars within clusters stopped shining in their primary “main sequence” phase set the age at 12.6 billion years, but with a possible range from 10.4 billion to 16 billion years.

One thought on “Finding the age of a galaxy

  1. Awesome post my friend! This is all new stuff to me.

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