An independent estimate of the minimum age of the universe can be found by assuming that the universe is older than anything in it. For example, we can estimate the age of the oldest stars that we see. These are found in globular clusters such as M15, which you can see on a clear summer night in the constellation of Hercules. By looking at the temperature and brightness or luminosity of stars in M15, and using theoretical stellar models, we find ages of order 14-15 billion years. This is uncomfortably close to the upper limit of the age of the universe as measured by the expansion time described above.
A third estimate is found by examining the population stellar remnants known as white dwarfs. These are the collapsed cores of stars that have exhausted their nuclear hydrogen fuel. Since they are no longer burning hydrogen into helium, they are cooling off. By measuring the temperatures of white dwarfs, and calculating the rate at which they cool off, astronomers estimate that the oldest white dwarfs in our galaxy are 10 billion years old.
Next: Lecture Two
Previous: List of Lectures
Back to the list of lectures.
Back to Geology 130 Home page.