An astronomer needs to measure the distance to a globular cluster of stars that is part of the Milky Way Galaxy. What method should she try to use to find the distance?

Question

Quizplus · Accepted Answer

The best method for measuring the distance to the globular cluster is to find a variable star (either a cepheid or RR Lyrae) in the cluster. These types of stars have a predictable relationship between their luminosity and pulsation period, allowing astronomers to use them as "standard candles" to determine the distance. Measuring the parallax of the cluster or the red-shift of the stars would not be possible due to the great distances involved, counting the number of O and B type stars is not a reliable distance indicator, and looking for flickering x-rays from a black hole in a binary star system would not provide accurate distance measurements.

An Astronomer Needs to Measure the Distance to a Globular