M100

This spiral galaxy currently holds a unique distinction in that it is one of the furthest galaxies in which Cepheid variables have been detected. These special variable stars have a specific relationship between their period of variation and brightness. Astronomers measure the periods of these stars to learn how bright they are. By knowing how bright the star truly is and how bright it appears, astronomers can measure their distance from Earth. In general galaxies are so far away even the best telescopes in the world cannot resolve individual stars. However in some of our nearby galactic neighbors it is possible. From these measurements M100 is estimated to be 56 million light years away.

This image was taken as part of Advanced Observing Program (AOP) program at Kitt Peak Visitor Center during 2014.