Discovery of “variable stars” could help astronomers map dark matter in the galaxy
R.M. Catchpole/Institute of Astronomy/Univ. of Cambridge, JPL-Caltech/NASA
Beyond the galaxy’s center lie mostly uncharted swaths of space. But now astronomers have found some landmarks: five stars roughly 75,000 light-years from Earth. The discovery should help astronomers map the largely unexplored far side of the Milky Way and understand the nature of the enigmatic dark matter thought to hold galaxies together.
The five stars are all Cepheid variables, whose brightness fluctuates steadily. Astronomers use Cepheids as distance markers because the brighter the star, the slower it pulsates. By measuring a Cepheid’s period and how bright it appears from Earth, astronomers can calculate its distance; if the star is in another galaxy, then researchers know how far away the galaxy is as well.
Michael Feast, an astronomer at the University of Cape Town in South Africa, and colleagues found the stars in data from the Optical Gravitational Lensing Experiment, a telescope in Chile. The instrument