Cepheids are rare variable stars with periods ranging from about 1 to 120 days. Their light curve — a chart showing brightness over time — is characterized by rapid brightening followed by slow ...

The expansion of the Universe, discovered nearly a century ago by Edwin Hubble, shows that galaxies are moving away from us faster the more distant they are. Yet, our nearest neighbor, the ...

A sheet of dark matter lying beyond the boundary of the Local Group is responsible for this.

For centuries, people thought that the Milky Way was the edge of our universe. That was, until Edwin Hubble found a variable star in the Andromeda galaxy and we were able to literally expand our ...