Galaxy's

All objects in the Galaxy revolve around the Galaxy's center.

The Hubble Constant defines the relationship between a galaxy's distance from the Earth and the speed with which the galaxy is moving away from the Earth.

Scientists at the Harvard-Smithsonian Center for Astrophysics, after analyzing data from NASA's Kepler space telescope, calculated that six percent of the galaxy's 75 billion red dwarf stars have potentially habitable, Earth-sized planets. Red dwarfs — which are smaller, cooler and much dimmer than our own Sun — are the most common stars in the galaxy, so the closest Earth-like planet could be just 13 light years away, the astronomers conclude in their new study.