One million alien visitors from another star system could already be lurking in the solar system. We aren't talking about "little green men" here, however — more "little (and not so little) gray rocks ...

Solar power, once a 19th-century curiosity, is now the fastest-growing and increasingly the cheapest energy source worldwide. Key breakthroughs, like silicon-based solar cells and falling costs due to ...

The NASA New Horizons spacecraft's extensive observations of Lyman-alpha emissions have resulted in the first-ever map from the galaxy at this important ultraviolet wavelength, providing a new look at ...