This isotope is found at a ratio of about one per 2,500 helium-4 ions, the latter being the common version of helium.

Skywatchers throughout the Northern Hemisphere are enjoying views of the newly discovered Comet SWAN.

They’re the guardians of the Solar System and Earth’s first line of defence. But now the agents of the Space Security Service ...

Named for Nancy Grace Roman, who served as NASA's first chief astronomer, it will be located approximately 1.5 million ...