The youngest and most metal-rich stars, such as the Sun, are called Population I. Older stars with fewer metals are Population II. The oldest stars, the very first stars to appear in the Universe, are ...
Astronomers have detected fast-repeating radio bursts from a distant "dead" galaxy that should not contain the energy to produce these types of signals.
A hundred years ago, astronomer Edwin Hubble dramatically expanded the size of the known universe. At a meeting of the American Astronomical Society ...
In 1920, astronomers Harlow Shapley and Heber Curtis held a Great Debate. Shapley argued that the spiral nebulae were small and in the Milky Way, while Curtis took a more radical position that they ...