Italian astronomers report the detection of a new X-ray binary (XRB), which has received the designation 4XMM J181330.1-17511 ...

Each class is subdivided into ten and numbered from 0 to 9. The Sun is a G2 star. The “V” is the Roman numeral for five and designates the Sun’s luminosity class. Stars in luminosity classes I, II, ...

The brighter the star is overall, the longer the period of luminosity. Since the cepheids in the Magellanic Clouds were all about the same distance from Earth, Leavitt concluded that the period ...