Russell drew a simple system of coordinates with x- and y-axes, familiar to schoolchildren from geometry lessons. On this diagram, he entered the stars according to their spectral type or temperature ...

Hubble proved Andromeda is a separate galaxy by identifying a Cepheid variable star within it. Cepheid variables have a period-luminosity relationship: longer period means greater brightness. Knowing ...

Cepheid variable stars exhibit regular pulsations whose period directly correlates with their intrinsic brightness (absolute luminosity). The Leavitt law establishes this relationship between ...

WE have shown 1 that the impression of brightness produced by a light ray which forms an image on a fixed area of the retina depends in high degree on the position of entry of the ray in the eye pupil ...

A glance at the night sky above Earth shows that some stars are much brighter than others. However, the brightness of a star depends on its composition and how far it is from the planet. Astronomers ...

Since May 24, 2019, SpaceX has been launching satellites into orbit 60 at a time to bolster the ranks of its Starlink megaconstellation – a fleet of networked sats flying in formation that, once ...

One of the trickiest problems in astronomy is the measure of distance. In theory, distance should be simple to work out. If you know the intrinsic brightness of an object, a simple measure of its ...