G refers to the apparent magnitude[0] in the main filter used by the European Space Agency's Gaia space telescope (one of the most important scientific missions

G refers to the apparent magnitude[0] in the main filter used by the European Space Agency's Gaia space telescope (one of the most important scientific missions going on right now, though the public is less aware of it than, say, JWST).[1,2] pc refers to "parsec," a unit of distance approximately equal to 3.3 light years. Parsecs are a natural unit of distance, because a star that is one parsec away has a yearly parallax "wobble" of one arcsecond (not by accident - this is how the parsec is defined). Parallax is the fundamental way in which distances to nearby stars are measured, so parsecs are the natural unit to use. Every greater distance in astronomy is defined with reference to parsecs: kiloparsecs, Megaparsecs, Gigaparsecs, ... 0. https://en.wikipedia.org/wiki/Apparent_magnitude https://en.wikipedia.org/wiki/Apparent_magnitude 1. https://en.wikipedia.org/wiki/Gaia_(spacecraft) https://en.wikipedia.org/wiki/Gaia_(spacecraft) 2. https://www.esa.int/Science_Exploration/Space_Science/Gaia https://www.esa.int/Science_Exploration/Space_Science/Gaia