Apparent magnitude is a measure of the brightness of a celestial object as seen from Earth. The lower the number, the brighter the object. Negative numbers indicate extreme brightness. We can see objects up to 6th magnitude without a telescope.
Apparent magnitude is abbreviated m.
This system of rating the brightness of celestial objects was developed by the Greek astronomer Hipparchus in 120 B.C. Absolute magnitude is a measure of the inherent brightness of a celestial object. The lower the number, the brighter the object. Negative numbers indicate extreme brightness. Antares is a M1.5Iab variable red supergiant star that is about 520 light-years from Earth and is about 230 times as big as the Sun . Arcturus is 34 light-years from Earth.