Star
The Sun has an apparent magnitude of −26.7, but its absolute magnitude is only +4.83. Sirius, the brightest star in the night sky as seen from Earth, is approximately 23 times more luminous than the Sun, while Canopus, the second brightest star in the night sky with an absolute magnitude of −5.53, is approximately 14,000 times more luminous than the Sun. Despite Canopus being vastly more luminous than Sirius, however, Sirius appears brighter than Canopus. This is because Sirius is merely 8.6 light-years from the Earth, while Canopus is much farther away at a distance of 310 light-years.
R136a1
At around , R136a1 is the most luminous star known, radiating more energy in four seconds than the Sun does in a year. If it replaced the Sun in the Solar System, it would outshine the Sun by 94,000 times (M = −7.6) and would appear from Earth at magnitude −39. Its brightness at a distance of 10 parsecs, the absolute visual magnitude, is −7.6, three magnitudes brighter than Venus ever appears from Earth. Its brightness at the distance of the nearest star to Earth, Proxima Centauri (just over a parsec), would be about the same as the full Moon.