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.
Historical brightest stars
Working out exactly which stars were or will be the brightest at any given point in the past or future is difficult since it requires precise 3D proper motions of large numbers of stars and precise distances. This information only started to become available with the 1997 Hipparcos data release. Jocelyn Tomkin used this data to compile a list of brightest star in Earth's night sky at each period within the last or next 5 million years. Reanalysis of the Hipparcos data and new data from Gaia have rendered the list somewhat outdated. For example it doesn't include Gliese 710 which in about 1.35 million years time is expected to be close enough to have a magnitude of -2.7.