If the sun were as bright as the Milky Way galaxy, it would have to be 1.7 billion degrees Celsius. It would then have 25 sextillion times its current brightness and evaporate every planet in our solar system within milliseconds. The habitable zone would be 1.3 million light years away, which would take 25 quadrillion years for one orbit to complete. However, the sun would run out of hydrogen in 0.4 seconds.
