The brightest visible star in the night sky is Sirius (also known as the Dog Star).
For those of you astronomy buffs, Sirius has an apparent visual magnitude of 1.46 and a surface temperature of 9, 9940 Kelvin – about 4,000 Kelvin hotter than our Sun.
For you science buffs, Kelvin (K) is not referred to or written as “degrees.” Kelvin (K) is the base unit of thermodynamic temperature measurement in the International System of Units and the fundamental unit of the absolute temperature scale named for the British physicist William Thomson (known as Lord Kelvin).
This absolute temperature scale starts at absolute zero (which, translated into temperature we know would be −273.15° on the Celsius scale and −459.67° on the Fahrenheit scale).
Absolute zero is the theoretical temperature at which the molecules of a substance have the lowest energy and since the starting point of the kelvin scale is absolute zero, there are no negative values. In other words, in Kelvin, nothing can be below zero!