Final answer:
The highest luminosity star is the one that emits the most energy per second at all wavelengths, with luminosity varying among stars. Stars like Sirius can have luminosities many times that of the Sun, helping astronomers determine their lifespan and other characteristics.
Step-by-step explanation:
The star with the highest luminosity is the one that emits the most energy per second across all wavelengths. Luminosity is a fundamental characteristic of stars, reflecting their intrinsic brightness, which is independent of their distance from us. A key point to note is that stars are not standard bulbs with uniform wattage, hence their luminosity varies greatly. For example, the luminosity of Sirius is about 25 times that of our Sun, denoted as 25 Lsun. The energy released by stars can vary from less than that of the Sun to many times greater. To demonstrate, we assess luminosity in terms of comparisons to the Sun's output, allowing for a clearer understanding of a star's true energy emission capabilities. These measurements help astronomers calculate how long a star might continue to shine before its nuclear energy is exhausted.