Question

One of the basic properties used to characterize stars, luminosity is defined as the total energy radiated by the star each second, at all wavelengths is _____.

a) Solar constant
b) Solar wind
c) Solar flare
d) Luminosity

Answer 1

Luminosity is a measure of the total energy a star emits per second and is key in comparing stars. Astronomers express luminosities in terms of the Sun's output, with Sirius being 25 times more luminous than the Sun.

Step-by-step explanation:

Luminosity is defined as the total energy radiated by a star each second, at all wavelengths. This characteristic is a critical factor in the comparison of stars, which is why astronomers often express the luminosity of different stars in terms of the Sun's luminosity, denoted as Lsun. For instance, the luminosity of Sirius is about 25 times that of the Sun, expressed as 25 Lsun. Furthermore, understanding a star's luminosity is essential because it can provide insights into the star's lifespan and the nuclear processes occurring within it. Apparent brightness, on the other hand, is how bright a star appears from Earth and depends on both its luminosity and its distance from us.