Question

Define solar luminosity.

Answer 1

Hint: The total power output of the Sun radiated to the space is known as solar luminosity. It is the unit of radiant flux that is power emitted in the form of photons, and is used by astronomers to measure the luminosity of stars, galaxies and other celestial bodies.

Complete step by step answer:
The solar luminosity, denoted by $L_{\odot }$ is a unit of radiant flux. Solar luminosity is related to the solar constant, or solar irradiance. Luminosity can be determined by measuring the total solar irradiance. By knowing the total solar irradiance and mean distance between the Sun and the Earth, we can easily calculate solar luminosity.

One of the most fundamental properties of stars like the Sun is that they radiate enormous amounts of energy into space. We can measure the energy output of the Sun and hence calculate the solar luminosity.

Solar constant is an important term while defining solar luminosity. Solar constant is the amount of solar energy falling on each square meter of the Earth’s upper atmosphere each second. This is basically related to the energy output of the Sun. The value of Solar constant is equal to 1400 Watts per square meter.

To find the value of solar luminosity, we can imagine placing the Sun in a sphere large enough to enclose it properly. Next step is to determine how much energy radiated by the Sun passes through the sphere. The amount of energy that passes through this sphere is known as solar luminosity.

Value of solar luminosity is approximately equal to$4\times {10}^{26}\text{Watts}$.

Note:
Solar luminosity is the total power output of the Sun radiated to the space while solar irradiance is the total power per unit area at a distance of $\text{1AU}$. SI unit of solar luminosity is Watt, while that of solar irradiance is Watt per square meter.