What is apparent brightness and absolute brightness in Science
http://www.answers.com/Q/What_is_difference_between_apparent_brightness_and_absolute_brightness
Apparent brightness and absolute brightness are terms used in astronomy to describe the brightness of celestial objects, such as stars. Let's break down these concepts:
1. Apparent Brightness: This refers to how bright a star appears to be when viewed from Earth. It is influenced by two primary factors: the star's actual luminosity (or total amount of energy it emits) and its distance from Earth.
To calculate the apparent brightness of a star, astronomers use a formula called the inverse square law. The inverse square law states that the apparent brightness is inversely proportional to the square of the distance:
Apparent Brightness ∝ (1 / Distance^2)
Therefore, as the distance between Earth and the star increases, its apparent brightness decreases. Similarly, if two stars have the same luminosity but different distances, the closer star will appear brighter.
2. Absolute Brightness: This refers to the actual luminosity of a star, regardless of its distance from Earth. In other words, it measures the star's intrinsic brightness. It is an important property to estimate a star's true power or energy output.
To determine the absolute brightness of a star, astronomers compare its apparent brightness to the known distances and absolute brightnesses of other stars. By using a standardized system and known reference stars, they can classify stars based on their absolute brightness.
The absolute brightness is often measured using a unit called the absolute magnitude (M). A star with a larger absolute magnitude is dimmer, while a star with a smaller absolute magnitude is brighter.
In summary, apparent brightness is how bright a star appears from Earth, influenced by its actual luminosity and distance. Absolute brightness, on the other hand, indicates the true luminosity of a star, independent of distance.