Enter the brightness of the star and the brightness of the reference star into the calculator to determine the magnitude. This calculator can also evaluate any of the variables given the others are known.

## Star Magnitude Formula

The following formula is used to calculate the brightness of a star in terms of its magnitude.

M = -2.5 * log(B / B0)

Variables:

- M is the magnitude of the star
- B is the brightness of the star
- B0 is the brightness of a reference star (usually Vega, with a magnitude of 0)

To calculate the magnitude of a star, take the logarithm (base 10) of the ratio of the star’s brightness to the brightness of the reference star. Multiply this result by -2.5 to account for the inverted scale and the logarithmic nature of the magnitude system. The result is the magnitude of the star, with lower numbers indicating brighter stars.

## What is a Star Magnitude?

Star magnitude is a system used by astronomers to measure the brightness of stars, planets, and other celestial objects. The system is logarithmic, meaning that each level of magnitude is 2.5 times brighter than the previous one. The scale is also inverted, so a star with a lower magnitude number is actually brighter than one with a higher number. For example, a star with a magnitude of 1 is 2.5 times brighter than a star with a magnitude of 2. This system allows astronomers to compare the brightness of different celestial objects.

## How to Calculate Star Magnitude?

The following steps outline how to calculate the Star Magnitude using the given formula:

- First, determine the brightness of the star (B).
- Next, determine the brightness of the reference star (B0).
- Next, substitute the values of B and B0 into the formula: M = -2.5 * log(B / B0).
- Finally, calculate the magnitude of the star (M).
- After inserting the variables and calculating the result, check your answer with the calculator above.

**Example Problem:**

Use the following variables as an example problem to test your knowledge:

brightness of the star (B) = 100

brightness of the reference star (B0) = 1