# Absolute Visual Magnitude of Stars

• Jimbob999
The answer is indeed closest to a), with a difference of only 9% from b), so it's understandable that you might want to double check your work.
Jimbob999

## Homework Statement

The Sun has an absolute visual magnitude of about 4.8 and a particular star has an absolute visual magnitude of –0.29. How many times more luminous is this star than the Sun, assuming these stars have similar spectral types and hence colours?

a) 100 times
b) 125 times
c) 150 times
d) 175 times
e) 200 times

## Homework Equations

Luminosity of Star 1/ Luminosity of Star 2 = (100^1/5)^M2-M1
Where M1 and M2 are the abolute magnitudes

## The Attempt at a Solution

[/B]
2.51^(4.81--0.29)
= 109 times more luminous

I am just wondering whether I have calculated correctly, given my answer is closest to a) but nearly crossing over to b)

Your calculations appear to be okay to me (although you've used 4.81 rather than the given 4.8 for the Sun's absolute magnitude, a minor quibble that doesn't significantly impact your query).

## 1. What is the absolute visual magnitude of a star?

The absolute visual magnitude of a star is a measure of its intrinsic brightness, or how bright it appears from a standard distance of 10 parsecs (32.6 light years) away. It takes into account the star's luminosity, or total energy output, and is independent of its distance from Earth.

## 2. How is absolute visual magnitude different from apparent magnitude?

Apparent magnitude is a measure of how bright a star appears from Earth, while absolute visual magnitude is a measure of its intrinsic brightness. Apparent magnitude takes into account a star's distance from Earth, while absolute visual magnitude does not.

## 3. What is the scale used to measure absolute visual magnitude?

The scale used to measure absolute visual magnitude is known as the absolute magnitude scale, and it is based on the difference in brightness between a star and the Sun. The lower the absolute magnitude, the brighter the star.

## 4. How is the absolute visual magnitude of a star calculated?

The absolute visual magnitude of a star can be calculated using the formula M = m - 5log(d/10), where M is the absolute magnitude, m is the apparent magnitude, and d is the distance to the star in parsecs. This formula takes into account the inverse square law, which states that the brightness of an object decreases with the square of its distance from the observer.

## 5. Why is the absolute visual magnitude of a star important to astronomers?

The absolute visual magnitude of a star is important to astronomers because it allows them to compare the intrinsic brightness of stars, regardless of their distance from Earth. This helps in understanding the true nature and characteristics of stars, and is crucial in studying their evolution and behavior.

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