Can two stars have the same apparent but different absolute magnitudes

In summary: When two stars have the same absolute magnitude but different apparent magnitudes, the brighter star is farther from us and will appear fainter. However, if two stars have the same absolute magnitude but different extinction values, then they will have the same apparent magnitude.
  • #1
bse
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Can two stars have the same apparent magnitudes but different absolute magnitudes?

what about if two stars have the same absolute magnitudes but different apparent magnitudes?
 
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  • #2
Yes to both. Absolute magnitude is independent of distance (how far the star is from us), while apparent magnitude does depend on distance. A bright star very far from us will appear fainter than a less bright star very close to us.

For two stars with different absolute magnitudes to have the same apparent magnitude, the fainter star could be nearer to us and the brighter star could be farther from us.

For two stars with the same absolutely magnitude but different apparent magnitude, one star could be farther than the other.

Extinction (the absorption or scattering of light) also affects apparent magnitude by making a star appear dimmer.
 
  • #3
Yes the two can have same absolute intensity and different relative magnitudes and vice versa.

As the light travels it spreads, and hence the intensity of light reaching the Earth lessens.
For a star near to us this spreading would be less and for a distant one would be more.So the star far away would seem to be fainter even if it has the same absolute intensity.
 
  • #4
Apparent magnitude is the luminosity of any given star viewed from earth. Absolute magnitude is the comparative luminosity of stars viewed from the same distance.
 
  • #5
Question

Could you please elaborate on the absolute intensity scale.
What is chosen as its base line or reference point??
 
  • #6
anonymoussome said:
Could you please elaborate on the absolute intensity scale.
What is chosen as its base line or reference point??

Absolute magnitude is the visual magnitude the star would have at a distance of 10 parsecs(32.616 lightyears)
 
  • #7
anonymoussome said:
Could you please elaborate on the absolute intensity scale.
What is chosen as its base line or reference point??

The absolute magnitude of a star is the apparent magnitude that the star would have if it were at a distance of 10 parsecs from the Earth, i.e., for stars at 10 parsecs,

absolute magnitude = apparaent magnitude.

[edit]Somehow (went some time without refreshing), I missed the reply by Janus[/edit]
 

1. Can two stars have the same apparent magnitude but different absolute magnitudes?

Yes, it is possible for two stars to have the same apparent magnitude but different absolute magnitudes. This is because apparent magnitude is a measure of how bright a star appears from Earth, while absolute magnitude is a measure of the star's intrinsic brightness.

2. How is apparent magnitude different from absolute magnitude?

Apparent magnitude is a measure of how bright a star appears from Earth, taking into account factors such as distance. Absolute magnitude, on the other hand, is a measure of the star's intrinsic brightness and is not affected by distance.

3. How do scientists determine the apparent and absolute magnitudes of stars?

Scientists use a photometer to measure the apparent magnitude of a star, which measures the amount of light received from the star. To determine the absolute magnitude, they also need to know the distance to the star, which can be determined through methods such as parallax or spectroscopic measurements.

4. Can the apparent magnitude of a star change over time?

Yes, the apparent magnitude of a star can change over time. This can be due to various factors such as the star's own variability, changes in the Earth's atmosphere, or the presence of other objects that can affect the amount of light reaching Earth from the star.

5. Why is it important for scientists to know both the apparent and absolute magnitudes of a star?

Knowing both the apparent and absolute magnitudes of a star allows scientists to calculate its distance from Earth and understand its true brightness. This information is crucial for studying the properties and evolution of stars, as well as for determining the structure and scale of the universe.

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