Finding flux from apparent and absolute magnitude

In summary, the conversation discusses the concept of flux and how it is affected by the relationship between apparent and absolute magnitudes. It is mentioned that two stars with the same absolute magnitude will have the same luminosity, but calculating the flux independently requires a reference point. Without a reference point, it is impossible to determine the flux of each star.
  • #1
sikrut
49
1
How much flux reaches Earth from an unobscured star?

##m_{sun} = -26.83## and ##M_{sun} = +4.74##
##m = +6## and ##M = +4.74##

Calculated distance of target star:

##d = 17.86 pc##

Now, here I'm trying to find the flux of a star that has the same absolute magnitude as our sun, but has an apparent magnitude of 6.

Does it make sense to assume that because their absolute mags are the same, that the ratio of their luminosities should be 1? Further more, under that assumption, I understand how to calculate the ratio of their fluxes (sun to star), but I am a bit lost when trying to calculate their fluxes independently...
 
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  • #2
Yes, if the stars have the same absolute magnitude, they have the same luminosity.
 
  • #3
You can't calculate the flux from apparent magnitude independently. You need some reference point. The apparent magnitudes of two sources are related by
$$m - m_\text{ref} = -2.5 \log \frac{F}{F_\text{ref}}$$ where F is the flux and the subscript ref refers to a known reference.
 
  • #4
But what if the absolute magnitudes and distances of those stars are known?
 
  • #5
Is there not some way to manipulate the flux ratio so that you can calculate the fluxes of each star?
 
  • #6
No. If all you have is, for example, ##F/F_\text{ref} = 2##, there's no way to differentiate between the case where (neglecting units) ##F=1## and ##F_\text{ref} = 1/2## and where ##F=2## and ##F_\text{ref}=1##. You have only one equation but two unknowns.
 
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What is the difference between apparent and absolute magnitude?

The apparent magnitude of an object is a measure of its brightness as seen from Earth, while absolute magnitude is a measure of its intrinsic brightness, independent of its distance from Earth. Apparent magnitude takes into account the object's distance and the absorption of light by interstellar dust, whereas absolute magnitude is solely based on the object's luminosity.

How are apparent and absolute magnitude related to flux?

Apparent and absolute magnitude are not directly related to flux. Flux is a measure of the amount of light energy passing through a unit area per unit time. However, apparent and absolute magnitude can be used to calculate flux using the inverse square law, which states that the apparent brightness of an object decreases in proportion to the square of its distance.

What is the formula for finding flux using apparent and absolute magnitude?

The formula for finding flux using apparent and absolute magnitude is: flux = 10^((absolute magnitude - apparent magnitude)/2.5). This formula takes into account the difference in brightness caused by the object's distance and absorption of light by interstellar dust.

Why is it important to calculate flux from apparent and absolute magnitude?

Calculating flux from apparent and absolute magnitude allows us to compare the intrinsic brightness of objects at different distances. This is especially important in astronomy, where objects can vary greatly in their distances from Earth. It also allows us to better understand the properties and characteristics of celestial objects.

What are some factors that can affect the flux calculated from apparent and absolute magnitude?

Some factors that can affect the flux calculated from apparent and absolute magnitude include the object's distance, the absorption of light by interstellar dust, and the accuracy of the measurements of apparent and absolute magnitude. The inverse square law also assumes that the object is a point source, so the size and shape of the object can also affect the calculated flux.

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