Thursday, July 14, 2011
Absolute Magnitude of a Star
Out of all the stars that we observe at night, it is easy to identify a certain few. Is it because they look brighter to us?
As observers on earth, we only notice the apparent magnitude (m) of the star. 
Astronomers often need to know how much light a star truly radiates into space. This is referred to as the star’s luminosity.The stars we see in the sky are oftentimes different distances away from us. 
Let’s imagine 2 stars which look equally bright to us. The further star has a greater luminosity, a greater absolute magnitude (M). The absolute magnitude of a star is the apparent magnitude that it would have if it were observed at a distance of 10 parsecs.
To fairly compare stars at different distances, scientists use the absolute magnitude formula:
M = m-5log(d/10)
Where:
M= absolute magnitude
m= apparent magnitude 
d= distance in parsecs*
*Note: A parsec is equivalent to 3.26 light years
Image is Star Cluster NGC 1850. [Image source]

Absolute Magnitude of a Star

Out of all the stars that we observe at night, it is easy to identify a certain few. Is it because they look brighter to us?

As observers on earth, we only notice the apparent magnitude (m) of the star. 

Astronomers often need to know how much light a star truly radiates into space. This is referred to as the star’s luminosity.The stars we see in the sky are oftentimes different distances away from us. 

Let’s imagine 2 stars which look equally bright to us. The further star has a greater luminosity, a greater absolute magnitude (M). The absolute magnitude of a star is the apparent magnitude that it would have if it were observed at a distance of 10 parsecs.

To fairly compare stars at different distances, scientists use the absolute magnitude formula:

M = m-5log(d/10)

Where:

M= absolute magnitude

m= apparent magnitude 

d= distance in parsecs*

*Note: A parsec is equivalent to 3.26 light years

Image is Star Cluster NGC 1850. [Image source]

Notes

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