Luminosity to magnitude

  • #1
I am trying to find out how fast a star's magnitude changes over time, and have two columns of data.
The first is the time since the stay left the main sequence, and the second is Log (L/L_sun).

I am unsure as to how to chance the luminosity values into magnitudes, which means I cant answer the question.

I thought it might be m=2.5 log L but I dont know if this is correct or not.

If anyone can help it would be greatly appreciated

Thanks :D
 

Answers and Replies

  • #2
55
1
Depends whether you want apparent or absolute magnitude.
For apparent the formula would be
[itex]m_1 - m_2 = -2.5 \log{\frac{L_1}{L_2}}[/itex]
 
  • #3
But i'm not given actual luminosities, i've been given Log (L/L_sun)
so for example one of my values is 4.4799, how would i turn this into a magnitude?

And yes, I was looking for an apparent magnitude, forgot to mention it in my first post
 
  • #4
55
1
[itex]m_1 = m_{sun} - 2.5\log{\frac{L}{L_{sun}}}[/itex]
where [itex]m_{sun} = –26.74[/itex]

So for the value you gave you'd get
[itex]m_1 = -26.74 - 2.5*4.4799[/itex]
which gives a pretty high magnitude as the lower the magnitude, the brighter the object.
 

Related Threads on Luminosity to magnitude

Replies
2
Views
733
  • Last Post
Replies
0
Views
2K
  • Last Post
Replies
1
Views
2K
  • Last Post
Replies
1
Views
1K
  • Last Post
Replies
9
Views
662
  • Last Post
Replies
3
Views
2K
  • Last Post
Replies
1
Views
1K
  • Last Post
Replies
0
Views
989
  • Last Post
Replies
1
Views
768
Replies
3
Views
864
Top