# Combined apparent magnitude of a star cluster

Watch
Announcements
#1
Hi all, I've been set a question which asks for the combined apparent magnitude of a cluster of 25000 stars. 1000 of them have an apparent magnitude m = 12.0, and the other 24000 have m = 15.0.

So far I've calculated that the combined apparent magnitude of the set of 1000 stars is exactly 7, and for the 24000 it is approximately 4 (4.04947...). However, I don't know how to then combine these values for the whole cluster.

I've been using the equation:

Presumably I'll have to use this again, but the issue is I don't actually know how to calculate the luminosity/intensity required... Up until this point, the fractions have just cancelled to simple numbers without a prior calculation being needed. I've tried to search how to progress but nothing is making much sense to me Any help would be much appreciated.
0
#2
Surely someone has an idea? Please
0
5 years ago
#3
(Original post by velkyr)
Hi all, I've been set a question which asks for the combined apparent magnitude of a cluster of 25000 stars. 1000 of them have an apparent magnitude m = 12.0, and the other 24000 have m = 15.0.

So far I've calculated that the combined apparent magnitude of the set of 1000 stars is exactly 7, and for the 24000 it is approximately 4 (4.04947...). However, I don't know how to then combine these values for the whole cluster.

I've been using the equation:

Presumably I'll have to use this again, but the issue is I don't actually know how to calculate the luminosity/intensity required... Up until this point, the fractions have just cancelled to simple numbers without a prior calculation being needed. I've tried to search how to progress but nothing is making much sense to me Any help would be much appreciated.
I didn't do astrophysics in My A2 units so I really don't know how to approach the question. For what level is this? Is there an equation to calculate the luminosity/intensity? There are some Astrophysics notes online for AQA that might be of help.

Edit: perhaps this helps.

http://physics.unl.edu/~klee/ast204/...-solutions.pdf
0
#4
I didn't do astrophysics in My A2 units so I really don't know how to approach the question. For what level is this? Is there an equation to calculate the luminosity/intensity? There are some Astrophysics notes online for AQA that might be of help.

Edit: perhaps this helps.

http://physics.unl.edu/~klee/ast204/...-solutions.pdf
Hi, it's for first year undergraduate work.

I was using that question to help me through it but I don't know how the last part of it is done. Therein lies my issue.
0
#5
Nevermind, have sorted it by using another method now. Thanks anyway.
1
5 years ago
#6
(Original post by velkyr)
Nevermind, have sorted it by using another method now. Thanks anyway.
No worries! Glad you managed to figure it out as I really have no idea how to work that out.
0
X

new posts
Back
to top
Latest
My Feed

### Oops, nobody has postedin the last few hours.

Why not re-start the conversation?

see more

### See more of what you like onThe Student Room

You can personalise what you see on TSR. Tell us a little about yourself to get started.

### Poll

Join the discussion

#### How would you feel if uni students needed to be double vaccinated to start in Autumn?

I'd feel reassured about my own health (45)
15.15%
I'd feel reassured my learning may be less disrupted by isolations/lockdowns (95)
31.99%
I'd feel less anxious about being around large groups (37)
12.46%
I don't mind if others are vaccinated or not (26)
8.75%
I'm concerned it may disadvantage some students (17)
5.72%
I think it's an unfair expectation (74)
24.92%
Something else (tell us in the thread) (3)
1.01%