<p>The absolute luminosity of A is bigger than B. Like two lamps.
<span class="math-container">$$\frac{120}{24}=5,$$</span>
so A is five times farther B, but as the luminosity decays with the square of the distance, then  A is <span class="math-container">$5^{2}=25$</span> times more luminous.</p>

CC BY-SA 4.0
2019-02-01T21:13:38.500Z
Where did you get the 24?
James 9779
CC BY-SA 4.0
2019-02-01T21:14:43.790Z
Nevermind! I'm sorry, I'm overthinking. This makes since and is much simpler to understand this way.
James 9779
CC BY-SA 4.0
2019-02-01T21:16:36.413Z
I was trying to use the Inverse Square Law which is much harder to understand.
James 9779
CC BY-SA 4.0
2019-02-02T06:54:28.310Z
James, you might also like to read Wikipedia's page on [absolute magnitude](https://en.wikipedia.org/wiki/Absolute_magnitude) which is about being able to compare the luminosity of stars at different distances. :-)
Chappo Hasn't Forgotten
CC BY-SA 4.0
2019-02-01T19:20:57.647Z
2019-02-01T19:20:57.647Z
Gabriel Palau
<p>Stars A and B are both equally bright as seen from Earth, but A is 120 pc away while B is 24 pc away. Which star has the greater luminosity? How many times brighter is it?</p>

<fundamental-astronomy>
The Luminosity of two stars with same brightness but at different PC away
James 9779
# The Luminosity of two stars with same brightness but at different PC away

(Asked by: username_0 on 2019-02-01)

Stars A and B are both equally bright as seen from Earth, but A is 120 pc away while B is 24 pc away. Which star has the greater luminosity? How many times brighter is it?

**Tags:** fundamental-astronomy


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## 1 answers

### Answer by username_1 on 2019-02-01. Score: 1 | Accepted answer

The absolute luminosity of A is bigger than B. Like two lamps.
$$\frac{120}{24}=5,$$
so A is five times farther B, but as the luminosity decays with the square of the distance, then A is $5^{2}=25$ times more luminous.

> **Comments:**
> **username_0**: Where did you get the 24?  
> **username_0**: Nevermind! I'm sorry, I'm overthinking. This makes since and is much simpler to understand this way.  
> **username_0**: I was trying to use the Inverse Square Law which is much harder to understand.  
> **username_2**: James, you might also like to read Wikipedia's page on [absolute magnitude](https://en.wikipedia.org/wiki/Absolute_magnitude) which is about being able to compare the luminosity of stars at different distances. :-)  

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