# Can Luminosity Give You a Star's Age?

1. Oct 25, 2013

### chefskitten

You find two yellow stars at the same distance (but not in a binary system!). They have the same mass, but one is much more luminous than the other.
Which one is older?

2. Oct 26, 2013

http://en.wikipedia.org/wiki/Stellar_age_estimation: [Broken]
"As stars grow older, their luminosity increases at an appreciable rate"

So I would assume the more luminous one.

Last edited by a moderator: May 6, 2017
3. Oct 27, 2013

### chefskitten

Thanks for your input howabout1337! That's what I was thinking, just wanted some confirmation

4. Oct 27, 2013

### phinds

I don't get it. How would you tell an old modest-sized star from a large younger star, both of which have the same luminosity?

5. Oct 27, 2013

### Chronos

The luminosity of a star is strongly dependent on mass, which is known as the mass-luminosity relationship. While the luminosity of a star does increase somewhat with age, the difference is small until it leaves the main sequence. It would be a wildly unreliable way to determine the age of a star.

6. Oct 28, 2013

### Drakkith

Staff Emeritus
The more massive one has a different spectrum. It will be hotter, even if their luminosity is the same.

7. Oct 28, 2013

### Drakkith

Staff Emeritus
Do you know if this graph is accurate? This seems to be a pretty big change.
From here: http://en.wikipedia.org/wiki/Sun#Main_sequence

8. Oct 28, 2013