Can Luminosity Give You a Star's Age?

In summary, two yellow stars at the same distance with the same mass can have different luminosities. While the luminosity of a star does increase somewhat with age, it would be a wildly unreliable way to determine the age of a star. The more massive star will have a different spectrum and will be hotter, even if their luminosity is the same. The graph provided on the sun's main sequence is approximately accurate, but the difference in luminosity over the course of the main sequence is not significant enough to be useful for estimating the age of a star.
  • #1
chefskitten
2
0
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?
 
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  • #2
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.
 
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  • #3
Thanks for your input howabout1337! That's what I was thinking, just wanted some confirmation
 
  • #4
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
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
phinds said:
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?

The more massive one has a different spectrum. It will be hotter, even if their luminosity is the same.
 
  • #7
Chronos said:
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.

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

544px-Solar_evolution_%28English%29.svg.png
 
  • #8
It's at least approximately right. When I studied these things, the sun went off the main sequence a little sooner and more quickly (9.1 BY), but there's a factor of ~2 or so luminosity increase over the course of the main sequence.
 
  • #9
When the sun first entered the main sequence, it was about 70% of its current luminosity. Over the next 4.5 billion years, it's luminosity is expected to increase by about 67%. I do not consider that enough of a luminosity difference to be useful to estimate the age of a star.
 

What is luminosity?

Luminosity is a measure of the total amount of energy emitted by a star per unit time. It is often used as an indicator of a star's size and brightness.

How can luminosity give you a star's age?

By measuring a star's luminosity and comparing it to known values for stars of similar mass, scientists can estimate the star's age. This is based on the understanding that stars go through predictable stages of evolution.

What other factors besides luminosity are used to determine a star's age?

Other factors that may be taken into account when estimating a star's age include its temperature, chemical composition, and location within its galaxy.

Can luminosity alone accurately determine a star's age?

No, luminosity is just one piece of the puzzle when it comes to estimating a star's age. It must be used in combination with other data and observations to get a more accurate estimation.

Why is knowing a star's age important?

Knowing a star's age can provide valuable information about the history and evolution of the universe. It can also help scientists understand the behavior and characteristics of stars at different stages of their lives.

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