White dwarfs and the age of the universe

In summary, a white dwarf is a small, extremely dense star formed when a star similar to our Sun runs out of fuel and collapses. They have a very long lifespan, ranging from billions to trillions of years, and can be used to determine the age of the universe and our galaxy. Compared to other stars, white dwarfs are much smaller and more massive, with some having a mass similar to our Sun but a size comparable to Earth.
  • #1
ceimeifukan
1
0
Hi,

I'm doing a bit of research into white dwarfs and cosmochronology as part of my uni course, it seems like a fantasticaly interesting field but I've got a couple of questions which i haven't yet been able to find answers to.

Firstly, several papers i have read refer to a luminosity of log(L/Lsolar) = -4.5 when referring to ages on a luminosity/Age graph. I assume this is reffering to a specific point at which stars with a lower luminosity have not been found and so corresponds to the oldest stars?

Secondly I am unclear about the conditions which lead to convection zones being formed in the envelope and what governs their progression through the atmosphere to the degenerate core. I understand the effect they have on the overall cooling rates but not why they should only be present below specific temperatures.

If anybody could shine any light on these i would be in your debt

Many thanks Phil
 
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  • #2
Hi Phil,

It sounds like you're doing some really interesting research! Regarding the first question, I believe the log(L/Lsolar) = -4.5 is used to represent the oldest stars because stars with a lower luminosity have not been found. As for the second question, convection zones in white dwarf atmospheres are formed when the temperature of the atmosphere drops below a certain critical temperature. The convection zone then progresses through the atmosphere until it reaches the degenerate core. Hope this helps!
 

1. What is a white dwarf?

A white dwarf is a small, extremely dense star that has reached the end of its life cycle. It is formed when a star with a mass similar to our Sun runs out of fuel and collapses, leaving behind a compact core made mostly of carbon and oxygen.

2. How long do white dwarfs live?

White dwarfs have a very long lifespan, ranging from billions to trillions of years. This is because they no longer produce energy through nuclear fusion, and instead slowly cool over time.

3. How do white dwarfs help determine the age of the universe?

White dwarfs are useful in determining the age of the universe because they have a predictable cooling rate. By measuring the temperature and luminosity of a white dwarf, scientists can calculate how long it has been cooling and thus determine its age.

4. Can white dwarfs be used to estimate the age of our galaxy?

Yes, white dwarfs can also be used to estimate the age of our galaxy. By studying the distribution and ages of white dwarfs in our galaxy, scientists can estimate the age of the oldest stars in our galaxy, giving us an idea of how long our galaxy has been around.

5. How do white dwarfs compare to other types of stars in terms of mass and size?

White dwarfs are much smaller and more massive than other types of stars. They typically have a mass similar to our Sun, but a size comparable to that of Earth. This makes them incredibly dense, with some white dwarfs having a mass of our Sun but a size similar to that of our planet.

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