What is the White Dwarf Cooling Curve and how can it be used to determine the age of our galaxy?

Question

What is the White Dwarf Cooling Curve and how can it be used to determine the age of our galaxy?

Oh, and could you add sources for your answer, preferably links?

Answer 1

White dwarves are all about the same mass and surface area(*) and they do not generate any new energy (with the exception of white dwarves in close binary systems) so their surface temperature is well correlated with age. With no new energy input they cool steadily over time. The oldest white dwarves will also be the coolest. Working backwards from their temperatures you can calculate when they formed as white dwarves. The cooling curve would be a plot of temperature vs. time. Add a billion years so that these guys spent on the main sequence and you have the age at when they formed.

Assuming that the first burst of star formation in the galaxy formed a whole range of masses, then the coolest white dwarves would have formed as stars around that time and so their age is the "age of the galaxy" depending on how you define the beginning of our galaxy.

For a variety of reasons this technique is not super precise, but it'll get you there within 20% which is pretty good for astronomy.


I just know this stuff because I have a graduate education in astronomy, but I'll cook up a source or three for you.

http://adsabs.harvard.edu/cgi-bin/nph-bib_query?bibcode=1987ApJ...315L..77W&db_key=AST&data_type=HTML&format=&high=42eba12e0f08656

(*) The "same mass" part has a caveat. As the galaxy grows older, lower and lower mass stars will reach the end of their lives making for lower and lower mass white dwarf populations. (Lower mass stars live longer).

Answer 2

White Dwarf Cooling

Answer 3

True for most people but some people don't care what others think and they just make mistakes but I think it is too do with confidence and if someone makes a mistake they may feel embarrassed or that someone might make fun of him/her. Although some people don't learn from their mistakes..