the White Dwarf clock

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the White Dwarf clock

Postby hyksos on September 2nd, 2017, 10:02 am 

White dwarfs are remnants of stars which have since completed their life cycle. Most of them are composed of a hot lump of carbon and oxygen. A minority of them contain magnesium and neon , depending on mass.

Since the remnant no longer produces its own energy, it is expected to slowly cool as it radiates away light. After so many billions of years, a white dwarf should cool to a temperature where it no longer emits light, becoming a so-called Black Dwarf.

In the course of cosmology, we might observe white dwarfs of various temperatures, which have cooled a little but not completely to become black. Imagine a scenario in which no black dwarfs are ever observed, while the measured temperatures of white dwarfs has a suspicious "cut off point" of temperature, below which no dwarfs are seen radiating lower temperatures.

If such a scenario were confirmed by observation -- this would stand as the most stark evidence that the universe had a beginning in the recent past. The "cut off point" of temperatures of white dwarfs could be used as a sort of clock -- a cosmic egg timer -- that could be consistent or inconsistent with the 13.8 billion year estimate given by other means.

A strange lower-bound on temperatures of white dwarfs would be the most ironclad argument for the Big Bang.

Image
If anyone has a youtube lecture where such a graph of temperatures and a "cut off point" is demonstrated, feel free to reply below.
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Re: the White Dwarf clock

Postby JMP1958 on September 2nd, 2017, 11:30 am 

It takes trillions of years, not billions, for a white dwarf to cool and become a black dwarf. The coolest white dwarf found to date has a temp of 3900K.
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Re: the White Dwarf clock

Postby hyksos on September 2nd, 2017, 2:08 pm 

JMP1958,

Mathematically, we could actually graph what both scenarios would look like. We get the decay curve for the average dwarf temperature plotted against time. First suppose the universe is infinitely old into the past. We would get a certain clustering of curves at all temperature levels, all way to black.

If we were to place an artificial bound in the past at 13.8 bya, then the present moment of the graphs would have a distinct "cut off point" below which no dwarf is found at that temperature or lower. Enough data would show this to some sigma level of confidence (-- ie not resulting from bias introduced by low sampling error).

I don't have time to draw the graph today. It would look like exponential decay curves common to physics of cooling objects.

http://www.wolframalpha.com/input/?i=real+plot+f(t)+%3D+t%5E(-2.45)
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Re: the White Dwarf clock

Postby hyksos on September 10th, 2017, 8:41 am 

Oh zoinks.

whitedwarfdata.png
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