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m1omg
2011-Jan-03, 11:56 PM
How fast do white dwarfs cool? How does it depend on mass and are high mass white dwarfs hotter? How long would it take for a 0.5 Solar mass (like the one that is supposed to result from the Sun) white dwarf to cool to: 10 000 K, 7000 K, 5000 K, 4000 K, 3000 K, 2500 K, 1000K, 800 K, 500 K and 300 K? How can it be calculated and does the degenerate matter state of the white dwarf somehow slow down the cooling process? This Wikipedia article cites a reference http://en.wikipedia.org/wiki/Black_dwarf that suggests 10 to the 15th years is the time until which white dwarfs will cool to 5 K, however by WIMP annihilation they might be kept at 63 K for a very long period of time (dwarfing the current age of the universe). Considering that the oldest WDs have already cooled to around 4000 K, how does the cooling rate slow? I assume that it cools very quickly at the beginning, then it takes almost infinity years to cool further. Am I correct?

StupendousMan
2011-Jan-04, 02:11 AM
The result of an ADS search using title words "white dwarf cooling rate" (http://adsabs.harvard.edu/cgi-bin/nph-abs_connect?db_key=AST&db_key=PRE&qform=AST&arxiv_sel=astro-ph&arxiv_sel=cond-mat&arxiv_sel=cs&arxiv_sel=gr-qc&arxiv_sel=hep-ex&arxiv_sel=hep-lat&arxiv_sel=hep-ph&arxiv_sel=hep-th&arxiv_sel=math&arxiv_sel=math-ph&arxiv_sel=nlin&arxiv_sel=nucl-ex&arxiv_sel=nucl-th&arxiv_sel=physics&arxiv_sel=quant-ph&arxiv_sel=q-bio&sim_query=YES&ned_query=YES&adsobj_query=YES&aut_logic=OR&obj_logic=OR&author=&object=&start_mon=&start_year=&end_mon=&end_year=&ttl_logic=OR&title=whote+dwarf+cooling+rate&txt_logic=OR&text=&nr_to_return=200&start_nr=1&jou_pick=ALL&ref_stems=&data_and=ALL&group_and=ALL&start_entry_day=&start_entry_mon=&start_entry_year=&end_entry_day=&end_entry_mon=&end_entry_year=&min_score=&sort=SCORE&data_type=SHORT&aut_syn=YES&ttl_syn=YES&txt_syn=YES&aut_wt=1.0&obj_wt=1.0&ttl_wt=0.3&txt_wt=3.0&aut_wgt=YES&obj_wgt=YES&ttl_wgt=YES&txt_wgt=YES&ttl_sco=YES&txt_sco=YES&version=1)

neilzero
2011-Jan-12, 05:36 AM
I read many of the titles supplied by StupendousMan. It occurs to me that our sun is called a yellow dwarf, so brown dwarf may be a sub class m star that did not make main sequence, instead of a compact star.
Almost neutron star mass should be hotter than white dwarfs with 20% less mass, but not always. I'll guess the Kalvin temperature drops by half in 2 billion years, but that is still white hot. Cool may mean lots hotter than the photosphere of our sun at present. A white dwarf radiates photons into space from an area about the same as our Earth, so it cannot cool quickly, with 1/2 million times more mass than our Earth. Neil