# black dwarfs **URL:** \ **Category:** Factual Questions\ **Created:** [April 22, 2003, 6:59pm UTC](https://boards.straightdope.com/t/black-dwarfs/170378 "2003-04-22T18:59:05Z")\ **Posts on this page:** 4\ **Page:** 1
**Author:** ![owlofcreamcheese](https://avatars.discourse-cdn.com/v4/letter/o/97f17d/32.png) [@owlofcreamcheese](https://boards.straightdope.com/u/owlofcreamcheese)\ **Post date:** [April 22, 2003, 6:59pm UTC](https://boards.straightdope.com/t/black-dwarfs/170378/1 "2003-04-22T18:59:05Z")
no not negro midgets. I am always reading old science fiction, and nodiced that ‘black dwarfs’ seem like they were a concept for a while, following the ‘red dwarf’ ‘brown dwarf’ pattern. now we know that something dense enough becomes a black hole, which has all sorts of weird propertys. are black dwarfs totally out of the picture though? is every object with an escape velocity greater than the speed of light a black hole, singularity and everything? how about things with an escape velocity percisely equal to the speed of light? what about an object just one atom’s worth too little mass to have an EV of the speed of light? .9999999999999C or something? what about something with an escape velocity of .95C or so it would basicly absorb all the light other than light comeing perpendicularly to the surface. basicly my questions are: do black dwarfs exist at the edge right before black holes what do we call them now (neutron stars?) what sort of propertys do they have? ---
**Author:** ![Q.E.D](https://avatars.discourse-cdn.com/v4/letter/q/51bf81/32.png) [@Q.E.D](https://boards.straightdope.com/u/Q.E.D)\ **Post date:** [April 22, 2003, 7:36pm UTC](https://boards.straightdope.com/t/black-dwarfs/170378/2 "2003-04-22T19:36:16Z")
Yes, they’re called neutron stars now. They’re being kept from collapsing due to the nuclear strong force (as opposed to ordinary starts which are kept from collapsing due to the electroweak force), which is the last barricade before gravity overwhelms all, and the body crushes into a black hole. ---
**Author:** ![Grey](https://avatars.discourse-cdn.com/v4/letter/g/b782af/32.png) [@Grey](https://boards.straightdope.com/u/Grey)\ **Post date:** [April 22, 2003, 7:46pm UTC](https://boards.straightdope.com/t/black-dwarfs/170378/3 "2003-04-22T19:46:10Z")
I think the OP referes to completely cooled dwarf stars. From [http://imagine.gsfc.nasa.gov/docs/science/know\_l1/dwarfs.html](http://imagine.gsfc.nasa.gov/docs/science/know_l1/dwarfs.html) > [@](#): > > Eventually they, like our Sun, will cool down, radiating heat into space, fading into black lumps of carbon. It has taken 10 billion years, but our Sun has reached the end of the line and quietly become a black dwarf. > White dwarfs can tell us important things about the age of the universe. If we can estimate the time it takes for a white dwarf to cool into a black dwarf, that would give us a lower limit on the age of the universe and our galaxy. Because it takes billions of years for white dwarfs to cool, we don’t think the universe is old enough yet for many, if any, white dwarfs to have become black dwarfs. ---
**Author:** ![Chronos](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/chronos/32/134_2.png) [@Chronos](https://boards.straightdope.com/u/Chronos)\ **Post date:** [April 22, 2003, 8:11pm UTC](https://boards.straightdope.com/t/black-dwarfs/170378/4 "2003-04-22T20:11:02Z")
A red dwarf will also eventually become a (different sort of) black dwarf, but while there probably aren’t many white-dwarfs-turned-black in the Universe, there definitely aren’t any red-dwarfs-turned-black yet. Red dwarfs can live for literally trillions of years, and we’re quite certain that the Universe isn’t anywhere near that old.