a quote from In the Night Sky: Orion

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Here's a quote from In the Night Sky:  Orion:

White dwarfs are the remains of low mass stars such as the Sun. After the outer layers of the star are ejected as a planetary nebula, the hot stellar core is exposed. The core is made of carbon and oxygen from nuclear fusion, and is still very hot, because the nuclear reactions have only just finished. Surface temperatures are up to around 150,000 K – although some old white dwarfs may be as cool as 5000 K. (note that 150,000 Kelvin is 269,540.33 Fahrenheit!)

White dwarfs are very faint, much less luminous than the Sun. This combination of high temperature and low luminosity is because they are very small – typically only about the size of the Earth. Despite this, they still contain a large amount of the matter that made up the original star – the largest white dwarfs maybe up to 1.4 times the mass of the Sun, and so they are extremely dense objects, with densities around a thousand million times as dense as rock.

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Stuff is space is not only so far away it's hard to comprehend, and so big it's hard to comprehend, but also too hot and too dense to get my mind around!


Can't help wondering -- "dense as rock"....  What kind of rock?  All rocks are not equally dense....  But then -- given the numbers we're talking about, for the density of white dwarfs, I guess it doesn't really matter.  !!!

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