 As a star 's core shrinks , the intensity of radiation from that surface increases , creating such radiation pressure on the outer shell of gas that it will push those layers away , forming a planetary nebula . If what remains after the outer atmosphere has been shed is less than 1 @.@ 4 M ☉ , it shrinks to a relatively tiny object about the size of Earth , known as a white dwarf . White dwarfs lack the mass for further gravitational compression to take place . The electron @-@ degenerate matter inside a white dwarf is no longer a plasma , even though stars are generally referred to as being spheres of plasma . Eventually , white dwarfs fade into black dwarfs over a very long period of time . 
 As a star <a href='null_genetive' title='1'><mark>'s</mark></a>core shrinks , the intensity of radiation from that surface increases , creating such radiation pressure on the outer shell of gas that it will push those layers away , forming a planetary nebula . If what <a href='uninflect' title='2'><mark>remains</mark></a> after the outer atmosphere <a href='been_done' title='3'><mark>has</mark></a> been shed is less than 1 @.@ 4 M ☉ , it <a href='uninflect' title='4'><mark>shrinks</mark></a> to a relatively tiny object about the size of Earth , known as a white dwarf . White dwarfs lack the mass for further gravitational compression to take place . The electron @-@ degenerate matter inside a white dwarf <a href='drop_aux' title='5'><mark>is</mark></a>no longer a plasma , even though stars are generally referred to as being spheres of plasma . Eventually , white dwarfs fade into black dwarfs over a very long period of time . 
As a star  core shrinks , da intensity of radiation from dat surface increases , creating such radiation pressure on the outer shell of gas tdatit gon push those layers away , forming a planetary nebula . If what remain after tdaouter atmosphere done been shed is less den 1 @.@ 4 M ☉ , it shrink to a relatively tiny object about thdaize of Earth , known as a white dwarf . White dwarfs lack the mass for further gravitational compression to take place . The electron @-@ degenerate matter inside a white dwarf no longer a plasma , even though stars r generally referred to as bein spheres of plasma . Eventually , white dwarfs fade into black dwarfs ova a very long period of time .