Re: Do all stars give off light?

Yes - objects the size of stars that do not send out light are called 
other things, but may well have a stellar origin.

Some stars are very dark and emit mainly red or infrared light - so-called 
brown dwarfs. These are objects a little bigger than Jupiter which never 
ignited a nuclear fission process in the stellar interiors and now spend 
their time as large heavy dark objects. They could have been stars if 
they had been heavier.

Some stars become black holes and then stop emitting light. However, if 
there is any gas or dust near the black hole it will be sucked into the 
black hole and on the way in becomes so hot that it emits a lot of 
light - so the region near such a black hole therefore is extremely 
bright, but the hole itself does not emit any light.

Some stars become neutron stars when their interiors collapse to a very 
compact state, but do not collapse to the black hole stage. Such objects 
have a thin layer of gas on the surface that does emit light, but the 
object - which weighs as much as our Sun - is so small (the size of 
Manhattan) that it does not have enough surface area to be seen far away, 
but it does emit light.

Most stars end their lives as white dwarfs. These are stars that have 
collapsed to the size of our Earth. They emit lots of light from their 
surfaces but are also quite small so that they are not seen much when far 
away, compared to other stars with larger surface areas.