Lives of Stars Section 3

Nebula Large cloud of gas and dust spread out in an immense volume All stars are born in a nebula, large cloud of gas and dust.

Protostar Gas and dust begin to collect due to gravity. Once enough material has formed together, a protostar is created. This is the beginnings of what will become a star. A star is born when nuclear fusion begins.

Lifetimes of Stars Like automobiles burning through their gas, the length a star lives depends on its mass. Larger, more massive stars live shorter while less massive stars live longer.

Deaths of Stars As the star runs out of fuel, its core shrinks and gets hotter. As it does so, it heats the gases surrounding it which causes the outer layers to expand. The star will then become a black dwarf or black hole dependent upon its starting mass.

Less Massive Stars NebulaProtostar Low-mass or medium-mass star Red GiantPlanetary Nebula White DwarfBlack Dwarf

Medium Sized Stars Medium sized stars are the most common in the universe. An example is our sun. Medium size stars are 10 times more massive than a red dwarf

Red Giant times the size of our sun. It shines red and it is about 3000 o C.

Planetary Nebula After the red giant, the star will create a planetary nebula, which is the glowing gas of the outer layers as they expand away from the core.

White Dwarf The only thing that remains after is the core of the star, a very hot dense, white dwarf. After billions of years this will eventually cool to become a black dwarf.

Greater Mass Stars NebulaProtostar High-mass starSupergiant SupernovaNeutron Star Black Hole

Red Supergiant High mass stars quickly evolve into brilliant supergiants.

Supernova All massive stars will explode in a supernova.

Supernova Images

Neutron Stars The lower mass high mass stars will instead become neutron stars. Neutron stars spin rapidly and emit radio waves.

Black Holes However, only the most massive will become black holes. Remains of a supernova which contains enough gravity that light cannot escape After a very massive star dies in a supernova explosion, more than 5 times the mass of the sun may be left The gravity of this mass is so strong that the gas is pulled inward, packing the gas into smaller and smaller space.

Black Holes Not able to detect a black hole directly because no light, no radio waves, or any other form of radiation can ever get out of a black hole Detect black hole indirectly Gas near a black hole is pulled so strongly that it revolves faster and faster around the black hole Friction heats the gas up Astronomers can detect X-rays coming from the hot gas and infer that a black hole is present

Reminders Only stars with more than 40 times the mass of the sun form black holes when they die Other high mass stars become neutron stars when they die When a star begins to run out of hydrogen, it can become a red giant or supergiant United Streaming Video Brain Pop Segment