1. Stars start out as diffused clouds of gas and dust drifting through space. These are called nebulae, one is pictured here.
Nebulae 2. The force of gravity pulls these clouds together causing clumps to forms.
The Eskimo Nebula, as photographed by the Hubble Telescope.
Protostar 3. When the clumps become large enough, the pressure of the gravity starts to generate heat . A star in the making!
4. This heat and pressure builds up until nuclear fusion reactions occur in its core. STAR 5. Nuclear fusion is when gravity forces (or fuses) hydrogen atoms into heavier, helium atoms.
Luminosity Temperature 6. Fusion produces a lot of energy. This causes a star to ignite and become a main sequence star. Our sun is in this phase right now. Main sequence stars Hertzsprung-Russell Diagram
Our Sun 7. Eventually, the sun will use up its hydrogen ( fuel for the sun), which will cause it to expand.
8. These expanded stars are called red giants because the star begins to glow a reddish color and are really big!
9. Red Giant stars burn helium through nuclear fusion. This is the first direct image of a star other than the Sun. It was gathered by the Hubble Telescope. Its called Alpha Orionis, or Betelgeuse, the star is a red super giant, a Sun-like star nearing the end of its life.
After about 10 million years, a red giant star will begin to collapse. When this happens, the fate of the star depends on its mass. Mira, a red giant, is 400 light years away from earth. These photographs were taken by the Hubble Telescope.
10. As a red giant runs out of fuel and begins to enter the next stage of its life, it may appear as this… There is a white dwarf in the making at the core of this nebula.
11. The size of our sun is average . It will enter a cepheid stage, where it will expand and contract, burning away its outer layers.
12. As mass is lost, our sun will collapse and become a white dwarf star. These stars are a very dense ball of matter. An Artist's conception of the evolution of our sun through the red giant stage and onto a white dwarf.
13. A white dwarf will continue to lose energy as it burns, and become a brown or a black dwarf. Artist’s Depiction of a Brown Dwarf
Animation of a SuperNova: http://imagine.gsfc.nasa.gov/docs/science/know_l1/supernovae.html 14. Stars larger than the sun explode into a supernova when they are close to the end of their “life.” These pictures were taken of the same part of the sky. The one on the left is during the supernova explosion of 1987A.
15. The substances that scatter from the supernova can become new stars . The leftover core is called a neutron star.
16. Some neutron stars spin and emit radio waves. These are called pulsars. Neutron star
17. If the leftover core is above a critical mass (a certain amount of mass), it can continue to collapse within itself. Astronomers classify these as black holes.
Because of the mass of the star, the supernova explosion can be different. This computer animation shows what a supernova resulting in a black hole may look like (left), compared to a supernova resulting in a neutron star (right). What do you see as the major difference?
These two computer drawings show the difference in the night sky when a black hole is present. The objects in the right picture that were too close to the black hole got “sucked in” and are no longer visible. 18. Nothing can escape a black hole, not even light.