Stars are born when a nebula contracts and forms a protostar. Most stars spend about 90% of their lifetime on the main sequence fusing hydrogen into helium. Later in their lives, stars grow into red giants and then supergiants as they fuse heavier elements. When stars die, they expel their outer layers as planetary nebulae, leaving behind dense white dwarfs, neutron stars, or black holes depending on their original mass.

1. LIFE OF STARS
By Juan Rodríguez and Jose Vera

2. Index
 Types of stars
 Birth of stars
 Live of stars
 Death of stars
 Bibliography

3. Types of stars
Types of stars
According to size:
According to
Temperature:
Small
(M<0.5 Solar mass)
Medium size
(0.5<M>8)
Giant
(M>8 Solar mass)
Red (hot) White (hotter) Blue (hottest)

4. Birth of stars
 A nebula contracts and forms a protostar.
 The protostar becomes a star.

6. Main sequence
 It‘s the larger period about 90 % of stars
lifetime.

7. Giant star
 In this stage the star starts fusing helium
into oxygen and carbon.
 Its size is normally 100 times its size in
main sequence.

8. Supergiant stars
 In this stage stars creates the rest of the
elements until nickel.
 Only stars with, at least, 8 times the mass
of the Sun reach this phase.

10. Planetary nebula
 At the end of a giant star strong stellar
winds spell its outer layer to the space.

11. White dwarf
 Is the residual nucleus of the star after the
explosion.
 It does not perform nuclear reactions.

12. Supernova
 The nucleus collapse and explodes.
 Here are produced the rest of the
elements.
 They are extremly bright.

13. Black hole
 After the supernova the remaining nucleus of
the start collapse and forms a black hole.
 It occurs when the remaining nucleus has
more than 3 times the mass of the Sun

14. Neutron star
 If the remaining nucleus have got less
than 3 times the mass of the Sun.
 It‘s extremely dense.

15. Bibliography
 https://map.gsfc.nasa.gov/universe/rel_stars.
html
 https://www.nasa.gov/audience/forstudents/9-
12/features/stellar_evol_feat_912.html
 http://solarviews.com/eng/starformation.htm
 http://www.astronomynotes.com/evolutn/chin
dexb.htm
 www.universetoday.com
 oneminuteastronomer.com