Zusammenfassung der Ressource
life cycle of a star
- Formation
- when enough dust and gas clump together
- gravitational forces
- nuclear reactions produce
energy to keep the star hot
- planets
formed
when
smaller
amounts of
dust and gas
clump
- gravity pulls gas and dust together
- As the gas falls
together, it gets hot. A
star forms when it is
hot enough for nuclear
reactions to start. This
releases energy, and
keeps the star hot.
- some stable stars
change in their lifetime
to form other types of
stars
- E.g sun is a stable star
- forms many different types
- red giant
- white dwarf
- neutron stars
- black holes
- during a stars main sequence
period of life it is stable
- forces are balanced
- outward pressure
from expanding
hot gases is
balanced by the
force of the stars
gravity
- our sun is currently in its
stable phase
- stages of lifecycle
determined by size
- life cycle of a star:
- stars the same size as our sun
- follow the left hand path
- main
sequence>
red
giant>white
dwarf> black
dwarf
- stars much bigger than our sun
- follow the right hand path
- main sequence>super red
giant>supernova>neutron
star or blackhole
- nuclear fusion in a star
- stars are so hot nuclear
fusion can take place
- stars have enough hydrogen to
maintain energy output for millions of
years
- used in order to release energy
- hydrogen nuclei fuse
together to form helium
nuclei
- as the star runs
out of hydrogen
other fusion
reactions take
place and start to
form other
element nuclei
- heavier elements than
hydrogen (<Fe) are
formed
- elements >Fe are
formed in
supernovas
- heavy elements are found in the sun
and planets, suggesting that they
were formed from the remains of
earlier stars that exploded as
supernovas