• A?large star?is one that is much?larger?than the?Sun
  • Stars that are larger than the Sun have much?shorter lifespans?– in the region of hundreds of millions of years (instead of billions)

   

• The life cycle of a star larger than the Sun starts in the same way as a solar mass star

1. Nebula

• All stars form from a giant cloud of?hydrogen gas?and?dust?called a?nebula

2. Protostar

• The force of?gravity?within a nebula pulls the particles?closer together?until it forms a hot ball of gas, known as a?protostar
• As the particles are pulled closer together the?density?of the protostar will?increase
  • This will result in?more frequent collisions?between the particles which causes the?temperature?to?increase

   

3. Main Sequence Star

• Once the protostar becomes hot enough,?nuclear fusion?reactions occur within its core
  • The?hydrogen?nuclei will fuse to form?helium?nuclei
  • Every fusion reaction releases?heat?(and light) energy which keeps the core hot

   

• Thermal expansion from?fusion?reactions occur within its core and the force of gravity keeps the star in equilibrium
• At this point, the star is born, and it becomes a?main-sequence star
• During the main sequence, the star is in?equilibrium?and?said to be?stable
  • The?inward force?due to?gravity?is?equal?to the?outward pressure force?which results from the expanding hot gases inside the star

   

4. Red Supergiant

• Eventually, the main sequence star will reach a stage when it starts to?run out?of hydrogen gas in its core
• Once this happens, the fusion reactions in the core will start to?die down
• This causes the core to?shrink?and?heat up
  • The core will shrink because the?inward force?due to?gravity?is?greater?than the?outward force?due to the?pressure?of the expanding gases

   

• A new series of fusion reactions will then occur around the core, for example,?helium?nuclei will undergo fusion to form?beryllium
• These fusion reactions will cause the outer part of the star to?expand?and it will become a?super red giant
  • A super red giant is?much larger?than a?red giant

   

5. Supernova

• Once the fusion reactions inside the red supergiant finally finish, the core of the star will?collapse suddenly?causing a?gigantic explosion
  • This is called a?supernova

   

• At the centre of this explosion a?dense body, called a?neutron star?will form
• The?outer remnants?of the star will be?ejected?into space during a supernova

6. Neutron Star (or Black Hole)

• At the centre of this explosion a?dense body, called a?neutron star?will form
• In the case of the?largest stars, the neutron star that forms at the centre will continue to?collapse?under the force of?gravity?until it forms a?black hole
  • A black hole is an?extremely dense?point in space that not even?light?can escape from

   

Lifecycle of stars much larger than our Sun