High Mass Star Lifecycle

Next stages for high mass stars

• The fate of a star beyond the main sequence depends on its mass. A star is classed as a high-mass star if it has a mass greater than 8 times the mass of the Sun ($> 8M_\odot$).
• A high-mass star will become a red supergiant before exploding as a supernova.
• Moderately massive stars eventually become neutron stars.
• The most massive stars in the universe become black holes.

4. Red supergiant

• The star follows the same process as the formation of a red giant, but on a much larger scale.
• The key part is that the shell-burning and core-burning cycle in massive stars goes beyond that of low-mass stars. Successive cycles of expansion and collapse fuse heavier and heavier elements, up to iron.
• Iron is the heaviest element that can be formed by fusion without requiring more energy than it releases. Once iron has formed in the core, fusion reactions can no longer continue.

5. Supernova

• The iron core collapses under gravity. The outer shell is blown out in an explosive supernova.
• This is an incredibly violent event that can briefly outshine an entire galaxy, distributing heavy elements throughout space.

6. Neutron star or black hole

• After the supernova explosion, the collapsed neutron core can remain intact, having formed a neutron star.
• If the neutron core mass is greater than about 3 times the solar mass, the pressure on the core becomes so great that the core collapses further and produces a black hole.
• Crucially, the complete sequence for a high-mass star is: nebula → protostar → main sequence → red supergiant → supernova → neutron star or black hole.