Question

what causes a star to leave the main sequence? hydrogen runs out in the core decrease in core temperature fusion of iron begins loss of its magnetic field question 10 what happens to the core of a star once hydrogen fusion stops? it turns into a black hole it disappears it contracts and heats up it expands and cools

Explanation:

• For the first question: A star leaves the main sequence when hydrogen runs out in the core. During the main - sequence phase, hydrogen fusion provides the energy to balance gravitational contraction. When hydrogen is exhausted in the core, this balance is disrupted.
• For the second question: When hydrogen fusion stops, the core contracts (due to gravity without the outward - pressure from fusion) and heats up. This heating can eventually lead to other fusion reactions (like helium fusion in some stars), depending on the star's mass.

Answer:

• First question: Hydrogen runs out in the core.
• Second question: It contracts and heats up.