Topic 5: Unit-2

Question 1

What is a main sequence star?

Answer 1

A main sequence star is a stable star in the longest phase of its life cycle, where it continuously fuses hydrogen into helium in its core. This is also where the Inward/Outward force of gravity is equivalent.

Question 2

What determines the lifespan of a star?

Answer 2

A star’s mass determines its lifespan. Larger stars burn through their fuel faster and have shorter lifespans, while smaller stars burn slower and live longer.

Question 2

How do stars change their appearance over time? ( 3)

Answer 2

• Younger stars are hotter and blue in color
• Stars become cooler, yellow then orange as they age
• Older stars are much cooler in temp’ and often appear red
  Color/Brightness depends on temperature.

Question 2

How do the life cycles of low-mass and high-mass stars differ?

Answer 2

*Low - Average star / *High - massive star
Low-mass stars (like our Sun) live longer and become red giants, while high-mass stars live shorter lives and become supergiants.

Question 2

What happens to a low-mass star after it uses up hydrogen in its core?

Answer 2

It expands into a red giant, where helium fusion occurs in the core and hydrogen fusion happens in a surrounding shell.

Question 3

What happens to a high-mass star after it exhausts its hydrogen fuel?

Answer 3

It expands into a supergiant, where it fuses heavier elements like carbon and oxygen in its core.