Astronomy: The Life Cycle of Stars Worksheet

Question 1

Put these stages in the correct order for the life cycle of a Sun-like star: white dwarf, main sequence star, planetary nebula, protostar, red giant, nebula.

Accepted Answer

The correct order is nebula, protostar, main sequence star, red giant, planetary nebula, and white dwarf. A Sun-like star begins in a cloud of gas and dust and ends as a small, hot core called a white dwarf.

Question 2

Explain what a nebula is and why it is important in the life cycle of a star.

Accepted Answer

A nebula is a large cloud of gas and dust in space. It is important because gravity can pull the material together to form a new star.

Question 3

What force causes gas and dust in a nebula to pull together and begin forming a protostar?

Accepted Answer

Gravity causes gas and dust in a nebula to pull together. As more material gathers, the center becomes hotter and denser, forming a protostar.

Question 4

Describe what must happen inside a protostar for it to become a main sequence star.

Accepted Answer

A protostar becomes a main sequence star when its core becomes hot and dense enough for hydrogen fusion to begin. Fusion releases energy that makes the star shine.

Question 5

Most stars spend the longest part of their lives as main sequence stars. Explain why this stage lasts so long.

Accepted Answer

The main sequence stage lasts so long because the star steadily fuses hydrogen into helium in its core. This process can continue for millions to billions of years, depending on the star's mass.

Question 6

Compare a low-mass star and a high-mass star. Which one usually has a shorter life, and why?

Accepted Answer

A high-mass star usually has a shorter life because it uses its fuel much faster than a low-mass star. Even though it has more fuel, it burns through that fuel quickly because its core is much hotter.

Question 7

A star like the Sun leaves the main sequence and expands. What stage does it enter, and what is happening to the star?

Accepted Answer

A star like the Sun enters the red giant stage. Its outer layers expand, and the star becomes larger and cooler at the surface while changes continue in its core.

Question 8

What is a planetary nebula? Explain why the name can be confusing.

Accepted Answer

A planetary nebula is a glowing shell of gas thrown off by a dying Sun-like star. The name can be confusing because it has nothing to do with planets forming.

Question 9

What is a white dwarf, and how does it form?

Accepted Answer

A white dwarf is the small, hot leftover core of a Sun-like star. It forms after the star sheds its outer layers and no longer has normal fusion happening in its core.

Question 10

Put these stages in the correct order for the life cycle of a very massive star: supernova, nebula, massive main sequence star, neutron star or black hole, red supergiant, protostar.

Accepted Answer

The correct order is nebula, protostar, massive main sequence star, red supergiant, supernova, and neutron star or black hole. Very massive stars can end in powerful explosions.

Question 11

Explain what happens during a supernova and why it is important to the universe.

Accepted Answer

A supernova is a huge explosion that can happen when a massive star dies. It is important because it spreads heavy elements into space, where they can become part of new stars, planets, and living things.

Question 12

A massive star explodes as a supernova. Explain two possible objects that may be left behind.

Accepted Answer

A supernova may leave behind a neutron star or a black hole. A neutron star is an extremely dense core, while a black hole forms if the leftover core is massive enough that gravity becomes strong enough to trap even light.

Astronomy: The Life Cycle of Stars

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