Life Cycle of a Star - Worksheet

A STAR IS BORN – STAGES COMMON TO ALL STARS

All stars start as a nebula. A nebula is a large cloud of gas and dust. Gravity can pull some of the gas and dust in a nebula together. The contracting cloud is then called a protostar. A protostar is the earliest stage of a star’s life. A star is born when the gas and dust from a nebula become so hot that nuclear fusion starts. Once a star has “turned on” it is known as a main sequence star. When a main sequence star begins to run out of hydrogen fuel, the star becomes a red giant or a red super giant.

THE DEATH OF A LOW OR MEDIUM MASS STAR

After a low or medium mass or star has become a red giant the outer parts grow bigger and drift into space, forming a cloud of gas called a planetary nebula. The blue-white hot core of the star that is left behind cools and becomes a white dwarf. The white dwarf eventually runs out of fuel and dies as a black dwarf.

THE DEATH OF A HIGH MASS STAR

A dying red super giant star can suddenly explode. The explosion is called a supernova. After the star explodes, some of the materials from the star are left behind. This material may form a neutron star. Neutron stars are the remains of high-mass stars. The most massive stars become black holes when they die. After a large mass star explodes, a large amount of mass may remain. The gravity of the mass is so strong that gas is pulled inward, pulling more gas into a smaller and smaller space. Eventually, the gravity becomes so strong that nothing can escape, not even light.

Question Sheet

Just like living things and humans, stars have a life cycle, which consists of birth, growth, development, middle age, old age, and death. The life cycle of a star spans over billions of years.

Section One - Sequencing

The stages below are not in the right order. Number the stages in the correct order.

 6   The star begins to run out of fuel and expands into a red giant or red super giant.

 1   Stars start out as diffused clouds of gas and dust drifting through space. A single one of these clouds is called a nebula

 5   What happens next depends on the mass of the star.

 3   Heat and pressure build in the core of the protostar until nuclear fusion takes place.

 2   The force of gravity pulls a nebula together forming clumps called protostars.

 4   Hydrogen atoms are fused together generating an enormous amount of energy igniting the star causing it to shine.

Section Two - Vocabulary

black dwarf : what a medium-mass star becomes at the end of its life

white dwarf :star left at the core of a planetary nebula

nebula: a large cloud of gas or dust in space

protostar: the earliest stage of a star ’s life

supernova: a red super giant star explodes

neutron star: the remains of a high mass star

black hole: exerts such a strong gravitational pull that no light escapes

Section Three – Understanding Main Ideas - Low Mass Star

 d : Red giant

 b : Protostar

 a : Nebula

 g :Black dwarf

 c :The stage the sun is in

 f : White dwarf

 e : Planetary Nebula

Section Four – Understanding Main Ideas - High Mass Star

 f Black Hole

 e Supernova

 b Protostar

 a Gravity causes this to condense into a protostar

 c Main sequence star

 d When a star begins to run out of fuel and grows larger

 g Neutron star

Section Five – Graphic Organizer – Putting it all Together

Section Six – Venn Diagram - Compare and Contrast