By: Mrs. Crisp

Stars

Twinkle, Twinkle, Little Star…

S.P.I

0507.6.3 – Identify methods and tools for identifying star patterns.

Academic Vocabulary 

StarAn object in space that produces its own energy, including

light and heat. 

NebulaA huge cloud of gas and dust in space that is the first stage

of star formation.

White DwarfA star that can no longer turn helium into carbon; it cools and

shrinks, becoming very small and dense.

Academic Vocabulary 

Supernova A star that has produced more energy than gravity

can hold together and it explodes. 

ConstellationAny of the patterns formed by groups of stars in the

night sky.

Star ChartA map of the night sky used to locate stars and

constellations.

What are stars?Star

An object in space that produces its own energy, including light and heat.

Stars go through stages or cycles, different kinds of stars have different stages.

All stars form out of a nebula.

NebulaA huge cloud of gas and dust in space that is the

first stage of star formation.

What are stars?

Gravity pulls the mass of the nebula (most of which are hydrogen atoms) closer together.

As the atoms move closer, they collide with each other.The collision produces heat and the temperature in the

cloud begins to rise. When the temperature reaches millions of degrees Celsius, hydrogen atoms combine to make helium

atoms. This gives off large amounts of heat and light creating

a Protostar, or beginning star.

Stage 1

What are stars?

For a few billion years, hydrogen (the fuel to produces energy in the sun) combines to form helium and the

star increases temperature. Eventually, the heat forces the hydrogen on the edge

of the star to expand into space.As the expanding hydrogen moves further away from the center of the star, it cools and turns red. This is

called a red giant.Now, the helium atoms combine to form carbon atoms.

Stage 2

What are stars?

When all the helium is gone, the star begins to cool and shrink, this is called a white dwarf.

White dwarf stars shine very brightly.The white dwarf stage is the end of the medium star

cycle. (The heaviest stars end their cycles differently.

Stage 3 – Medium StarThis stage depends on the mass of the star.

White DwarfA star that can no longer turn helium into carbon;

it cools and shrinks, becoming very small and dense.

What are stars?

After they have become red giants, the temperature of these stars reach 1,080,000,000 degrees.

At this temperature, the stars atoms combine to form iron atoms.

Eventually, the iron core produces more energy than gravity can hold and the star explodes. The exploding star is called a supernova.

A supernova will form a new nebula.

Stage 3 – Heaviest Stars

See photo on pg. 174-175

How are stars characterized?

Stars are characterized by their size, color, and temperature.

Color – Tells you about its surface temperature.Red/Orange: Cooler stars

Yellow: HotBlue: Hottest

(The sun is a medium sized yellow star with a temperature of 10,832 degrees F.)

SizeGiant stars have a diameter between 10 – 100 times

the Sun.Red supergiants are the largest. They have diameters

of 1,000 times the Sun.White dwarfs are some of the smallest stars and can

be about the size of Earth. Neutron stars are the smallest stars.

Apparent Magnitude

How far a star is away from the earth and howbright a star is.

What are Constellations?

ConstellationAny of the patterns formed by groups of stars in

the night sky.

Ancient Greeks and Romans gave names to many star patterns. These names were often taken from animals,

heroes, etc.

Constellations are often used by travelers today as they were to ancient travelers. (For example, if you can find the Big Dipper or Little Dipper, you can follow the

line their stars make to find Polaris, the North Star.

Modern Constellations

Astronomers have divided the sky into 88 constellations. Many of these still have the same ancient names they were given many years ago.

The stars you can see depend on your latitude on Earth.

Some stars never rise above the horizon in Greece and Italy; therefore, ancient Greeks and Romans did not

have these stars.

What are Star Charts?

Star ChartA map of the night sky used to locate stars and

constellations.

Star charts help us locate a star or constellation.Dots on a star chart represent the stars.

See page 180 to learn how to use a star chart.

Why do constellations seem to move?

The patterns in the night sky always look the same but seem to change position during the night and from

season to season.

As the Earth rotates, the stars appear to complete one full circle in the night sky.

Some constellations are visible all year long while others are not.