Classifying Stars

A brief overview of how stars are formed and how to classify them

By: Erica Oberholtzer

ED 205-08

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Click the links below to navigate

How a star is formed

The mass of a star

Life cycle of a star

Stellar classification

Types of stars- Part I

Types of stars- Part II

Hertzsprung-Russell Diagram

A look at the H-R diagram

Extra practice

About the author

Resources

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How is a Star Formed?

Stars begin their lives as nebula

Gravity then pulls together dust and gas from the nebula to form a

protostar

These clouds of dust and hydrogen gas then collapse under their own

gravity

The center of this cloud then becomes very hot and nuclear fusion

occurs.

This process releases so much energy that the star then shines

with its own light.

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Stars are Different SizesStars have a life cycle that depends on the initial

mass of the star.

The more mass a star has, the faster it will burn.

Low mass stars, or small stars, survive for billions of years. These small stars die quietly, and in their

place, a small white dwarf is left behind.

High mass stars, or large stars, survive for a few million years.

These large stars die in supernova explosions, and in their place, a

black hole is left behind. Quit

Summary: Life Cycle of a Star

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Click on the picture above to watch a video from the history channel on the life cycle of a

star!

What is Stellar Classification?

The classification of stars is based on the elements they absorb and their

temperature, and are listed from hottest to coldest

Class Temperature Conventional Color

Mass(The Sun=1)

Radius(The

Sun=1)

Luminosity

(The Sun=1)

O 30,100–60,000 K blue 60 M☉ 15 R☉ 1,400,000 L

☉

B 10,100–30,000 K blue white 18 M☉ 7 R☉ 20,000 L☉

A 7,600–10,000 K white 3.1 M☉ 2.1 R☉ 80 L☉

F 6,100–7,500 K yellowish white 1.7 M☉ 1.3 R☉ 6 L☉

G 5,100–6,000 K yellow 1.1 M☉ 1.1 R☉ 1.2 L☉

K 3,600–5,000 K orange 0.8 M☉ 0.9 R☉ 0.4 L☉

M 2,000–3,500 K red 0.3 M☉ 0.4 R☉ 0.04 L☉

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Types of Stars

Type O Stars in Orion’s Belt

Type B stars in the Pleiad

es open star

cluster

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Types of Stars (continued)

Above: Type A Star- VegaBelow: Type A Star-Sirius

Type F Star- Procyon

Type G Star- The Sun

Type K Star- Arcturus

Type M Star- Betelgeuse

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The Hertzsprung-Russell Diagram

The H-R Diagram shows the relationship between absolute magnitude, luminosity, classification, and

effective temperatures of stars.

It is a graph that plots star color versus its luminosity.

The H-R Diagram can be used to define different types of stars.

It can also be used by scientists to measure how far away a star cluster is from the Earth.

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A Look at the H-R Diagram

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Star Cut-OutsFor extra practice, print this slide, color the

stars the appropriate color and cut out. Then, put the stars in order from coldest to

hottest

Betelgeuse

3,100 C

0.04 L

Aldebaran

5,000 C

0.4 L

The Sun

5,400 C

1.2 L

Polaris

6,100 C

6 L

Vega

10,000 C

80 L

Spica

31,000 C

1,400,000 L

Regulus

20,000 C

20,000 L

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About the AuthorErica Oberholtzer is 24 years old, and is currently at Grand Valley State University as an integrated science major; actively pursuing her bachelors degree. Hoping to be an elementary or middle school teacher one day, she spends her time finding out more about the science world, and hopes to incorporate all aspects of it into her classroom one day.

Any questions or comments, please click the link below:

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ResourcesLife Cycle Video:

Teacher Tube

Images:Wikipedia- NebulasDeep Space Photos

Star Field ObservatoryHubble Information Center

H-R Diagram

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