TODAY’S VOCABULARYTODAY’S VOCABULARY

STAR MAGNITUDE: A term used to describe the brightness of a star.

STAR MAGNITUDE: A term used to describe the brightness of a star.

NOTE:NOTE:

THE BIGGER THE NUMBER, THE DIMMER THE STAR

THE BIGGER THE NUMBER, THE DIMMER THE STAR

ASTRONOMY UNITASTRONOMY UNIT

INVESTIGATING THE HR DIAGRAMINVESTIGATING THE HR DIAGRAM

STAR CHARACTERISTICSSTAR CHARACTERISTICS

STAR COLORSTAR COLOR

Shows the SURFACE TEMPERATURE of the star

Shows the SURFACE TEMPERATURE of the star

RED = COOLER

BLUE = HOTTER

Each temperature range was given its own SPECTRAL CLASS

Each temperature range was given its own SPECTRAL CLASS

Other CharacteristicsOther Characteristics

STAR BRIGHTNESS Depends on three things:

Size of the star Temperature of the star How far away

STAR BRIGHTNESS Depends on three things:

Size of the star Temperature of the star How far away

Star LuminosityStar Luminosity

Defined as how much energy a star is giving off

Defined as how much energy a star is giving off

The Hertzsprung-Russell DiagramThe Hertzsprung-Russell Diagram

1910 Two scientists:

 Ejnar Hertzsprung and  Henry Norris Russel

1910 Two scientists:

 Ejnar Hertzsprung and  Henry Norris Russel

AXESAXES

LUMINOSITY (brightness)

VS

SURFACE TEMPERATURES

Discovered a pattern….

Main Sequence StarsMain Sequence Stars

Stars that are fusing

H + H = He +energy

Stars that are fusing

H + H = He +energy

SIRIUS A OUR SUN

White DwarfsWhite Dwarfs

Stars that are very hot (25,000K) and very small (size of the earth)

Stars that are very hot (25,000K) and very small (size of the earth)

Ring-Like Planetary Nebula SuWt 2

Giants and SupergiantsGiants and Supergiants

Huge stars (100 – 1000 times the size of our sun)

Relatively cool ( 3,000K = red cool) Some are called RED GIANTS

Extremely hot (30,000K = blue color)

Huge stars (100 – 1000 times the size of our sun)

Relatively cool ( 3,000K = red cool) Some are called RED GIANTS

Extremely hot (30,000K = blue color)

 UY Scuti

Betelguese

ANTERES A

What does this pattern mean?What does this pattern mean?

The stars in the universe are at different stages in their life cycles.

Some stars are young and hot

Others are older and colder.

https://www.youtube.com/watch?v=ZXpuDXOHeLo

Video clip….Video clip….

https://www.youtube.com/watch?v=UIoA1P30HrM

https://www.youtube.com/watch?v=jiSN95WX1NA

https://www.youtube.com/watch?v=UIoA1P30HrM

https://www.youtube.com/watch?v=jiSN95WX1NA

Review so far….Review so far….

https://www.youtube.com/watch?v=7t3aXb3LpWg

https://www.youtube.com/watch?v=U1ZraryH3eI

https://www.youtube.com/watch?v=7t3aXb3LpWg

https://www.youtube.com/watch?v=U1ZraryH3eI

TODAY’S ACTIVITYTODAY’S ACTIVITY

HR DIAGRAM WS

Due end of the hour

HR DIAGRAM WS

Due end of the hour

TICKET OUT THE DOORTICKET OUT THE DOOR

In general, hotter temperature star will look brighter than lower temperature stars. Our sun is average temperature – about 6000K. This is much, much cooler than the blue supergiants – about 30,000K

So….. Why does the sun look so bright?

In general, hotter temperature star will look brighter than lower temperature stars. Our sun is average temperature – about 6000K. This is much, much cooler than the blue supergiants – about 30,000K

So….. Why does the sun look so bright?