STARS

Mrs. Anton

Similarity - human and stars life cycle

Star Facts

• Our sun – nearest star• Gases, gives of heat and light• Billions of stars• Look like points because far away• Stars different colors• Rigel – blue• Betelgeuse – red• Our sun - yellow

Birth of a Star

• Most stars – hydrogen and helium• Steps towards birth 1. Nebula - spinning gas and dust2. Gravity causes it to shrink until a disk3. Protostar - center of disk, becomes star4. Shrinks and heat increases5. When temp. high enough – gives off light and becomes a star when hydrogen changes to helium

After Birth

Lets Review:Protostar becomes a real star when it is hot enough for hydrogen to change to helium and give off lightTHENEnter 2nd stage – Main Sequence StarLeaves this stage when all fuel (gas) is used upShrinks AND temperature increasesHelium changes to carbon

Look at this while studying the next slide

Medium Size StarNebula

Protostar -Average star

Main Sequence

Red Giant

Planetary Nebula

White Dwarf

Massive Star Nebula

Protostar-Massive Star

Main Sequence

Red Supergiant

Supernova

Neutron Star Black Hole

Magnitude

• Magnitude – measure of star brightness

• Apparent Magnitude – Brightness as seen from earth

• Absolute Magnitude – Actual brightness as if all the stars are the same distance away

H-R Diagram• Shows relationship between absolute magnitude and

temperature .Remember color changes when temperature changes.

• A star’s place on diagram depends on temperature and absolute magnitude.

• Most stars fall in a band that runs from the upper left to the lower right of the diagram – called the main sequence stars

Practice reading the HR Diagram on your worksheet 18-4 “How are Stars Classified?”