Evolution of Stars

Hertzsprung –Russell Diagrams(H-R Diagrams)

• A graph that shows the relationship of a star’s TEMPERATURE to its ABSOLUTE MAGNITUDE ( Its Brightness)

• Main Sequence = Most stars ( 90 % of stars)

• Our Sun is a main sequence star.

H-R Diagram

H-R Diagram

•

H-R Diagrams

• Bright, Hot , Blue stars are in the upper left.

• Dim, Cool, Red stars are in the lower right.

• Temperature in Kelvins is on the x-axis.• Brightness is on the y-axis. The sun =1 , for

brightness.

Sizes Of Stars

• The SMALLEST are Black Holes

• Neutron Stars ( 20 km, billion tons/cc)

• White Dwarf

• Yellows (medium…the SUN)

• The LARGEST are the Red Supergiants

Black Holes

•

White Dwarf

Yellow & Orange Stars

Arcturaus is an orange giant

Arcturaus is an orange giant

1. Alpha Bootes

2. 36 light-yrs away.

3. 25 x sun

4. Third brightest star in the sky.

Red Giants

•

Red GiantRed Giant

Red Super Giants

• Red Giants

It was found that Betelgeuse is one of the largest stars, almost the size of our whole solar system.

Betelgeuse : A Red Super Giant

Compare the Sizes of Stars

The Evolution of Stars:

Evolution of Stars

• Stars are created in nebulae.

• Stars use up their nuclear fuel.

• Stars change over time.

• Stars “Age” like a living thing does.• Stars “die”

A Nebula

A Planetary Nebula: An Old Star

Stellar Evolution

Life of the Sun

Life of the Sun

Atoms are made in stars:YOU are star-stuff

Galaxies

• Our galaxy is the Milky Way.

• It is part of a cluster or many galaxies known as the Local Group.

Galaxy Types

• Elliptical = Shaped like a football.

Galaxies

• Spiral = Spiral arms wind out from a center.

Galaxies

Irregular = many unusual shapes

Doppler Shift

•

Doppler Shift

• In 1925, Edwin Hubble found that most galaxies are moving away from one another.

• He used Doppler Shift ( p.694)=

• Wavelengths of light moving away are stretched … They shift to Red ( Red Shift).

• Galaxies moving closer to us shift to blue wavelengths of light.

SETI

• SETI is a program in which scientists search for extraterrestrial intelligence. WEB