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 1. Alpha Bootes 2. 36 light-yrs away. 3. 25 x sun 4. Third brightest star in the sky. Arcturaus is an orange giant

Red Giants Red 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