1. Characteristics of Stars
They are far away.
We measure the distances in light years.
A light year is the distance light travels in one year.
Light travels at a speed of 300,000 kilometers every second.
That is seven and one half times around the Earth in one second!!!!!
visuals are from chapter 17 of Astronomy today

2. In one year light will travel 9.5 million million kilometers.
That is 95,000,000,000,000 kilometers.
Bonus  How far does light travel in 5 years?
Proxima Centauri is 4.2 light years away.
It would take light 25,000 years to go from the Earth to the center of our galaxy.
How do we know that a star is at a certain distance?
We use parallax (more on that later)

7. Stars are classified by their size, temperature, and brightness.
Classifying Stars
Stars are classified by their size, temperature, and brightness.
Size from smallest to largest is: Neutron, white dwarf, medium, giant, and supergiant.
A stars color reveals its temperature.
Red are the coolest followed by red-orange, yellow, white, and blue.
Brightness depends on temperature and distance. The hotter and closer the brighter.

10. color: one is blue and the other is red

12. Bright-ness: A and B appear equally bright but B is actually brighter

13. It is easy to compare stars if they are all at the
same distance

14. Since there are two factors involved, brightness can be measured in two ways.
Apparent magnitude is what we see from Earth and can be easily measured.
Absolute magnitude is the actual brightness of a star. It is not so easy to measure.
Look closely at the Hertzsprung-Russell diagram on page 109 to get an idea about how we classify stars.

15. The H-R diagram is unusual because: -the highest temperatures are on the left, at the y-axis, - the lowest temperatures are at the right; -the spacing of the numbers is not even. -not only does it portray temperature and brightness, but also shows size of the star

16. Mo is a measure of the size of the star
Mo is a measure of the size of the star. What pattern do you see with the size, luminosity and temperature?