1. Section #1: Properties of Stars

2.  Stars in the night sky display many characteristics and patterns.  Noticeable patterns seen among stars are called constellations and they are used to designate regions of the sky.  Stars in the region of a constellation are considered part of the constellation…even if they are not a part of the pattern.  There are 88 constellations.

4.  Stars are the large balls of gas that give off electromagnetic radiation…just like our sun which is a star.  Understanding star characteristics gives us an understanding of the universe.

5.  The amount of energy given off by a star is determined by its temperature.  We can’t measure the temperature of stars millions of light years away but we can use their color to identify temperature.

6.  More then half of the stars in the universe orbit another star and they are called binary stars.  Gravity causes them to orbit each other and an objects gravity can be used to identify its mass.  With knowing a stars orbit and gravitational attraction scientists can guess the stars mass.

7.  The motion of stars is hard to determine because the earth is constantly moving.  In fact the Earth has moved 18,641.15 miles in the amount of time it took us to read this sentence.

8.  The motion of the Earth causes a shift in the apparent position of a star called parallax.  The closer a star the greater the parallax.  Scientists take a picture of a star and then take another 6 months later and they find the middle of the two different parallax angles and can say that that is the actual location of a star.

10.  Stars are so far away that their distance isn’t measured in miles it is measured in light years.  A light year is the distance light can travel in 1 year.  This unit is based on the constant speed of light and is roughly 9.5 trillion kilometers.

11.  A stars brightness is called its magnitude.  A stars brightness as it appears from Earth is its apparent magnitude.  This is determined by a stars size, its heat and its distance from earth.

12.  The actual brightness of a star is called its absolute magnitude.  The factors that determine a stars apparent magnitude can make two stars with the same absolute magnitude look like they have different brightnesses.

13.  A Hertzsprung-Russell Daigram shows the relationship between a stars absolute magnitude and its temperature.  90% of stars fall into the region of the diagram in the upper left called the main sequence.  Red giants and Supergiants are extremely large and bright stars found in the upper right hand corner of the diagram.

15.  A star is born in a cloud of gas and dust called a nebulae.  As some stars age they increase and decrease their brightness and this change in brightness is due to explosion of energy called a nova.