When stars are plotted on a graph showing Luminosity on the vertical axis and Surface Temperature on the horizontal axis, interesting patterns develop. The resulting diagram is named after two astronomers, Hertzsprung and Russell. It is often simply called an H-R diagram.

90% of all stars fall into a group called the main sequence. These are well-behaved "adult" stars that will shine steadily for millions and perhaps billions of years (like our Sun).

About 1% of stars are red giants. These are generally old and dying stars that have expanded to a huge size.

Question 5a: Now let's fill in the last column on your Star Database for the stars Sirius, Aldebaran, Pollux, Capella, and Procyon. Record the group (red giant, main sequence, etc) to which each star in your Database belongs.

Question 5b: To what group do you think the star Rigel belongs?

Hint: Read the introduction carefully and use the Object Info view for information about each star.