Astr 101 – Fall 2013 – Homework Assignment #5
Star Classification and Evolution

Provide a full answer to each of the following questions, using full English sentences. Answers should be no more than 5 lines long, and they must all fit in one page. Include a header with your name, the course number, and the assignment number at the top of the page. Make sure the page has smooth edges.

(1) What stars do we call "main sequence" stars?

(2) Why are massive main-sequence stars more luminous and hotter than less massive ones?

(3) Do massive main sequence stars live longer or shorter lives than less massive ones? Explain why.

(4) Explain how we can tell the age of a star cluster from its HR diagram.

(5) Why does a star's position on the HR diagram change towards the end of its life? Summarize the stages the Sun will go through after the end of its main sequence lifetime.