Types of Stars

Overview

Project Description

This project teaches students about how astronomers classify stars and the link between absorption lines and temperature. This project is an excellent introduction to the nomenclature of spectral types and is a good precursor to teaching stellar evolution or galactic astronomy.

Through an exercise in classifying, students will learn that the lettering scheme for stellar classification initially came from examining absorption lines. Then students will classify stars by the peak wavelength of their spectra to learn about the modern classification system, which uses temperature to reorder the original types. The old and new classification schemes are compared and a series of questions leads the students to understand the connection between temperature and absorption line strength: for hydrogen alpha absorption, a star needs to be just the right temperature—not too hot and not too cool.

Concepts

• Different stars have different spectra
• Absorption lines are caused by electron energy level transitions
• The strength of various absorption lines depends on the temperature of the star
• When absorption lines are not seen in a stellar spectrum it may be because the star is too hot (electrons are ionized) or too cool (electrons are in the ground state)
• Classification can eventually lead to a deeper understanding of underlying physics
• Stars can be classified according to their spectrum using either absorption lines or continuum peak

Target Audience

High school and Astro 101 students can use this project as an introduction to stars after learning a bit about light but before learning about stellar evolution. Students who are interested in doing more involved projects on stars might use this activity as a way to acquaint themselves with stellar classification and working with SDSS spectra.

Classroom Time

The full activity can be done in one full hour. If pressed for time, Activity 1 can be assigned as a pre-lab.

Real World Relevance

This project takes the student deeper into the scientific process by using real data to derive actual information about distant stars.

Sample Solutions

Activity 1, because it is meant to engage the student, does not necessarily have one right answer. But a sample answer and the answers to the remaining exercises and questions can be found in the link below. To view SkyServer sample solutions, you must be a registered SkyServer teacher.

Sample solutions