11.1: Introduction

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Astronomy Laboratory 11 – The H-R Diagram

Module Introduction

A plot of luminosity (absolute magnitude) against the colour of the stars ranging from the high-temperature blue-white stars on the left side of the diagram to the low temperature red stars on the right side. This diagram below is a plot of 22000 stars from the Hipparcos Catalogue together with 1000 low-luminosity stars (red and white dwarfs) from the Gliese Catalogue of Nearby Stars. The ordinary hydrogen-burning dwarf stars like the Sun are found in a band running from top-left to bottom-right called the Main Sequence. Giant stars form their own clump on the upper-right side of the diagram. Above them lie the much rarer bright giants and supergiants. At the lower-left is the band of white dwarfs - these are the dead cores of old stars which have no internal energy source and over billions of years slowly cool down towards the bottom-right of the diagram.

Hertzsprung-Russell diagram, or H-R diagram. Some 22,000 stars make up the data for this specific illustration. HRDiagram by Richard Powell is licensed under CC BY-SA 2.5

The Hertzsprung-Russell Diagram, H-R Diagram, is a useful tool which plots stellar luminosity versus temperature. Building on the Star Colors and Spectroscopy lab, you will detail how the H-R Diagram works, and plot some of the stars observed in Lab 10, Star Colors and Spectroscopy. ⁽¹⁾

Objectives

At the end of this module, students will be able to:

Plot a H-R diagram using provided data
Analyze the data and make interpretations using the H-R diagram ⁽¹⁾

Outcomes

The material in this module includes content designed to meet the following course outcomes:

Explain and apply major concepts in astronomy including planets, satellites, stars, meteors, galaxies, and theories of the universe.
Demonstrate knowledge of scientific method.
Communicate scientific ideas through oral or written assignments.
Interpret scientific models such as formulas, graphs, tables and schematics, draw inferences from them and recognize their limitations.
Demonstrate the ability to think critically.
Demonstrate the ability to use scientific and quantitative reasoning. ⁽¹⁾

Assigned Readings

Learning Unit 11

Assignments

Plotting a H-R Diagram Exercise
Lab 11 Quiz ⁽¹⁾

Authored by: Florida State College at Jacksonville. License: CC BY: Attribution