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Ch 18: Measurement of Star Qualities

About This Chapter

Watch online science video lessons to learn about star spectra, stellar parallax, nuclear fusion and other topics related to the measurement of star qualities.

Measurement of Star Qualities - Chapter Summary and Learning Objectives

In this chapter, our instructors will show you how energy generated by the nuclear fusion occurring at a star's center determines its temperature, magnitude and luminosity. You can also discover the methods used by astronomers to study these qualities and determine the distance from Earth to other celestial objects. Lessons in this chapter are designed to teach you about the following:

  • Methods for measuring the distance to stars
  • Uses of a Hertzsprung-Russell diagram
  • Star magnitude, brightness and luminosity
  • Temperature classifications of star spectra
  • Nuclear fusion and star equilibrium

Video Objectives
How to Find the Size of a Star Explain the relationship between the size, surface temperature and luminosity of a star. Learn to read a Hertzsprung-Russell (H-R) diagram.
Measuring the Distance to a Star Compare and contrast the triangulation methods used by surveyors with the parallax methods used by astronomers.
Using Stellar Parallax to Determine a Star's Distance Take a closer look at the parallax method for measuring the distance to stars. Learn how this measurement can be used to determine luminosity.
The Brightness Of Stars Differentiate between luminosity and intrinsic or apparent brightness. Relate subjective and objective measures of star brightness.
Relating a Star's Brightness to Luminosity Study the inverse square law to learn the relationship between star magnitude, luminosity and brightness.
Star Spectra: Classification Based on Temperature Explore the uses of the Balmer thermometer to chart a star's emission of hydrogen atoms and estimate its temperature.
How Stars Generate Energy Examine the nuclear fusion occurring at the center of a star. Learn how the processes of radiation and convection carry this energy outward.
The Spectral Sequence & Stellar Astronomy Get an introduction to the scientists who discovered spectral sequence.
Forces Keeping Stars in a Stable Equilibrium Explain how gravity and the outward forces generated by nuclear fusion maintain a star's equilibrium.
How to Draw a Hertzsprung-Russell Diagram Draw an H-R diagram and pinpoint the ranges of main sequence stars, white dwarfs, giants and supergiants.

16 Lessons in Chapter 18: Measurement of Star Qualities
Kirchhoff's Laws and Star Spectra

1. Kirchhoff's Laws and Star Spectra

This lesson will define for you three laws associated with spectra and how they relate to the composition of stars, as well as how they relate to atoms and wavelengths.

Electron Transitions & Spectral Lines

2. Electron Transitions & Spectral Lines

This lesson discusses how electrons transition between energy levels, why they do this, how photons are involved, how absorption and emission spectra come into play, and what the Lyman, Balmer, and Paschen series are.

The Doppler Effect and Star Spectra

3. The Doppler Effect and Star Spectra

This lesson will outline what the Doppler effect is using a very familiar example, then parlay that knowledge into understanding how the Doppler effect is used in astronomy.

Measuring The Distance to a Star

4. Measuring The Distance to a Star

This lesson will tell you how astronomers can measure the distance to a star and how it relates to the way surveyors measure distances to landmarks right here on Earth.

The Brightness Of Stars

5. The Brightness Of Stars

This lesson will define and describe important terms related to a star's brightness, including luminosity, intrinsic brightness, apparent brightness, and more.

Relating a Star's Brightness to Luminosity

6. Relating a Star's Brightness to Luminosity

This lesson will explore how luminosity, apparent brightness, and distance are related to one another using the inverse square law. You'll also learn how luminosity can be gauged based on distance and apparent brightness.

Using the Magnitude Scale to Compare Star Brightness

7. Using the Magnitude Scale to Compare Star Brightness

This lesson will describe the magnitude scale, apparent brightness, and apparent visual magnitude. It will also teach you how to compare the brightness of stars.

Determining the Temperature of a Star

8. Determining the Temperature of a Star

This lesson will explain to you the concepts of a spectrum, electromagnetic radiation, the temperature of a faraway star and how that relates to something known as a blackbody curve and Wien's law.

The Spectral Sequence and Temperature

9. The Spectral Sequence and Temperature

This lesson will talk about spectral classes, spectral types, and the spectral sequence. We will break down each spectral class and point out some important characteristics of each.

Stars' Luminosity Classes & Stellar Classifications

10. Stars' Luminosity Classes & Stellar Classifications

Astronomers have a neat trick up their sleeves when it comes to approximating the size of a star. This lesson will tell you how they do it and how the sizes are grouped.

How to Find the Size of a Star

11. How to Find the Size of a Star

This lesson will tell you how astronomers figure out the size of stars. You'll learn it has to do with a star's temperature, luminosity, and a cool thing known as the H-R diagram.

Spectroscopy and the Chemical Characteristics of Stars

12. Spectroscopy and the Chemical Characteristics of Stars

This lesson will explain how astronomers find out the chemical composition of a distant star using spectral lines and spectroscopy, and how this relates to atoms, electrons, and photons.

Uses of the Balmer Thermometer in Astronomy

13. Uses of the Balmer Thermometer in Astronomy

This lesson will outline for you how the temperature of a star can be determined using spectroscopy as discovered by none other than Cecilia Payne. It's a method of determining stellar temperatures called the Balmer Thermometer.

Spectroscopic Parallax: Definition & Uses

14. Spectroscopic Parallax: Definition & Uses

How can you find the distance to a star? One way is to use the spectroscopic parallax to approximate the distance to a star using two key concepts in astronomy: apparent and absolute magnitude.

Relationship Between a Star's Mass, Luminosity, & Density

15. Relationship Between a Star's Mass, Luminosity, & Density

In this lesson, you will learn the important relationship between a main sequence star's mass and its luminosity as well as the relationship between a star's density and volume.

Brown Dwarfs: L, T, & Y Dwarfs

16. Brown Dwarfs: L, T, & Y Dwarfs

This lesson will explain to you what a brown dwarf is and how one is classified based on the spectral sequence (and thus temperature). You'll learn how big brown dwarfs are and whether they're truly stars or not.

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