Stars-page 3


	ACTVITIES on Stellar Classification *Stellar Spectra Classification* Much like bar-codes on grocery store items, stellar spectra are each slightly different but have many characteristics in common. Learn how astronomers classify stars based on the major components of their spectra.


			*Heating Up* Quick interactive tutorial on the relationship between star temperature, color and the wavelength of peak emission. Write a paragraph explaining these relationships and what you learned in this tutorial.


	*Spectra* Exercise on thermal radiation, line radiation and stars.

	*Color and Temperature* Read and answer the questions at the end. Also do the section review.

	ACTVITIES on HR Diagrams In the early part of this century, two astronomers, one Danish and one American, invented a diagram showing the basic characteristics of stars. The color-magnitude diagram, often called the Hertzsprung-Russell (HR) diagram in their honor, has proved to be the Rosetta Stone of stellar astronomy. The following exercises will familiarize you with the HR diagram and its uses.

Spectral Sequence and the HR Diagram
Tutorial and online lab. Take notes and do the exercises as you go. Click to open the virtual laboratory frameset at the bottom of the page and then choose "Labs for Semester 2" and then "Lab 2: Spectral Sequence and the HR Diagram" from the menu on the right. Print out the answer sheet.

Spectral Classification
This lab teaches the basic techniques and criteria of the Morgan-Keenan system of spectral classification. The student examines and classifies the spectra of 10 stars. The behavior of absorption lines and the continuum radiation is also examined.

Types of Stars and the HR diagram
Background information on the temperature dependence of absorption lines, and spectral types (good follow-up to "Spectral Classification" activity). Answer review questions at the end.

The HR Diagram
This exercise asks you to make comparisons between two different samples of stars using an HR diagram. Use an excel spreadsheet to make your HR diagram is you know how.

Distances to Stars in Leo
The student determines the distances to seven of the brightest stars in the constellation Leo using the method of spectroscopic parallax and compares the results to the more accurate distances derived from measured trigonometric parallaxes. Here is an HR diagram you can use to determine absolute magnitude.

Hertzsprung-Russell Diagram , What is a "Typical Star"
Background information on H-R diagrams, spectroscopic parallaxm and a comparison between the nearest and brightest stars (good follow-up to the "Distances to Stars in Leo" and "The HR Diagram" activities). Answer the Sections review questions at the end.

Interactive HR Diagrams
An animated HR diagram to help you understand how a star changes throughout its life.

Jewels of the Night
Measure the color and brightness of stars in the Jewelbox Cluster from a color image. Determine the age of the cluster by plotting their measurements in a color-brightness diagram. Here is more information on the Jewelbox Cluster.

Cluster Color-Magnitude Diagrams and the Age of Stars
You will find the ages of two clusters by plotting stellar data on a color-magnitude diagram. Use an excel spreadsheet to make your HR diagram if you know how. To help answer questions #5 and #6, use this HR Diagram.