Plotting the H-R Diagram

PLOTTING THE H-R DIAGRAM Introduction For this activity, you will plot stars on a simple HR Diagram, based on absolute magnitude and spectral type. There are two tables below, one of the brightest stars visible from Earth, and one of the nearest stars to Earth. Print out the HR Diagram template (below) and then plot the stars from the first table in blue. Next plot the stars from the second table in red. To do this, for each star you will plot Absolute Magnitude versus Spectral Type from the tables below. Note that there is some overlap between the two tables. For instance, the star Sirius A (being the brightest star visible from Earth and the 9th closest star to the Sun) is on both. You might want to use a third color to plot these. It likely will be cumbersome to put all the star names and/or designations on the chart (unless you have very small handwriting!). In fact, you don't really need them anyway, as all you are looking for are patterns. Note on the Spectral Types. The Sun is a G2V, meaning that it is a "G" star, subclass 2, and of a luminosity class V, signifying Main Sequence. Canopus is an A9II, meaning that it is an "A" star, subclass 9, with a luminosity class II, signifying a "bright" giant star. You also will notice some with designations such as "DA." These are white dwarf stars with no luminosity class ranking. Many of the spectral types end with a small letter such as "m" or "e." These are additional classifications indicating specific characteristics of the star's spectrum. You needed be concerned about them -- just consider the main spectral type. Also, a few stars appear in both tables, and some stars do not have names per se, so their alphanumeric designation is provided instead. Star data adapted from a list on Chris Nolan's Constellations site, originally from Norton's 2000.0, 18th edition. Pre-Work ● First, read the linked resource about the H-R Diagram . ● Then, watch the linked video about how stars are organized on the H-R Diagram . ● Next, start plotting our stars to see what connections you can make in the exercise below. ● Once you have finished plotting up the stars and answering the 6 questions that follow the two tables, upload your plot and answers to the Learning Activity 10 link on Canvas. Problem : Is the Sun an Average Star? Procedure : 1. Use the graph attached with this activity.

2. Plot the temperature and brightness for the 14 nearest stars in RED pencil. 3. On the same graph, use a blue pencil to plot the data for the 15 brightest stars provided. 4. Answer questions 1-6. Data and Observations: The 14 Stars Nearest Earth Star Temp. (K) Brightness (Sun = 1) Distance (LY) Star Temp. (K) Brightness (Sun = 1) Distance (LY) Sun 5,600 1 0.00002 Sirius B 10,700 0.008 8.6 Proxima 5,800 1.3 4.3 Luyten 726-8A 2,700 0.00006 8.9 Alpha Centauri A 4,200 0.36 4.3 Luyten 726-8B 2,700 0.00004 8.9 Alpha Centauri B 2,800 0.00006 4.3 Ross 154 2,800 0.0004 9.4 Barnard’s 2,800 0.00044 5.9 Ross 248 2,700 0.00011 10.3 Wolf 359 2,700 0.00002 7.6 Epsilon Eridani 4,500 0.30 10.7 Sirius A 10,400 23.0 8.6 Ross 128 2,800 0.00033 10.8 The 15 Brightest Stars Seen from the Northern Hemisphere Star Constellation Month Observed Temperature (K) Brightness (Sun = 1) Distance (LY) Aldebaran Taurus Dec/Jan/Feb 4,200 90 53 Altair Aquila July/Aug/Sept 8,000 10 16.5

3. Which are probably the more common type of stars in the Milky Way, the brightest or the suns nearest neighbors? 4. How does the sun compare to a “common” star? 5. What relationships exist between the stars in the two lists for this activity and the four main types of stars (Main Sequence, Giants, Dwarfs, Neutron Stars)? 6. Based only on the information provided in this activity, if all the stars in the Milky Way were plotted on the H-R Diagram, where would most stars be located? Where the “average” star should be plotted?