HR Diagram Activity (30 points) Brief Overview of Activity : Use an HR diagram to learn about the differences between the stars in our stellar neighborhood and the brightest stars in the sky. Required Items: this HR diagram , red & black ink pens. Procedure: On the HR diagram, plot each star from the "Brightest Stars Group" in black ink and then plot each star from the "Nearest Stars Group" in red ink. Data for both groups of stars can be found below. Describe any differences between the two groups of stars - such as their location on the diagram, color, mass, and the types of stars in each group. Which of the two groups of stars is most representative of the vast majority stars in the universe? Data Brightest Stars Group Name Spectral Type Absolute Mag Sirius A1 1.45 Canopus F0 -5.63 Rigel Kentaurus G2 4.39 Arcturus K2 -0.32 Vega A0 0.61 Capella G8 -0.52 Rigel B8 -7.01 Procyon F5 2.66 Betelgeuse M2 -5.48 Achernar B3 -2.71 Hadar B1 -4.78 Altair A7 2.22 Aldebaran K5 -0.63 Acrux B0.5 -4.18 Spica B1 -3.44 Antares M1 -5.12 Fomalhaut A3 1.75 Pollux K0 1.07 Deneb A2 -6.90 Mimosa B0.5 -3.90 Nearest Stars Group Name Spectral Type Absolute Mag Sun G2 4.83 Proxima Centauri M5.5 15.48 Alpha Centauri A G2 4.38 Alpha Centauri B K0 5.71 Barnard's Star M3.5 13.25 Wolf 359 M5.5 16.64 Lalande 21185 M2 10.44 Sirius A A1 1.44 Sirius B A2 11.34 Epsilon Eridani K2 6.20 Lacaille 9352 M1 9.76 Ross 128 M4 13.53 61 Cygni A K5 7.48 61 Cygni B K7 8.31 Procyon A F5 2.65 Procyon B A0 12.98 Struve 2398 M3 11.17 Groombridge 34 M1.5 10.31 Epsilon Indi K4 6.98 Tau Ceti G8.5 5.68 Radioactive Dating Activity (due at Stage 2) (30 points) Brief Overview of Activity : Radioactive decay is one of the sources of the heat that drive the Earth's geologic activity. Radioactive decay also allows us to date rocks and determine the age of the Earth and other solar system bodies. Required Items: 36 coins, a calculator, pencil & paper. Procedure: In this activity you will simulate the radioactive decay of 36 atoms of a rare isotope of uranium, U-235. Uranium-235 has a half-life of 700 million years. Gather 36 coins and arrange them in a 6 x 6 grid with all of the coins facing heads up. Flip each coin into the air and then place it back in its original location on the grid. This represents the passage of 1 half-life (700 million years for this example). The coins that came up heads represent atoms that have not yet decayed; the coins that came up tails represent atoms that have decayed. Record the number of heads below. Next flip each one of the remaining heads-up coins once and place it back in its original location. 1.4 billion years have now passed by (2 x 700 million). Record the number of remaining heads below. Repeat this process until all coins are tails up. _______ Original number of U-235 atoms _______ Remaining number of U-235 atoms after 1st flip _______ Remaining number of U-235 atoms a f ter 2nd flip Add additional lines as needed. Questions: How many half-lives did it.