1. [2 pts] Draw an HR diagram that shows the location of the Main Sequence, Giant Branch, Horizontal Branch, and White Dwarfs. Be sure that you know how stars evolve on this diagram.

2. [2 pts] Constuct an HR diagram (on graph paper or with
the aid of a computer plotting program - no freehand
sketches acceptable) of the 25 brightest stars
in the night sky, and of the 25 nearest stars to the Sun.
Each plot should range from 10^{-5}L_{SUN}
to 10^{5}L_{SUN} on the y-axis, and
from 2500K to 30000K on the x-axis. Remember that HR diagrams
are plotted in logs, with red stars on the right.

3. [1 pt] What do the differences in these two diagrams tell us about the frequency of massive, hot stars vs. low mass, cool stars? Which diagram is a better representation of the true distribution of stars in our galaxy and why?

4. [2 pts] Use the equation L = constant*R^{2}T^{4},
where L is the stellar luminosity and R is the stellar radius,
to show that objects with the same radii fall on a line in the HR
diagram. [HINTS: remember that the equation of a line is y = mx+b,
where m is the slope and b is the y-intercept; what variables in
the HR diagram correspond to x and y?; review properties of logs]

5. [2 pts] Draw lines of 0.01 R_{SUN}, 1 R_{SUN}, and 100 R_{SUN}
in an HR diagram, and show where the Sun, Wolf 359, and Betelguese lie.

6. [1 pt]If the Sun were the size of Betelguese, what would it look like from the Earth?

**The Brightest 25 Stars as seen at Night from Earth**

Star Name | Temperature | Luminosity/L_{SUN} |

Sirius | 9900 | 24 |

Canopus | 6700 | 1600 |

Arcturus | 4100 | 115 |

Alpha Centauri | 5800 | 1.6 |

Vega | 10400 | 63 |

Capella | 5200 | 180 |

Rigel | 14000 | 63000 |

Procyon | 6600 | 8 |

Betelguese | 2800 | 10000 |

Achernar | 16000 | 1260 |

Beta Centauri | 25000 | 2250 |

Altair | 7800 | 11 |

Aldebaran | 3200 | 200 |

Spica | 25000 | 1000 |

Antares | 2900 | 1000 |

Fomalhaut | 9300 | 16 |

Pollux | 4400 | 40 |

Deneb | 9600 | 63000 |

Beta Crucis | 25000 | 10000 |

Regulus | 14000 | 200 |

**The Closest 25 Stars**

Star Name | Temperature | Luminosity/L_{SUN} |

Sun | 5800 | 1.0 |

Alpha Cen A | 5800 | 1.6 |

Alpha Cen B | 5250 | 0.45 |

Alpha Cen C | 3000 | 6x10^{-5} |

Barnard's Star | 3000 | 4.5x10^{-4} |

Wolf 359 | 2500 | 2x10^{-5} |

Lalande 21185 | 3500 | 5.5x10^{-3} |

Luyten 726-8A | 2800 | 6x10^{-5} |

UV Ceti | 2800 | 4x10^{-5} |

Sirius A | 9900 | 24 |

Sirius B | 20000 | 0.003 |

Ross 154 | 3000 | 4.8x10^{-4} |

Ross 248 | 2800 | 1.1x10^{-4} |

Epsilon Eridani | 4900 | 0.3 |

Luyten 789-6 | 2700 | 1.4x10^{-4} |

Ross 128 | 3000 | 3.6x10^{-4} |

61 Cyg A | 4400 | 0.083 |

61 Cyg B | 4000 | 0.040 |

Epsilon Indus | 4400 | 0.13 |

Procyon | 6600 | 8 |