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Astronomy 100 Class Schedule and Grading Information

This is the class schedule for Astronomy 100, including exam dates, topics covered, and grading information. It also includes important assignments and details about the Milky Way galaxy.

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Astronomy 100 Class Schedule and Grading Information

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  1. Astronomy 100Tuesday, Thursday 2:30 - 3:45 pmTom Burbinetburbine@mtholyoke.eduwww.xanga.com/astronomy100

  2. Exam • Average = 30.3/40 = 76% • Grades ranged from 0 to 40 • If you guess randomly, a 0 should happen 0.013% of the time • Should happen every 7523 tests

  3. Grade Distribution • 2 scores between 0 and 10 • 19 scores between 11 and 20 • 47 scores between 21 and 25 • 66 scores between 26 and 30 • 112 scores between 31 and 35 • 65 scores between 36 and 40

  4. Schedule • Apr 12  Tue  The Milky Way                                              • Apr 14  Thu      Galaxies                                                   • Apr 19  Tue        Life of a Galaxy                                        • April 21 Thu No class • Apr 26  Tue       Dark Matter                                                 • Apr 28  Thu      Cosmology and the Big Bang                         • May 3   Tue       Is there life elsewhere in the Solar System?     • May 5   Thu      Is there life elsewhere in the Universe?           • May 10  Tue      Exam 4 (material from April 12 – May 5) • May 12  Thu      Exam 5 (Comprehensive) • May 20 Fri Final Exam (Comprehensive) (Optional)

  5. Exam 5 and Final • Cumulative • I will take 10 questions from Exams 1-4 • No question will be exactly the same as ones on previous exams • Most questions will be very similar to those on previous exams

  6. HW and PRS • You need 20 PRS points to get 10% of your grade 100% • You need 20 HW points to get 10% of your grade 100% • We will use the PRS about twice a class • We will have about 10 more HW points

  7. Exams • I am taking the top 4 exams out of 6 exams

  8. If your exam average is 55% and your HW/PRS score is 100%, your average is 64% • If your exam average is 60% and your HW/PRS score is 100%, your average is 68% • If your exam average is 65% and your HW/PRS score is 100%, your average is 72% • If your exam average is 70% and your HW/PRS score is 100%, your average is 76% • If your exam average is 75% and your HW/PRS score is 100%, your average is 80% • If your exam average is 80% and your HW/PRS score is 100%, your average is 84% • If your exam average is 85% and your HW/PRS score is 100%, your average is 88% • If your exam average is 90% and your HW/PRS score is 100%, your average is 92%

  9. Grading • I want a class average at the end of the semester (top 4 exam scores, PRS, HW) to be at least 80% • If the class average at the end of the semester is less than 80% • I will multiply everybody’s average by a number that equals ___________80%______________ class average at end of semester

  10. Grading • If the class average is 80% or higher, your grade will be based on your top 4 exam scores, PRS, and HW

  11. If the class average is 80% or higher, the grade distribution will be something like this • A 92.50 - 100 • A- 89.50 – 92.49 • B+ 87.50 – 89.49 • B 82.50 – 87.49 • B- 79.50 – 82.49 • C+ 77.50 – 79.49 • C 72.50 – 77.49 • C- 69.50 – 72.49 • D+ 67.50 – 69.49 • D 62.50 – 67.49 • D- 59.50 – 62.49 • ? below 59.49

  12. OWL assignment (Due Thursday) • There is be an OWL assignment due on Thursday April 14 at 11:59 pm. • There are 15 questions and a perfect score will give you 2 homework points.

  13. Homework Assignment(Due May 3) • Make up a test question for next test • Multiple Choice • A-E possible answers • 1 point for handing it in • 1 point for me using it on test • The question needs to be on material that will be on the 3rd exam • 15 people got extra HW credit for me using their question (or inspiring a question)

  14. What is a Galaxy? • A Galaxy is a huge collection of stars that are bound together by gravity

  15. Number of Galaxies • There are thought to be 80 billion galaxies in the observable universe

  16. We live • We live in the Milky Way Galaxy • Thought to be 13.6 ± 0.8 billion years old

  17. Why is it called Milky Way? • It looked like a flowing ribbon of Milk to the Greeks

  18. Milky Way • Contains between 200 and 400 billion stars • Diameter is 100 thousand light years across

  19. PRS question • What two elements are the two largest constituents of the Milky Way Galaxy? • A) Helium and Carbon • B) Helium and Oxygen • C) Hydrogen and Iron • D) Carbon and Iron • E) Hydrogen and Helium

  20. PRS question • What two elements are the two largest constituents of the Milky Way Galaxy? • A) Helium and Carbon • B) Helium and Oxygen • C) Hydrogen and Iron • D) Carbon and Iron • E)Hydrogen and Helium

  21. Our Galaxy • There is a disk part • And Spherical Part –Bulge and Halo

  22. Disk • The disk includes all of the material (gas, dust, stars, and star clusters) which are confined to the plane of rotation of the galaxy • Contains lots of gas and dust and is therefore the site of active star formation • Lots of blue stars (O and B stars)

  23. Why are O and B stars evidence of active star formation? • A) Because they tend to be massive • B) Because they tend to be older • C) Because they tend to be younger • D) Because they tend to be less massive • E) Because they tend to be cooler

  24. Why are O and B stars evidence of active star formation? • A) Because they tend to be massive • B) Because they tend to be older • C) Because they tend to be younger • D) Because they tend to be less massive • E) Because they tend to be cooler

  25. Spiral Arms • 6 spiral arms

  26. Spiral Arms • Can’t be fixed patterns of stars • Stars nearer the center would complete an orbit much quicker than stars farther out • Would cause the arms to wrap up into a tight coil • We do not see that among spiral galaxies

  27. Spiral Arms • Spiral Arms are actively forming new stars • In spiral arms, see clusters of young, bright, blue stars • In spiral arms, we also see lots of gas and dust • Between the arms, you see old, red stars

  28. Bulge • The bulge is at the center of the galaxy, is a flattened spheroid • This is a high density region where red stars predominate, which are very old and about 10 billion years old • There is growing evidence for a very massive black hole at its center

  29. Rotation curve

  30. Rotation curve

  31. Things you need to remember • Higher the Force of Gravity • The faster the velocity of an object rotating around a larger object

  32. Balancing Forces • Like a spinning hammer thrower • Faster you spin the hammer • Stronger the Force needed to keep it from flying off

  33. Rotation Curve • Rotation curve of galaxy does not fall off with distance from center • The mass of our galaxy is not concentrated in center • More evenly distributed

  34. What’s the problem • The stars in the disk do not have enough mass to produce this rotation curve • The unseen mass is thought to be primarily in the halo

  35. Dark Matter • Most (~90%) of the Milky Way Galaxy is thought to be made of Dark Matter • Dark Matter is matter where its force of gravity can be felt but you can’t actually see it

  36. Possible Dark Matter Candidates • neutrinos with mass • undetected brown dwarfs • white dwarf stars • black holes • exotic subatomic particles

  37. Halo • The halo is a diffuse spherical region, which surrounds the disk. • It has a low density of old stars mainly in globular clusters (these consist of between 10,000 - 1,000,000 stars). • The halo is believed to be composed mainly of dark matter

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