Astronomy 101: The Solar System Course

1. Astronomy 101The Solar SystemTuesday, Thursday2:30-3:45 pmHasbrouck 20Tom Burbinetomburbine@astro.umass.edu

2. Course • Course Website: • http://blogs.umass.edu/astron101-tburbine/ • Textbook: • Pathways to Astronomy (2nd Edition) by Stephen Schneider and Thomas Arny. • You also will need a calculator.

3. Office Hours • Mine • Tuesday, Thursday - 1:15-2:15pm • Lederle Graduate Research Tower C 632 • Neil • Tuesday, Thursday - 11 am-noon • Lederle Graduate Research Tower B 619-O

4. Homework • We will use Spark • https://spark.oit.umass.edu/webct/logonDisplay.dowebct • Homework will be due approximately twice a week

5. Astronomy Information • Astronomy Help Desk • Mon-Thurs 7-9pm • Hasbrouck 205 • The Observatory should be open on clear Thursdays • Students should check the observatory website at: http://www.astro.umass.edu/~orchardhill for updated information • There's a map to the observatory on the website.

6. Final • Monday - 12/14 • 4:00 pm • Hasbrouck 20

7. HW #9 • Due today

8. HW #10 • Due Oct. 29

9. Exam #2 • Average was a 75 • Grades from 100s to a 27.5 • http://web.mit.edu/thb/www/exam2a.answers.doc • Average (80% exams, 20% HW) for people who took both exams is ~81

10. 32 Extrasolar planets were just announced The new alien planets, which bring the known count beyond 400, were found with the HARPS spectrograph on the European Southern Observatory's 3.6-m telescope in La Silla, Chile. Some just five times the mass of Earth Others five times heftier than giant Jupiter http://www.msnbc.msn.com/id/33379852/ns/technology_and_science-space/

11. Radioactive Decay

12. http://academic.brooklyn.cuny.edu/geology/leveson/core/topics/time/graphics/radio1.gifhttp://academic.brooklyn.cuny.edu/geology/leveson/core/topics/time/graphics/radio1.gif

15. What are the assumptions to get an age?

16. What are the assumptions? • No loss of parent atoms • Loss will increase the apparent age of the sample. • No loss of daughter atoms • Loss will decrease the apparent age of the sample. • No addition of daughter atoms or if daughter atoms was present when the sample formed • If there was, the age of the sample will be inflated • These can possibly be all corrected for

17. Basic Formula • Number of daughter atoms formed = number of parent atoms consumed • If there were daughter atoms originally there • D – Do = no - n • Remember: n = noe-λt so no = n eλt • D- Do = n eλt– n • D = Do + n (eλt– 1)

18. Commonly Used Long-Lived Isotopes in Geochronology

19. How do you determine isotopic values?

20. How do you determine isotopic values? • Mass Spectrometer

21. It is easier • To determine ratios of isotopic values than actual abundances

22. Example • 87Rb  87Sr + electron + antineutrino + energy • Half-life is 48.8 billion years • 87Sr = 87Srinitial + 87Rb (eλt– 1) • Divide by stable isotope • 87Sr = 87Srinitial + 87Rb(eλt– 1) 86Sr 86Sr 86Sr

23. Example • Formula for line • 87Sr = 87Srinitial + (eλt– 1)87Rb 86Sr 86Sr 86Sr y = b + m x

24. http://www.asa3.org/aSA/resources/wiens2002_images/wiensFig4.gifhttp://www.asa3.org/aSA/resources/wiens2002_images/wiensFig4.gif

25. = (eλt – 1)

26. Carbon-14 • 99% of the carbon is Carbon-12 • 1% is Carbon-13 • 0.0000000001% is Carbon-14 • The half-life of carbon-14 is 5730±40 years. • It decays into nitrogen-14 through beta-decay (electron and an anti-neutrino are emitted).

27. Due to Carbon-14’s short half-life, can only date objects up to 60,000 years old

28. Plants take up atmospheric carbon through photosynthesis http://hyperphysics.phy-astr.gsu.edu/hbase/nuclear/cardat.html

29. When something dies, it stops being equilibrium with the atmosphere http://hyperphysics.phy-astr.gsu.edu/hbase/nuclear/cardat.html

30. Why is Carbon-14 still present if it has such a short half-life?

31. Why is Carbon-14 still present if it has such a short half-life? • Cosmic rays impact Nitrogen-14 and create Carbon-14 • Cosmic rays are energetic particles (90% are protons) originating from space. From the Sun (solar cosmic rays) or outside the solar system (galactic cosmic rays) • n + 14N → 14C + p

32. http://en.wikipedia.org/wiki/Image:Radiocarbon_bomb_spike.svghttp://en.wikipedia.org/wiki/Image:Radiocarbon_bomb_spike.svg

33. Composition of the Planets

34. Different bodies have different densities • Density = Mass/Volume • M = 42d3/GP2 V =4/3R3

35. Life of a Star • A star-forming cloud is called a molecular cloud because low temperatures allow Hydrogen to form Hydrogen molecules (H2) • Temperatures like 10-50 K

36. Region is approximately 50 light years across

37. Condensing • Interstellar clouds tends to be lumpy • These lumps tend to condense into stars • That is why stars tend to be found in clusters

38. Protostar • The dense cloud fragment gets hotter as it contracts • The cloud becomes denser and radiation cannot escape • The thermal pressure and gas temperature start to rise and rise • The dense cloud fragment becomes a protostar

40. When does a protostar become a star • When the core temperatures reaches 10 million K, hydrogen fusion can start occurring

42. Formation of Solar System • Solar Nebula Theory (18th century) – Solar System originated from a rotating, disk-shaped cloud of gas and dust • Modern theory is that the Solar System was born from an interstellar cloud (an enormous rotating cloud of gas and dust)

43. Composition • ~71% is Hydrogen • ~27% is Helium • ~2% are other elements (Fe, Si, O) in the form of interstellar grains

44. Show animation

45. Dust grains collide and stick to form larger and larger bodies. • When the bodies reach sizes of approximately one kilometer, then they can attract each other directly through their mutual gravity, becoming protoplanets • Protoplanets collide to form planets • Asteroids such as Ceres and Pallas are thought to be leftover protoplanets

47. Condensation – conversion of free gas atoms or molecules into a liquid or solid • Volatile – Elements or compounds that vaporize at low temperatures