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Astronomy 101 The Solar System Tuesday, Thursday Tom Burbine tomburbine@astro.umass

Astronomy 101 The Solar System Tuesday, Thursday Tom Burbine tomburbine@astro.umass.edu. 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.

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Astronomy 101 The Solar System Tuesday, Thursday Tom Burbine tomburbine@astro.umass

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  1. Astronomy 101The Solar SystemTuesday, ThursdayTom 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. There is an Astronomy Help Desk that is open Monday-Thursday evenings from 7-9 pm in Hasbrouck 205. • There is an open house at the Observatory every Thursday when it’s clear. Students should check the observatory website before going since the times may change as the semester progresses and the telescope may be down for repairs at times. The website is http://www.astro.umass.edu/~orchardhill/index.html.

  4. Exam #2 • Average 74.1 • Grades from a 27.5 to a 100

  5. HW #10, #11, and #12 • Due March 30th at 1 pm

  6. Solar System • Sun • Eight Planets • Their moons • Dwarf Planets • Asteroids • Comets

  7. Sun

  8. Sun • 74% H • 25% He • Traces of everything else

  9. Mercury

  10. Venus

  11. Earth

  12. Earth’s crust • 46.6% O • 27.7% Si • 8.1% Al • 5.0% Fe • 3.6% Ca • 2.8% Na • 2.6% K • 2.1% Mg

  13. Moon

  14. Comet

  15. Mars

  16. Asteroid

  17. http://spaceguard.esa.int Hiroshima

  18. Meteorites chondrite Pallasite – mixtures of olivine and metal Iron

  19. Jupiter

  20. Jupiter • 90% H • 10% He • Traces of everything else

  21. Io

  22. Europa

  23. Saturn

  24. Saturn • 75% H • 25% He • Traces of everything else

  25. Uranus

  26. Neptune

  27. Pluto

  28. How do we determine what astronomical bodies are made of?

  29. How do we determine what astronomical bodies are made of? • Measure how they emit or reflect light • Tells you about their surfaces • Measure their physical properties • Tells you about their interiors

  30. Planetary densities mass Units are g/cm3 or kg/m3 1 g/cm3 = 1,000 kg/m3 But how do we determine mass?

  31. Use Newton’s Laws of motion… Where P is the period of a planet’s orbit a is the distance from the planet to the Sun G is Newton’s constant M is the mass of the Sun This assumes that orbits are circles, and that the mass of a planet is tiny compared to the mass of the Sun. Use this relation with P and a for the Earth, and you’ll get the mass of the Sun: MSun = 1.98892 x 1030 kg

  32. But we want to know the mass of a planet! and F = ma Where F is the gravitational force G is the constant of proportionality M and m are the two masses exerting forces r is the radius of the planet a is its acceleration due to gravity

  33. Re-arrange to get Solve for M, the mass of the Earth, by using a = 9.8 m/sec2 r = 6.4 x 106 m G = 6.67 x 10-11 m3/(kg sec2) MEarth = 5.9736 x 1024 kg VEarth = 1.0832 x 1021 m3 DEarth = 5515 kg/m3 = 5.515 g/cm3

  34. Volume • If you assume a planet is a sphere: • Volume = 4/3πr3

  35. Density = ρ = Mass/VolumeρEarth = 5.515 g/cm3 Liquid Hydrogen 0.07

  36. Density of water • Density of water is 1 g/cm3 • Density of water is 1,000kg/m3

  37. What do these densities tell us? Density

  38. How big is the Solar System?One boundary • Some scientists think that the furthest influence of the Solar System extends out to 125,000 astronomical units (2 light years). • Since the nearest star is 4.22 light-years away, the Solar System size could extend almost half-way to the nearest star. • Astronomers think that the Sun's gravitational field dominates the gravitational forces of the other stars in the Solar System out to this distance.

  39. What is out there? • The Oort Cloud (the source of long period comets) extends out to a distance of 50,000 AU, and maybe even out to 100,000 AU. • The Oort Cloud has never been seen directly. • Appears to exist because comets with extremely long orbits sometimes pass near the Sun and then head back out again. • The Oort cloud could have a trillion icy objects.

  40. Another possible boundary- Heliopause • Heliopause is the region of space where the sun's solar wind meets the interstellar medium. Solar wind's strength is no longer great enough to push back against the interstellar medium. • Solar wind – charged particles ejected from the Sun • Interstellar medium – gas and dust between stars • Heliosphere is a bubble in space "blown" into the interstellar medium • It is a fluctuating boundary that is estimated to be ~80-100 AU away

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