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Astronomy 101: Exploring the Solar System

Join us in Astronomy 101 to delve into the wonders of the solar system. Learn about celestial bodies, gravity, tides, and more through engaging content! Discover the secrets of space in this interactive course.

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Astronomy 101: Exploring the Solar System

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  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. Exam #1 • Average was 85 • Grades ranged from 40s to 100s

  6. HW #5 • Due Thursday

  7. A hypothesis is an educated guess, based on observation. Usually, a hypothesis can be supported or refuted through experimentation or more observation. A hypothesis can be disproven, but not proven to be true. • A scientific theory summarizes a hypothesis or group of hypotheses that have been supported with repeated testing. A theory is valid as long as there is no evidence to dispute it. Therefore, theories can be disproven. • A law generalizes a body of observations. At the time it is made, no exceptions have been found to a law.

  8. assume all mass is concentrated in the center of a body

  9. F = G M1 M2 r2 • The value of G was determined by Henry Cavendish between 1797-1798 • G = 6.67 x 10-11 m3/(kgs2) • http://blogs.howstuffworks.com/2009/04/13/diy-calculate-the-gravitational-constant-like-cavendish-did/ http://www.makingthemodernworld.org.uk/learning_modules/maths/06.TU.02/illustrations/06.IL.09.gif

  10. What is the attraction of two people in this room? F = G M1 M2 r2 • Say their masses are both 100 kg • Their distances are 10 meters apart • F = 6.67 x 10-11 m3/(kgs2) * 100*100 kg2/(10*10 m2) • F = 6.67 x 10-9 N = 0.0000000067 N • Remember the person weighs 980 N

  11. F = G M1 M2 r2 • How would the force between the two people change if they were only 5 meters apart instead of 10 meters? • A) Stay the same • B) Double (Increase by a Factor of 2) • C) Quadrupul (Increase by a Factor of 4) • D) halve (decrease by a factor of 2)

  12. F = G M1 M2 =G M1 M2=4 G M1 M2 (r/2)2 r2/4 r2 • How would the force between the two people change if they were only 5 meters apart instead of 10 meters? • A) Stay the same • B) Double (Increase by a Factor of 2) • C) Quadrupul (Increase by a Factor of 4) • D) halve (decrease by a factor of 2)

  13. Acceleration of gravity (g) Mis the Earth’s mass F = ma = G Mmr is the Earth’s radius r2 m is the mass of an object F is the force a is the acceleration a = G M r2 g = a = G M r2

  14. Acceleration of gravity (g) Mis the Earth’s mass g = G Mr is the Earth’s radius r2 g = 6.67 x 10-11 m3/(kgs2) * (6.0 x 1024 kg) (6.4 x 106 m) * (6.4 x 106 m) g = 9.8 m/s2

  15. Gravitational acceleration • Gravitational acceleration is different on different planets because they have different sizes and masses • Gravitational acceleration (on Moon) = 1.6 m/s² (0.165 g) • Gravitational acceleration (on Jupiter) = 24.8 m/s² (2.53 g)

  16. Experiment on the Moon • http://www.youtube.com/watch?v=5C5_dOEyAfk

  17. How things fall • Heavy and light objects fall at the same rate • The heavy object does not fall faster (as long as there is no air resistance) g = G M (does not depend on mass of object) r2

  18. How does gravity work? • Gravity distort space-time • http://www.hulu.com/watch/19766/spacerip-einsteins-messengers

  19. Escape velocity • Velocity above this will allow an object to escape a planet’s gravity For Earth: v = square root[(2 x 6.67 x 10-11 m3/(kgs2) x (6.0 x 1024 kg)] (6.4 x 106 m) v = square root [1.25 x 108 m2/s2] v = 11.2 x 103 m/s = 11.2 km/s v

  20. Escape velocity • Escape velocity is different on different planets because they have different sizes and masses • Escape velocity (on Moon) = 2.4 km/s • Escape velocity (on Jupiter) = 59.5 km/s

  21. What causes tides on earth? • Moon pulls on different parts of the Earth with different strengths • http://www.youtube.com/watch?v=Rn_ycVcyxlY • http://www.youtube.com/watch?v=aN2RM5wa1ek

  22. Forces on Water • Average Force on 1 kg water on Earth from Moon F = G Mm= 6.67 x 10-11 m3/(kgs2) * (7.35 x 1022 kg) * (1 kg) r2 (3.84 x 108 m) 2 • F = 3.33 x 10-5 N • Force of 1 kg on water on near-side of Earth from Sun F = G M m = 6.67 x 10-11 m3/(kgs2) * (7.35 x 1022 kg) * (1 kg) r2 (3.84 x 108 m -6.37 x 106 m) 2 • F = 3.44 x 10-5 N • Difference in forces is 1.1 x 10-6 N • Called Tidal Force

  23. Tidal force arises because the gravitational force exerted on one body by a second body is not constant across its diameter • Water flows so this tidal force causes the tides that are seen on Earth

  24. Effects on tides due to Sun • Sun exerts a stronger gravitational force on the Earth • But since farther away, the differential force from one side of the Earth to the other is smaller • Sun’s tidal effect is about one-half that of the Moon

  25. Forces on Water • Average Force on 1 kg water on Earth from Sun F = G Mm= 6.67 x 10-11 m3/(kgs2) * (2 x 1030 kg) * (1 kg) r2 (1.5 x 1011 m) 2 • F = 5.928889 x 10-3 N • Force of 1 kg on water on near-side of Earth from Sun F = G M m = 6.67 x 10-11 m3/(kgs2) * (2 x 1030 kg) * (1 kg) r2 (1.5 x 1011 m -6.37 x 106 m) 2 • F = 5.929392 x 10-3 N • Difference in forces is 5.0 x 10-7 N due to Sun • Difference in forces is 1.1 x 10-6 N due to Moon

  26. Remember • Force downwards is 9 Newtons on 1 kg of water • Water won’t be pulled off Earth • Water can flow

  27. Shoemaker-Levy 9 • Comet that hit Jupiter • Jupiter-orbiting comet • Broken apart by tidal forces • Discovered in 1993 • Hit Jupiter in 1994

  28. Roche Limit • The smallest distance at which a natural satellite can orbit a celestial body without being torn apart by the larger body's gravitational force (tidal forces). The distance depends on the densities of the two bodies and the orbit of the satellite. • If a planet and a satellite have identical densities, then the Roche limit is 2.446 times the radius of the planet. • Jupiter's moon Metis and Saturn's moon Pan are examples of natural satellites that survive despite being within their Roche limits

  29. Why is the Roche Limit important? • Comet Shoemaker-Levy 9's decaying orbit around Jupiter passed within its Roche limit in July, 1992, causing it to break into a number of smaller pieces. • All known planetary rings are located within the Roche limit

  30. The first impact occurred at 20:15 UTC on July 16, 1994 • Fragment A of the nucleus slammed into Jupiter's southern hemisphere at a speed of about 60 km/s. • Instruments on Galileo detected a fireball which reached a peak temperature of about 24,000 K, compared to the typical Jovian cloudtop temperature of about 130 K, before expanding and cooling rapidly to about 1500 K after 40 s.

  31. http://www.youtube.com/watch?v=tbhT6KbHvZ8

  32. Has this happened before?Ganymede

  33. Any Questions?

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