Survey of Astronomy

1. Chapter 13 • Uranus & Neptune Survey of Astronomy Astro1010-lee.com twlee2016@gmail.com

2. Chapter 13 Uranus was Discovered in 1781 by William Herschel; first planet to be discovered in recorded history. Survey of Astronomy Astro1010-lee.com Little detail can be seen from Earth; arrows point to three of Uranus’s moons. twlee2016@gmail.com

3. Chapter 13 • William Herschel • Born in Germany he Anglicized his name when he came to England with the Hanover Kings. He was a musician from a musical family. • As an amateur Astronomer he looked at the sky with telescopes he built himself. Among other things in the sky he found what he thought was a comet. After further study he realized he had found a planet, the first in recorded history. Because of the fame of that discovery he became the Court Astronomer to King George III Survey of Astronomy Astro1010-lee.com twlee2016@gmail.com

4. Chapter 13 Most of the planets have their axes slightly tipped with respect to the plane of their orbits. Uranus is unusual in that it is tipped more than 90 degrees. As a result the rotation of the planet is retrograde. Survey of Astronomy Here we see Earth tipped 23.5 degrees and Uranus is tipped 98 degrees Astro1010-lee.com twlee2016@gmail.com

5. Chapter 13 During the Voyager encounter in l985 we only saw a featureless face as the Sun shone on the pole of the planet. Several years later When the HST looked at it we could see stripes and storms. Survey of Astronomy Astro1010-lee.com twlee2016@gmail.com

6. Chapter 13 As the Uranus axis of rotation lies almost in the plane of its orbit , the seasonal variations are extreme Survey of Astronomy Astro1010-lee.com twlee2016@gmail.com

7. Chapter 13 Rings around Uranus were discovered from Earth and we saw 3 narrow rings and 2 broad rings. The Voyager saw a system of hundreds of ringlets. The streaks are stars seen through the Uranus broad but thin ring system Survey of Astronomy Astro1010-lee.com twlee2016@gmail.com

8. Chapter 13 The moon Miranda has large chunks of rock and large fields of ice. It looks like it has been shattered in the near past and is now pulling itself back together. All of the parts have not yet found their final places. Survey of Astronomy Astro1010-lee.com twlee2016@gmail.com

9. Chapter 13 The Titus-Bode Rule is a handy approximation to Keller's 3rd law to demonstrate the distances of the planets from the Sun. It has no scientific significance. Survey of Astronomy Astro1010-lee.com twlee2016@gmail.com

10. Chapter 13 Neptune was discovered 1846, after analysis of Uranus’s orbit indicated its presence. Any new planet could not fit the Titus Bode Rule, hence the English and French Astronomical Societies ruled out another Planet. However, an Englishman, Adams , and a Frenchman, Le Verrier , gave their calculations to a German, John Gottfried Galle, who found Neptune immediately Survey of Astronomy Astro1010-lee.com twlee2016@gmail.com

11. Chapter 13 Details of Neptune cannot be made out from Earth. The arrows point to the moons Triton and Nerid Survey of Astronomy Astro1010-lee.com twlee2016@gmail.com

12. Chapter 13 Voyager found a Great Dark Spot. It was deter- mined to be a large storm. There were other smaller storms. Of special interest were the fast moving white clouds, demonstrating that the winds were the fastest in the Solar System. Survey of Astronomy Astro1010-lee.com twlee2016@gmail.com

13. Chapter 13 The rings of Neptune were discovered from the Earth but they looked like arcs. Voyager found complete rings but some of them were ’lumpy’. Neptune has five rings, three narrow and two broad. Our ring theories have been badly stretched by these rings. Rings do NOT seem to obey any rules. Survey of Astronomy Astro1010-lee.com twlee2016@gmail.com

14. Chapter 13 Two moons, Triton and Nerid, were discovered from the Earth. Eleven more were found by Voyager. The moon of most interest is Triton. Triton is unique in many ways. It’s temperature is the lowest of any body in the Solar System that we have visited, 32 deg. K. It has an atmosphere, high winds, active geysers and evidence of plate tectonics, frozen lakes and water volcanoes. Survey of Astronomy Astro1010-lee.com twlee2016@gmail.com

15. Chapter 13 Triton revolves around Neptune retrograde and it rotates on its axis retrograde. The tidal forces and the retrograde motion will one day cause Triton to crash into the planet. Survey of Astronomy Astro1010-lee.com twlee2016@gmail.com

16. Chapter 13 Nitrogen geysers have been observed on Triton, contributing to the surface features Survey of Astronomy Astro1010-lee.com Also, there appear to be frozen water lakes and ice volcanoes on Triton twlee2016@gmail.com

17. Chapter 13 Uranus and Neptune are very similar. UranusNeptune Mass 14.5 × E 17.1 × E Radius 4.0 × E 3.9 × E Density 1.3 x H2O 1.6 x H2O Survey of Astronomy Astro1010-lee.com twlee2016@gmail.com

18. Chapter 13 • Uranus and Neptune both have substantial magnetic fields, but at a large angle to their rotation axes. The rectangle within each planet shows a bar magnet that would produce a similar field. Note that both Uranus’s and Neptune’s are significantly off center. Survey of Astronomy Astro1010-lee.com twlee2016@gmail.com

19. Chapter 13 Magnetic fields of Uranus and Neptune must not be produced by dynamos, as the other planets’ fields seem to be. Interior structure of Uranus and Neptune, compared to that of Jupiter and Saturn Survey of Astronomy Astro1010-lee.com twlee2016@gmail.com

20. Chapter 13 End of Chapter 13 Survey of Astronomy Astro1010-lee.com twlee2016@gmail.com

21. Chapter 13 Survey of Astronomy Astro1010-lee.com twlee2016@gmail.com

22. Chapter 13 Survey of Astronomy Astro1010-lee.com twlee2016@gmail.com

23. Chapter 13 Survey of Astronomy Astro1010-lee.com twlee2016@gmail.com