Survey of Astronomy Astro1010-lee.com [email protected] Chapter 13 Uranus & Neptune.
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Survey of Astronomy A s t r o 1 0 1 0 - l e e . c o m [email protected] om Chapter 13 Uranus & Neptune
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Transcript of Survey of Astronomy Astro1010-lee.com [email protected] Chapter 13 Uranus & Neptune.
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Chapter 13Uranus was Discovered in 1781 by
William Herschel; first planet to be discovered in recorded history.
Little detail can be seen from Earth; arrows point to three of Uranus’s moons.
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Chapter 13William 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
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Chapter 13Most 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.
Here we see Earth tipped 23.5 degrees and Uranus is tipped 98 degrees
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Chapter 13During 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.
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Chapter 13As the Uranus axis of rotation lies almost in
the plane of its orbit , the seasonal variations are extreme
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Chapter 13Rings 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
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Chapter 13The 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.
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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.
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Chapter 13Neptune 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
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Chapter 13Details of Neptune cannot be made out
from Earth. The arrows point to the moons Triton and Nerid
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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.
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Chapter 13The 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.
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Chapter 13Two 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.
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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.
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Chapter 13Nitrogen geysers have
been observed on Triton, contributing to the surface features
Also, there appear to be frozen water lakes and ice volcanoes on Triton
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Chapter 13
Uranus and Neptune are very similar.
Uranus NeptuneMass 14.5 × E 17.1 × E Radius 4.0 × E 3.9 × EDensity 1.3 x H2O 1.6 x H2O
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Chapter 13
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.
Uranus and Neptune both have substantial magnetic fields, but at a large angle to their rotation axes.
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Chapter 13Magnetic 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
