Monday, October 22, 2018

Uranus is the 7th planet



-  2140  -  Uranus is the 7th planet from the Sun.  All the rest of the planets spin like tops as they orbit the Sun.  But, Uranus rolls on its side.  It is the 3rd largest planet and can be seen with the naked eye.  Uranus orbits the Sun in 84 years with a radius of 1,864 million miles.  The Earth orbits at 93 million miles.  This great distance means that sunlight is 1/400th that of Earth‘s. 
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----------------------------------  2140  -  Uranus
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-  Uranus is the 7th planet from the Sun.  All the rest of the planets spin like tops as they orbit the Sun.  But, Uranus rolls on its side.  It is the 3rd largest planet and can be seen with the naked eye.  However, it is exceedingly dim and seeing it is quite a challenge.  Uranus was first discovered in 1781.  It was the first planet discovered using a telescope, a homemade telescope.
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-  Jupiter and Saturn are known as the gas giants.  Uranus and Neptune are known as the ice giants.  The atmosphere of Uranus is mostly hydrogen and helium but it also contains water ice, ammonia ice, and methane ice, plus some hydrocarbons.  Ice is not surprising since Uranus has the coldest atmosphere in the Solar System, -224F.
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-  ( See Review 2139 to learn about Neptune and its moon Triton)
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-  Uranus has 13 rings, 27 moons and a magnetosphere.  It is most unusual in the Solar System because its north pole points directly toward the Sun.  It orbits rolling on its side.  The wind speed on the surface is 560 miles per hour.
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-  Uranus orbits the Sun in 84 years with a radius of 1,864 million miles.  The Earth orbits at 93 million miles.  This great distance means that sunlight is 1/400th that of Earth‘s. 
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-  In the year 1783 orbit calculations were made but subsequent observations were always off what was calculated.  In 1841 astronomers first suggested this discrepancy must be due to an unseen planet, Planet X.  In 1846 the new planet was discovered exactly where calculations said it should be, it was named Neptune.
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-  Because of Uranus’ 98 degree tilt one half of the planet is always in daylight.  After half an orbit, 42 years, the other half is in constant daylight.  In between these extremes the equator experience  a day-night cycle with a 17 hour rotation.
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-  The theory for Uranus’ tilt is similar to the theory for the creation of our Moon.  Uranus most likely suffered a massive collision with another protoplanet during its early history.
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-  The Earth's orbital and magnetic field are offset by 12  degrees.  Uranus' are offset by 60 degrees.  This results in a corkscrewing magnetic field trailing millions of miles behind the planet.
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-  Uranus' subtle rings are not like Saturn's bright icy rings.  They are dark and reflect little light.  The rings are probably mostly ice but covered in organic methane and then baked dark by the radiation belt.  Uranus' moons are similarly camouflaged as well. 

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-  Two of the moons, Cordelia and Ophelia, are shepherd moons.  They orbit on either side of Uranus.  Their gravitational pull herds the small particles in the rings along their orbital path and keeps the rings from dissipating into space.
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-  At current count Uranus' has a total of 27 moons.  Some of the moonlets are only 2 to 9 miles diameter. 
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-  We said Uranus can be seen with the naked eye.  Naked eye visibility is put at an average Magnitude of +6.0, depending on the individual.  Uranus can appear +5.6 to +5.9 Magnitude which is very dim.  Its angular diameter is 3.7 arc seconds.  Saturn is 20 arc seconds and Jupiter is 45 arc seconds for comparison.  Uranus mass is 14.5 that of Earth‘s.  Its density is 1.29 grams/cm^3.
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-  Uranus’ magnetic field is tilted 59 degrees from the axis of rotation and does not originate at the planet’s center.  Theory has it that the magnetic field is not generated by a molten, solid core, but, rather by a water-ammonia ocean at some shallow depth under the surface.
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-  October 15, 2018.       1131
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 ---------------------   Monday, October 22, 2018         -------------------------
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