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 Spin and Orbit

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NoCoPilot

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PostSubject: Spin and Orbit   Sat Apr 28, 2018 11:40 pm

I need to do some research.

  • I believe all of the planets of our solar system are in the same plane (like the rings of Saturn) except for one (Uranus?  Neptune?) which has an elliptical orbit that goes above and below the plane.

  • I believe all of the planets spin the same direction, which is the same direction as their orbits -- except one.  Not sure which. Why is spin preserved from systems to individual bodies?

  • I believe all of the moons spin the same way too.  Our moon is tidally locked, showing the same face to Earth, but technically that's the same direction of spin, right?

  • What's the period of the Sun's rotation?  Do the larger planets spin slower?  Is the surface velocity relatively constant, so the smaller moons rotate faster?  Do Saturn's rings spin in lockstep with the surface of the planet, or lag?  Do all the rings spin in unison?

  • I know (or think I know...) that other solar systems in our galaxy are in different planes from our own, so we don't look at them on edge.  But then the discovery of extrasolar planets usually involves solar occlusions so maybe not.

  • The Earth has a polar tilt of 23º which causes our seasons.  But the Moon and the Sun seem to have no tilt relative to Earth?  Do other planets and moons have polar declination (is that the right term)?

  • Did the Voyager spacecraft go out in a spiral, traveling around the sun -- or straight out?  I think there were some gravity assists in its trajectory, which probably means a spiral path. But that would take a lot longer so maybe not.
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richard09

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PostSubject: Re: Spin and Orbit   Sun Apr 29, 2018 7:41 am

It seems you are wrong on some things but right on others. Trying to talk or write about this stuff is confusing as fuck.

Retrograde and prograde motion
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PostSubject: Re: Spin and Orbit   Sun Apr 29, 2018 8:38 am

Thanks for the link.

  • Venus and Uranus spin opposite from everybody else
  • Venus's axial tilt is 177 degrees, almost 180 degrees -- it's "north" is almost entirely "down."  Does this mean it's spin is the same, but the orientation is opposite?
  • Uranus's axial tilt is 97.77 degrees, so its north pole basically points toward the sun
  • Venus's day (period of rotation) is extremely long, 243 Earth days.  It's year (period of revolution) is almost exactly the same, 224.7 days -- almost a tidal lock
  • For comparison, Mercury also spins extremely slowly: 58.6 days.  Its year is only slightly longer, 87.97 days.  Half locked.  Days are half a year long.
  • Mars 1.03 days, 1.88 years
  • Jupiter 0.41 days (the gas giants all spin really fast!), 11.86 years
  • Saturn 0.45 days, 29.46 years
  • Uranus 0.72 days, 84.01 years
  • Neptune 0.67 days, 164.79 years
  • Copernican dynamics dictate that the period of revolution is dictated by the planet's mass and its distance from the sun, so that centrifugal force exactly equals gravitational pull
  • Orbital velocity ranges from 47.4 km/s for Mercury to 5.4 for Neptune
  • Perihelion÷aphelion (eccentricity of orbit) is .659 for Mercury, .987 for Venus, .967 for Earth, .829 for Mars, .907 for Jupiter, .893 for Saturn, .912 for Uranus, .978 for Neptune
  • Orbital inclination (degrees tilt off the plane): Mercury .205, Venus 3.4, Earth 0.0, Mars 1.9, Jupiter 1.3, Saturn 2.5, Uranus 0.8, Neptune 1.8
  • Pluto, the non-planet, has a very inclined orbit: 17.2
  • Obliquity to orbit (tilt of the poles): Mercury .034, Venus 177.4, Earth 23.4, Mars 25.2, Jupiter 3.1, Saturn 26.7, Uranus 97.8, Neptune 28.3
  • What causes obliquity I wonder?  Interesting that all planets -- except Jupiter and Mercury (and of course Venus and Uranus) -- tilt between 23 and 28 degrees
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PostSubject: Re: Spin and Orbit   Sun Apr 29, 2018 8:52 am

The sun's rotation varies with latitude -- the equator rotates every 24.47 days, the poles every 38.

That seems really fast for a body so big.

The Earth would have to rotate every 1.5 hours for centrifugal force to equal gravity (and the Earth would flatten into a disc).  I wonder how oblate the sun is?

Time for more research.
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PostSubject: Re: Spin and Orbit   Sun Apr 29, 2018 9:01 am

Quote :
The sun is the biggest and smoothest natural object in the solar system, perfect at the 0.001% level because of its extremely strong gravity," says study co-author Hugh Hudson of UC Berkeley. "Measuring its exact shape is no easy task."

"We have found that the surface of the sun has rough structure: bright ridges arranged in a network pattern, as on the surface of a cantaloupe but much more subtle," describes Hudson. During active phases of the solar cycle, these ridges emerge around the sun's equator, brightening and fattening the "stellar waist." At the time of RHESSI's measurements in 2004, ridges increased the sun's apparent equatorial radius by an angle of 10.77 +- 0.44 milli-arcseconds, or about the same as the width of a human hair viewed one mile away.
Source
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PostSubject: Re: Spin and Orbit   Sun Apr 29, 2018 9:23 am

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PostSubject: Re: Spin and Orbit   Sun Apr 29, 2018 9:34 am

Surface gravity (m/s²):

  • Mercury 3.7
  • Venus 8.87
  • Earth 9.8
  • Mars 3.71
  • Jupiter 24.92
  • Saturn 10.44
  • Uranus 8.87
  • Neptune 11.15

  • Sun 274

Source

Interesting(?) that the two retrograde planets have EXACTLY the same surface gravity. Must've been engineered that way by the inhabitants.
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PostSubject: Re: Spin and Orbit   Sun Apr 29, 2018 9:59 am

Mean temperature:
  • Venus 464 ℃
  • Uranus -195 ℃
Hardy inhabitants!
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PostSubject: Re: Spin and Orbit   Sun Apr 29, 2018 10:11 am

Interesting that the density of the gas giants is almost a third of the planets made of rock.
  • Mercury 5427 kg/m³, Venus 5243, Earth 5514, Mars 3933
  • Jupiter 1326, Saturn 687, Uranus 1271, Neptune 1638
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PostSubject: Re: Spin and Orbit   Sun Apr 29, 2018 2:40 pm

Quiz:
The mass of the sun is how many times larger than all the planets and their satellites put together?

  • one time
  • ten times
  • a hundred times
  • a thousand times
  • ten thousand times
  • a hundred thousand times
  • a million times
  • ten million times
  • a hundred million times
  • a thousand million times (a billion for us yanks)
  • ten thousand million times
  • a hundred thousand million times
  • a billion times (for the rest of the world)
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