Many thanks for these excellent answers Grant. Some points of clarification if I may
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Originally Posted by grant hutchison
The alignment is happenstance, since it will disappear as the sun moves along its orbit.
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Why is that? If you think of the solar system as like a snowplough pushing its way around the Milky Way, the blade has pitch of sixty degrees but zero yaw. Would continuing this setting mean the ecliptic will stay aligned to the galactic centre?
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Originally Posted by grant hutchison
I don't know about "spiral". The sun's movement is clockwise around the galaxy when viewed from galactic north.
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What I was asking is, if you take your picture, which is a static shot of the solar system against the galaxy at one moment in time, and extend it through time by depicting the planets as spirals around the cylindroid formed by the movement around the galaxy, then do the planets also go clockwise viewed from solar north?
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Originally Posted by grant hutchison
There are various estimates. The Local Standard Of Rest is moving at around 200 km.s-1: that's circular velocity for our distance from the galactic centre. Relative to the LSR, the sun has its own velocity: 14 km.s-1 faster around the galaxy, inwards towards the galactic centre at 10 km.s-1, and towards galactic north at 7 km.s-1. (Figures from Frank Bash; there are other estimates.) The sun will take about 240 million years to go once around the galaxy.
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Great! By my further calculation this means we go 1500 trillion kilometres per galactic cycle! These figures show the sun moves over six billion kilometres per year. So November 4 next year we will be 6.3 billion kilometres (42 AU) further on. (I'm sure that AU figure was the answer to something). Over the Jupiter 11.85 year cycle the system will have moved 75 billion km. Jupiter's orbital diameter of 1.6 billion km depicted as a spiral would loop back to itself with a period almost 100 times the spiral diameter.
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Originally Posted by grant hutchison
The sun is north of the galactic plane at present, and moving farther from it.
The period is about 65 million years. The amplitude is about 200 light-years either side of the galactic plane. Grant Hutchison
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Thanks Grant, am I right to understand the unit of the 65 MY period is two halves of a sine wave, so the period is the time taken to return to the same position of a wave function? Does this mean the sun spends an equal amount of time north and south of the galactic plane? For example, over the 65 million years since the dinosaurs, has the sun been equally north and south of the galactic plane?