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2020-05-03, 08:01 AM (ISO 8601)
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- Oct 2017
what is the distance between the Sun center and the two foci of the Earth orbit?
I'm having a hard time finding this information on google, most places say it's very close. How much? are the two focus inside the Sun ?
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2020-05-03, 09:00 AM (ISO 8601)
- Join Date
- Jun 2011
Re: what is the distance between the Sun center and the two foci of the Earth orbit?
One of the foci definitely is, as by definition for elliptical orbits.
If the Earth's eccentricity was zero, that would mean it was a circular orbit, and therefore both foci would be at the same place. Therefore the distance between the foci is related to the centricity so you might look in that direction.
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2020-05-03, 11:14 AM (ISO 8601)
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- Sep 2016
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2020-05-03, 11:15 AM (ISO 8601)
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- Feb 2007
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- Manchester, UK
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Re: what is the distance between the Sun center and the two foci of the Earth orbit?
Not necessarily--one of the foci is at the *barycentre* (e.g. the centre of mass) of the pair of bodies you're considering, which is not always inside either of them; it definitely isn't for the Pluto-Charon system, for instance, and neither is it true for the Sun and Jupiter (the barycentre for that is a few tens of thousands of kilometres above the Sun's surface).
You can calculate how far apart the two foci of the orbit are from the eccentricity and the semi-major axis--in the case of Earth this is 149.6 million kilometres and 0.0167, so the distance between the foci is 2 x 149.6 million x 0.0167, or about 5 million kilometres, which is much larger than the Sun's diameter; therefore, both foci cannot be inside the star no matter where they are. (I believe Kepler may have originally proved this and not been very happy about it, but I'm unable to find confirmation of that).
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2020-05-03, 11:49 AM (ISO 8601)
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- Jul 2008
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- Sweden
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Re: what is the distance between the Sun center and the two foci of the Earth orbit?
Okay so the Earth's periapsis (the lowest point of the orbit) is 147,098,074 km and apoapsis (the highest point of the orbit) is 152,097,701 km.
The average of these is 149,597,887.5 km (which is 1 AU to the precision of 1 in 1,000,000)
Does that answer your question?Black text is for sarcasm, also sincerity. You'll just have to read between the lines and infer from context like an animal
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2020-05-03, 01:56 PM (ISO 8601)
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- Oct 2010
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Re: what is the distance between the Sun center and the two foci of the Earth orbit?
I thought the sun/earth barycentre was just inside the skin of the sun. That was how solar flares were explained in my highschool course, the sun's tides were so extreme that it caused geysers when gravitation pulls hit right.
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2020-05-03, 02:45 PM (ISO 8601)
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- May 2017
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Re: what is the distance between the Sun center and the two foci of the Earth orbit?
No, that's probably the sun-jupiter barycentre (or, since it's talking about the dynamics of the sun, probably the barycentre of the entire solar system). The mass of the earth is negligible compared to that of the sun, so the barycentre is only off from the sun's centre by about 500 km. See this wikipedia page for the math: https://en.wikipedia.org/wiki/Barycenter
Last edited by DeTess; 2020-05-07 at 04:20 AM.
Jasnah avatar by Zea Mays
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2020-05-06, 04:22 AM (ISO 8601)
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- Oct 2017
Re: what is the distance between the Sun center and the two foci of the Earth orbit?
Thank you Guys