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quote:Originally posted by daveshortsI don't know what the total elipticalness of the solar system is, but I think that if you have several circular orbits interactions between the planets will tend to take the orbits away from the perfect circle into ellipses.
quote:Originally posted by Soul SurferSome of the thinking behind this question sounds a bit like the ancient theory that orbits must be circular because of the "perfection" of the circular shape.
quote:Firstly the solar system is not "elliptical". The elliptical orbits of the planets are in no way similar in their ellipticity or aligned in any particular direction.
quote:The normal orbit for one object about another is an ellipse. A circle is just an extreme case of an ellipse where everything happens to be precisely balanced.
quote: Funnily enough even if the orbits of all the planets were set to be perfect circles with their current periods. They would rapidly become elliptical because of the gravitational effects of the planets on each other.
quote:Originally posted by DoctorBeaverIf the gravity of planets affects all of the others, would it not be logical to assume that the orbits of Jupiter & Saturn - being the heaviest of the planets & the 2 with the strongest gravitational fields - would be more circular than the others? Is this the case?
quote:Originally posted by Soul SurferFirstly it is vital to understand that if we have just two small bodies (ie they don't collide) with some initial arbitrary relative velocity with respect to one another that are attracted by gravity towards each other from a great distance it is impossible for them to go into orbit around each other. The resulting orbit is hyperbolic and they just deflect each other's paths. The reason for this is that the relative angular momentum of the two bodies will always exceed the escape velocity of the system.If a closed orbit is to be created (using only gravity) it needs the interposition of a third gravitating body which slows the relative velocities down to below the escape velocity of the gravitating pair.
quote:The disk of material which formed around our sun only influenced the composition of the planets and there direction of travel around the sun.
quote:All planets orbiting a sun have elliptical orbits, they can't have anything else.All planets do affect each others orbits as all planets some more than others tug on the sun causing it to wobble, the same wobble which they look for to find planets orbiting distant suns. In our solar system the planets orbits are only slightly elliptical and are not far off circular. The reason being the large gas giants but mostly jupiter are quite far out and at the distance that they are, they are not large enough and do not produce enough gravity to tug on the sun very much. It’s this tugging or moving of the sun if you like which causes the planets to have noN circular orbits.Disclaimer I could be wrong ,but thinking about it I feel I’m right or at least could be
quote:Although there is no overall pattern of heavier planets having greater eccentricity than lighter ones, it does seem that where a heavier and lighter planet are in adjacent orbits, the heavier of the two has the more eccentric orbit.
quote:Originally posted by DoctorBeaverquote:Although there is no overall pattern of heavier planets having greater eccentricity than lighter ones, it does seem that where a heavier and lighter planet are in adjacent orbits, the heavier of the two has the more eccentric orbit.The HEAVIER of the 2 has the more eccentric orbit? That would imply that a small planet has a greater influence over a large planet than does a large planet over a small 1. That doesn't sound right to me."There is no such thing on earth as an uninteresting subject; the only thing that can exist is an uninterested person."G K Chesterton
quote:At the moment the earth orbit is very circular however every every 100,000 years and every 413,000 years it goes through a cycle where it becomes more eccentric.
quote:Originally posted by ukmickyAt the moment the earth orbit is very circular however every every 100,000 years and every 413,000 years it goes through a cycle where it becomes more eccentric. Reading about it some believe the cycle is to long to be caused from gravitational forces within the solar system and must be caused through external influences like dark matter or even companion stars ?. There does seems to be much speculation in the scientific community as to the influences and reasons regarding planetary orbits but it seems to me that most of it is guesswork.Michael
quote:Nemesis is the name given to a hypothetical red dwarf star or brown dwarf, orbiting the Sun at a distance of about 50,000 to 100,000 AU, somewhat beyond the Oort cloud. Richard A. Muller suggests that the most likely object is a red dwarf with magnitude between 7 and 12 . Such a bright object would undoubtedly already be in existing star catalogs, but its true nature would only be detectable by measuring its parallax; due to orbiting the Sun it would have a very low proper motion and would escape detection by proper motion surveys that have found stars like the 9th magnitude Barnard's star.Nemesis' existence was proposed by Muller in 1984 (Nature, vol 308, pp 715-717, 1984) to explain an apparent 26-million year cycle in the occurrence of mass extinctions on Earth as noted by Raup and Sepkoski.According to the theory, Nemesis periodically (roughly every 26 million years), passes through a denser region of the Oort cloud, disrupting the orbits of comets, and sending millions of comets into the inner solar system and potential collision with the Earth. It was initially nicknamed the "death star" (after the fictional Star Wars weapon), although this nickname has fallen out of usage.No direct evidence for Nemesis has been found, however, and the existence of a periodicity in the Earth's series of mass extinctions is disputed.It is also worth noting that Matese and Whitman have suggested that the cycle might be caused by the solar system oscillating across the galactic plane. These oscillations may lead to gravitational disturbances in the Oort cloud with the same proposed consequences as the orbit of "Nemesis". However, the period of oscillation is not well-constrained observationally, and may differ from the needed 26 million years by as much as 40%.If Nemesis exists, it may be detected by the planned Pan-STARRS astronomical survey, or similar future projects.
quote:Originally posted by ukmickyAt the moment the earth orbit is very circular however every every 100,000 years and every 413,000 years it goes through a cycle where it becomes more eccentric. Reading about it some believe the cycle is to long to be caused from gravitational forces within the solar system and must be caused through external influences like dark matter or even companion stars ?.