Talk:Orbit (celestial mechanics)

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Contents 1 Miscellaneous 2 open orbits 3 Kepler 4 Article Name 5 Example calculations 6 Table of orbital data 7 Stability of planetary orbits 8 Requested move 8.1 Survey 8.2 Discussion 9 Understanding Orbits Sections 10 Tilted Cannon?

[edit] Miscellaneous

where can i find information about earth's orbit around the sun? no link seems to lead to this information. -tom Are all planets orbiting the sun anti clock wise? -peg

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Most recent update was mine. My main intention was to fix the incorrect assertion in the previous version that inner planets has more circular orbits. This was in the introduction, so I placed the correction there. As a result the intro now looks a bit bloated with material duplicated below. -- Alan Peakall 17:03, 5 Sep 2003 (UTC)

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This page was moved to orbit (physics) and turned into a disambig page for a bit; this does not really make sense, since almost all inbound links were in the gravitational orbit sense. I moved the disambig page to orbit (disambiguation), and moved orbit (physics) back here. -- The Anome 00:10, 30 Aug 2004 (UTC)

You could also ask User:BenjBot to solve such a problem. I would not say that orbit in physics is the first thing for orbit. Tosha 04:00, 30 Aug 2004 (UTC)

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It's also a brand of gum... Someone should add that.

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Earth's orbit is neither clock wise nor counter-clock wise, and it is both. One cannot truely answer the question because it is relative to your perspective. The orbit is either clockwise or counter-clockwise depending on whether you look at it from the "top" (if it is truely the top), or if you look at it from the "bottom" (if it truely is the bottom).

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The equation of the orbit described by the particle is thus:

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Should the second : be a : ? Otherwise it doesn't make any sense, what would l be? DavidMcKenzie 16:00 21 July 2005

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Remembered what the l was: it's the semi-latus_rectum. Added a link to that and cleared up the ambiguity between the 1 and the L. DavidMcKenzie 16:51 21 July 2005

[edit] open orbits

Is it common for astronomers to call hyperbolic and parabolic motion orbits? To the layman, this is confusing. Orbits in common language implies periodic motion. If this is a common way for astronomers to speak, there should be an introductory sentence that explains this. Like this: "Astronomers commonly refer to any motion of one body relative to another as an orbit, even if the motion is not in a circular or eliptical path." It seems this article could use some translation into common English! -- Samuel Wantman 06:01, 30 July 2005 (UTC)

For astronautical engineers, spacecraft engineers and astronomers, I think it is common. Looking at the definition of "orbit" states that it is a "path" and I cant really see an implication of periodicity. The Greeks are probably the ones who coined the term "orbita" (path) for the wanderers (planets) as they probably did not observe open orbits (how could they have?). Open orbits were probably a mathematical result first before they were observed, hence the misnomer. Wicak 09:19, 3 August 2005 (UTC)

[edit] Kepler

I wonder if the statement "Kepler analyzed mathematically" is correct? As I recall reading, he made many many measurements over years, before arriving at a mathematical result. Empirical deductions would be a more accurate description. Wicak 09:12, 3 August 2005 (UTC)

[edit] Article Name

Shouldn't this article (Planetary orbit) be renamed Orbit (Astronomy) or Orbit (Celestial mechanics)? Planets are not the only thing that orbit. The star also orbits around the planet and two stars may orbit around eachother. Zhatt 16:40, 27 September 2005 (UTC)

Technically, that's not quite correct. The star does not orbit around the planet, nor does the planet orbit around the star. In reality, both the planet and the star orbit around the center of mass of the planetary system. In practice, however, the mass of the star is almost always many many orders of magnitude larger than the mass of the planet, so that the center of mass of the planetary system very nearly coincides with the center of mass of the star. So as a practical matter, the planet revolves around the star, not vice versa.

As an example, in our own solar system, the Sun makes up 99.85 percent of the total mass of the solar system, and Jupiter accounts for another 0.10 percent. The remaining eight planets account for only 0.04 percent combined, and comets, asteroids, and dust account for the balance. Source: Abell, Morrison, and Wolff, Exploration of the Universe, fifth edition (Saunders College Publishing, 1987), p. 234.

In a binary system, the two stars may have masses of similar order of magnitude, so that it is correct to say that each star orbits around the other, or more accurately, each star orbits around their common center of mass.

-- Metacomet 05:49, 30 December 2005 (UTC)

I agree that the article name is wrong though. Much of the focus is on satellite orbits; the common theme is gravitational orbits. Orbit (gravitational) is my suggestion. Joffan 23:25, 17 July 2006 (UTC)

I suggest either Orbit (astronomy) or Orbit (physics). The Land 00:10, 18 July 2006 (UTC)

you guys never sorted this out, but a name change is needed here.. what are we supposed to do with articles like Satellite orbit? it apparently doesn't fall under this one.. Mlm42 14:30, 4 October 2006 (UTC)

[edit] Example calculations

This section has been moved temporarily to another location while it is under development. -- Metacomet 05:51, 31 December 2005 (UTC)

[edit] Table of orbital data

This section has been moved temporarily to another location while it is under development. -- Metacomet 05:51, 31 December 2005 (UTC)

[edit] Stability of planetary orbits

My understanding is that the stability of planetary orbits, being an n-body problem, is a open question. Wasn't there a prize offered for solving this that was never claimed? --Michael C. Price ^talk 19:50, 22 September 2006 (UTC)

[edit] Understanding Orbits Sections

In the Understanding Orbits section I've described a "range of" parabolic and hyperbolic orbits.

Is that accurate?

Or -- from a given firing height, with a given mass -- is there:

• only one possible parabolic orbit and a range of possible hyperbolic orbits, or,
• a range of possible parabolic orbits and only one possible hyperbolic orbit, or,
• only one possible parabolic orbit and one possible hyperbolic orbit?

Note both a parallel firing direction, and the "tilted cannon" discussed in the next Talk subject.

[edit] Tilted Cannon?

I'm wondering what happens when the cannon is tilted up or down (is not fired parallel to a tangent touching the surface of the Earth).

Is it never possible to launch a circular orbit at an angle like this -- or will gravity correct the path to a circle, due to the speed and mass of the object?

Is is possible to launch any circumnavigating (elliptical) orbit at an angle, or will the curve always hit the Earth?

Does such a tilt influence what the escape velocity is for the object, and the parabolic vs. hyperbolic infinite orbit shape?