Can a natural object assume a (I don't know the real terms) non-equatorial orbit? I'm not talking about a circumpolar orbit, I mean assume an orbit around, lets say, the 20th parallel (only up high, of course) or do they always have to cut across the parent objects middle or center of gravity?


(Boy, that was poorly articulated)

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No, the orbit must (to a first approximation) lie in a plane with the Earth at one focus of a conic (ellipse, parabola, hyperbola). This is exactly your condition of "cut across the parent object's middle or center of gravity." This means that the plane of the orbit will always cut the Earth in a great circle (ignoring the oblateness of the Earth), thus all orbits must either be in the equatorial plane or in a plane inclined to it. The 20th parallel in your example is not a great circle, its center does not coincide with the center of the Earth, so it is not an eligible plane for an orbit.

That's why when you see one of those "mission control" maps the orbit appears as a wavy curve on a world map. And since the Earth is rotating underneath the orbit (so to speak), the curve doesn't close on itself after going around 360 degrees in longitude but is slightly displaced.

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HI BigDon

There is also Halo orbits , like SOHO orbit around L1 Lagrangian point or a possible halo orbit near L2 to the Moon.

ONE LINK / http://map.gsfc.nasa.gov/m_mm/ob_techorbit1.html

An episode of Star Trek TNG had a spacecraft in what was
apparently a stationary orbit over the north pole, which just
about turned me inside out. BAD physics to the max!

The notion that bodies orbit the center of mass is so ingrained
in me that it seems completely intuitive. I can't remember a
time when I didn't know it. Certainly I knew it when I traced
John Glenn's flight in Friendship 7 around my new globe.

Everything falls toward the center of mass.

-- Jeff, in Minneapolis

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point of rockets is to explore them!" -- Kai Yeves

Certainly circumpolar and other inclined orbits are possible as long as the plane of their orbit follows a great circle route as pointed out by Celestial Mechanic.


-Veeger

No, it wasn't poorly articulated. I understand what you mean. There was already one answer, but just to make it simple, the answer is no. The center of the orbit has to be the same as the center of mass (I'm not sure that's exactly true, but I think it's close enough to be a good explanation). So suppose a satellite was orbiting around the North pole on a plane parallel to the equator. In that case, the center of the orbit would be the north pole. So the satellite would be pulled south toward the center of mass. I hope this makes sense.

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Or, to be perfectly accurate, the center of mass of the system of objects (the orbiter and the orbitee's combined center of mass - for all intents and purposes the center of mass of the earth for any man made satellite) must lie at one of the foci of an ellipse describing the orbital path of the object. Which of course for a circular orbit of any man made object means exactly what jens said.

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Well, I was going to post an answer, but it would just be what Jens said.

The shots of the Enterprise in orbit seem to show it orbiting around the upper third of the planet with respect to the ship.

If you have enough thrust, you can orbit wherever you want or even hover. That might explain the otherwise absurdity of the Enterprise falling out of space whenever the engine failed. We can't do this today because chemical engines (the only ones that produce enough thrust) can't burn for very long before all of the propellant is consumed. However, in the Star Trek world, apparently unlimited power is available for both propulsion and mundane things like preparing a meal using a replicator.

Good point, but I'm not sure these can properly be called 'orbits', since the ship will fall if not powered.

Less seriously, in addition to unobtainium, a certain notorious invisible elf is rumored to be holding the entire futures market in dilithium crystals.

Star Trek has anti-gravity, don't forget. So it need not be in orbit at all.

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"Standard orbit, Mr. Sulu."

Heard at least thirty times over the "five-year mission" of the USS
Enterprise, I think.

It is rather surprising how quickly the orbit "decayed" when the engines
conked out, considering they always appeared to be in orbits several
thousand miles up.

-- Jeff, in Minneapolis

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http://www.FreeMars.org/jeff/

"I find astronomy very interesting, but I wouldn't if I thought we
were just going to sit here and look." -- "Van Rijn"

"The other planets? Well, they just happen to be there, but the
point of rockets is to explore them!" -- Kai Yeves

An object with an uneven mass distribution might have something in a nonequatorial orbit; say, if there had been a recent Big Whack collision between a very dense body and a very rapidly spinning planet, and the dense core from the impactor was still not yet fully sunk into the planet's (former) center of mass; the orbit would be skewed slightly towards the dense core. I think.

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"If this were play'd upon a stage now, I could condemn it as an improbable fiction."
Shakespeare, Twelfth Night
"The Mayan symbol for "book" looks a lot like a triple hamburger, but I've never seen them claiming it as proof the Mayans had Big Macs." - KaiYeves
"Distance doesn’t matter much in space, where if you just start a thing off with the right kind of shove, sooner or later it will get where you want it to go." -Frederik Pohl, Mining the Oort

All non-equitorial orbits (those that are always directly over the equator) will cross the equator precisely twice during each orbit.

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