Celestial Mechanics is the branch of astronomy devoted to the study of the motion of the celestial bodies on the basis of the laws of gravitation.
Questions tagged [celestial-mechanics]
765 questions
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Can an atom orbit the Sun?
Is it possible for a molecule or atom to orbit a star (e.g. the Sun)? Or is there always too much outward force imparted by solar radiation compared to the inward force of gravitational attraction?
Nicole Sharp
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4 answers
How far ahead can we predict solar and lunar eclipses?
The solar system is non-integrable and has chaos.
The sun-earth-moon three-body system might be chaotic.
So, how far into the future can we predict solar eclipses and/or lunar eclipses?
How about 1 million years?
Jiang-min Zhang
- 4,262
60
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What does the Moon's orbit around the Sun look like?
I'm curious as to what the Moon's orbit around the Sun looks like. If there's an answer, what's the intuition for it? Here are some things I'm assuming when trying to tackle this question:
The Moon's orbit must be concave toward the Sun.
The Moon…
Alex
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Why are $L_4$ and $L_5$ lagrangian points stable?
This diagram from wikipedia shows the gravitational potential energy of the sun-earth two body system, and demonstrates clearly the semi-stability of the $L_1$, $L_2$, and $L_3$ lagrangian points. The blue arrows indicate lower potential energy, red…
Ehryk
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What did general relativity clarify about Mercury?
I frequently hear that Kepler, using his equations of orbital motion, could predict the orbits of all the planets to a high degree of accuracy -- except Mercury. I've heard that mercury's motion couldn't be properly predicted until general…
Carson Myers
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"Falling upward" - how far you have to be from Earth to start falling to the Moon?
Talking about gravity with my 9 y/o she asked when do we start "falling upward" to the Moon. What is the distance at which the Moon's gravitational attraction is higher than that of the Earth and thus makes you accelerate towards it, and how to get…
rafb3
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Is there a maximum distance from a planet that a moon can orbit?
Given a planet that orbits a star, and a moon that orbits that planet, is it possible to define a maximum orbital radius of that moon, beyond which the moon would no longer orbit the planet, but the star instead?
I initially (naively) thought this…
leeman
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Why are the orbits of planets in the Solar System nearly circular?
Except for Mercury, the planets in the Solar System have very small eccentricities.
Is this property special to the Solar System? Wikipedia states:
Most exoplanets with orbital periods of 20 days or less have near-circular orbits of very low…
Mark Eichenlaub
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If the 3-Body force problem hasn't been solved, how do rocket scientists plan orbits of spacecraft?
What methods would they use to predict what would happen in a situation when a probe is being acted upon by the gravity of two stars, say?
DannyH
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Gravity on the International Space Station
We created a table in my physics class which contained the strength of gravity on different planet and objects in space. At altitude 0 (Earth), the gravitational strength is 100%. On the Moon at altitude 240,000 miles, it's 0.028%. And on the…
SuperStack
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Why are there so many objects perfectly orbiting each other? Isn't it infinitely more likely that two random objects crash/fly apart?
If, in free space, I throw two objects towards each other, they can either miss each other and fly apart (if the velocity is enough and there's not enough gravitational attraction between them), or they can be attracted enough to each other that…
chausies
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For a spacecraft orbiting a planet, orbital speed is inversely proportional to orbit radius. But speed must be increased to increase orbit radius?
For a spacecraft in orbit with radius $r$ with speed $v$ around a planet, centripetal force $F_C$ is provided by gravity:
$$\frac{GmM}{r^2}=\frac{mv^2}{r},$$
which simplifies to
$$\frac{GM}{r}=v^2.$$
This means that orbits closer to the planet are…
drabus
- 383
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How do horseshoe orbits work?
An asteroid was recently discovered that is in a horseshoe orbit with respect to the earth. Is there an intuitive explanation for these orbits? It seems that the earth acts as a repulsive force where one would expect gravity to be attractive. From…
Carl Brannen
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Why is Larry Niven's Ringworld Unstable?
In his 1970 science fiction novel Ringworld, author Larry Niven describes the eponymous Ringworld, a gigantic structure shaped as a ring with a radius of around 1 AU, rotating around a star in the center of the ring. This system is described as…
Oak
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7 answers
Why does the Earth follow an elliptical trajectory rather than a parabolic one?
I was taught that when the acceleration experienced by a body is constant, that body follows a parabolic curve. This seems logical because constant acceleration means velocity that is linear and position that is quadratic. This is what I learned…
Nader Youhanna
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