# Questions tagged [celestial-mechanics]

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### Angular momentum for planet is constant [closed]

In this excersie we look at the system of the dwarf star Gliese 536. Gliese 536 is 10 Parsec away and has half the mass of the sun. (I guess, they mean our sun). There are hints, that there a so ...
1answer
71 views

### Orbit of stars in a galaxy

Do all stars orbit around the galactic center? If yes what makes them orbit around the center , what object creates such a massive force which makes stars millions of light years far away from the ...
0answers
83 views

### Stability of solar system

As far as I understand, the stability of the Solar system means that planets do not collide and will not in near future. The only thing that is stated on Wikipedia is that scientists are concerned ...
1answer
98 views

### Upper limit of gravity

Now I don't mean maximum gravity because there is no maximum gravity. What I mean is what is the escape distance? In other words, how far would I have to be from a mass to get away from its gravity? ...
0answers
31 views

### Gravity assisting [duplicate]

I watched Passengers movie yesterday. There was one detail which stroke my eye. Does it really make sense to use gravity assisting for interstellar travel? I'd imagine that the spaceship would have ...
1answer
122 views

### Gravitational $n$-body problem with tidal forces

This year I'm working on modelling the gravitational $n$-body problem using Newton's law of gravity where I assume that for large enough distances, planetary bodies can be modelled as point masses. ...
4answers
82 views

### Do planets on other star systems form ellipse orbits like in our solar system?

In solar system we have all planets roughly on the same plane. Is it true for all of the star systems (or at least for those that we have observed so far) with multiple planets in our galaxy/other ...
1answer
93 views

### Shape of planetary orbits

What makes Venus' orbit almost circular, though mercury's is highly elliptical,even though it is closer to sun ? Further, Why is mercury's orbit most elliptical right after Pluto ?
2answers
692 views

### Motion of planets: inverse square law

If a body is acted on by a force which obeys the inverse square law, will it mean the body follows an ellipse, if so, equating Newton's law of universal gravitation $(f=(GMm/(r^2)))$ to centripetal ...
1answer
191 views

### Voyager Speed After Launch

I am learning about gravity assist. Therefore I am interested in the flight of voyager 2. i found this diagram from Wikipedia and I have trouble understanding the massive acceleration of voyager after ...
0answers
417 views

### Proof of unsolvability of $n$-body problem for $n\geqslant 3$ in general

We know there are general solutions for 1-body problem and 2-body problem and also we know in some "special cases" there are some possible solutions for $n$-body problem for $n \geqslant 3$ and there ...
1answer
163 views

### Gravity assist, Coordinate system transformation

I am currently learning about the physics and the mathmatics behind gravity assist. I have a question regarding the coordinate transformation between the planet frame and the sun frame. I want to ...
1answer
121 views

1answer
53 views

### Another Solar System and its physics

Stick with me on this one, This is purely fictional, and curiosity. Say we travel to another solar system we know nothing about. We land on another habitable planet. We don't know the mass of any ...
1answer
3k views

### If two stars of mass $M$ and $2M$ move about their common centre of mass, then they have same angular velocity [duplicate]

Two stars of masses $M$ and $2M$ move in circular motion about their common centre of mass. Which of the following statements is true? A. Both stars move with the same radius. B. Both ...
1answer
72 views

### Is it possible to find the mass of a planet and its moon from only their diameter and the distance between them?

For example, a planet has a diameter of 200,000 km and its moon has a diameter of 20,000 km, the distance between them is 100,000 km. Would it be possible to find their masses?
0answers
34 views

### Translationally invariant speed distribution

During impact events, asteroids et al strike Earth at high relative speed, in part because objects in space move in random directions with no preferred reference frame with respect to which objects ...
1answer
874 views

### Calculating Centripetal Acceleration of Sun about Galaxy [closed]

This is a question from my Mechanics book: Calculate the centripetal acceleration relative to the acceleration due to gravity of: c) the Sun in its rotation about the center of the galaxy (the ...
0answers
157 views

### Why is our solar systems co-planar? [duplicate]

Even though moon and satellite orbit the planets in multiple planes why our solar system is co-planar? Not only that, ring systems of several planets are also co-planar. Is it the way they evolved ...
2answers
46 views

### Why do the Lagrange points lie only on the orbital plane of the two co-rotating bodies?

I could not find a detailed explanation of the fact that Lagrange points lie only on the orbital plane of the 2 co-rotating bodies. As per the wikipedia page calculations are here. There is no ...
1answer
81 views

### What is the minimum possible size for an asteroid to be able to alter Earth's orbit? [closed]

Obviously, the question as posed in the title is very incomplete. Allow me to rephrase it in more specific terms: What are the minimum possible "combined parameters" (velocity, mass, angle of ...
1answer
127 views

### Velocity in different time frames

A satellite orbiting the earth experiences time faster than a person on earth as its in a weaker gravitational field (which has a greater effect than the slowing down of time caused by its motion) ...
2answers
776 views

### Retrograde motion explanation

When taking a heliocentric model and following both Earth and Mars' orbits, Mars is in retrograde motion with respect to Earth only in the short period during which Earth is overtaking Mars. Why doesn'...
2answers
141 views

### Throwing a stone from satellite toward a planet

If I'm in a satellite which is moving in circular orbit of radius $r$ around a planet which has no atmosphere, means no air friction. And if I throw a stone from satellite toward planet then it's ...
0answers
49 views

### 2D N-BODY SOFTWARE

When I had a Mac back at JPL in the 80's, I had software that allowed me to enter the mass and X, Y velocity vectors for a number of bodies. It was fun to play with. Is there anything like that out ...
1answer
539 views

### Form of acceleration for motion in an ellipse [closed]

I came across the following question: The coordinates of a particle moving in a plane are given by $x(t)=a\cos(pt)$ and $y(t)=b\sin(pt)$, where $a>b$ and $a$ and $b$ are positive constants of ...
1answer
431 views

### Orbital mechanics : finding eccentricity and semi-major axis

i have a problem. we have a elliptical orbit. Velocities of perigee point and apogee point is given. I have to find the eccentricity and semi major axis. I found eccentricty with conservation of ...
3answers
267 views

### Would it be possible to pull Mars and Earth closer each other?

The burden of travelling between Mars and Earth comes from the distance. If the planets were closer, life could spread to Mars more easily, ensuring the survival of the intelligent lifeforms. What ...
2answers
161 views

3answers
252 views

### Orbits for dummies [duplicate]

In a certain universe a perfectly spherical, uniformly dense planet is found to be in a stable orbit around a stable star. The rest of the universe is empty space with no silly stuff like dark matter. ...
1answer
60 views

### Would a celestial body in a horseshoe orbit be tidally locked to the planet?

A smaller celestial body like a moon or an asteroid can be in a horseshoe orbit around a planet. Since it might go inside the tidal lock radius (but does not stay inside it all the time), during the ...
2answers
562 views

### Which timestep should I use for a $N$-body simulation of the Solar system?

I am trying to implement a $N$-body simulation of the Solar system and I am stuck on the issue of the simulation timestep size. At first I would like to use a simple Euler stepping scheme. Knowing ...