# Tagged Questions

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### Testing the accuracy of a solar system simulation

I've written a java program to model the solar system, and I need to test its accuracy. What would be some good ways to do that? I've checked for conservation of energy and angular momentum. I'm using ...
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### Orbital but stationary motion

Is there a place between the Moon and Earth where an object can rest freely and revolve with the Moon? What is that called?
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### Angular Momentum and Kepler's Second Law

Let me preface by saying that I get the gist of the conservation of angular momentum, at least qualitatively. To better illustrate my question, I will consider the case of a planet orbiting a star. ...
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### Remotely finding the mass of a satellite

I have a question similar to one I've asked earlier (Calculating mass of an orbiting body with force and acceleration), but without a specific formula... How can you find the mass of a satellite body ...
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### No energy consumed in planetary motion? [closed]

Most of the orbits of planet are elliptical. How is it then that no energy is consumed?
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### Elliptical orbit changing as a star's mass increases

I'm studying Kepler's Laws, specifically the orbit of the Earth around the Sun. I know that if the Earth was more massive, the orbit would not be significantly affected. If the Sun was more massive, I ...
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### Maths of elliptical orbits

I have a simulation of the solar system that currently gives me circular orbits. I'm not 100% sure where I've limited my simulation to this, but probably it starts when I use $$v=\frac{2 \pi r}{T}$$ ...
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### How “large” is a Lagrange point?

When placing an object at a L-point, the natural assumption, as with all things gravity, is that you needn't place it in an exact spot to achieve a stable configuration. How much room do you have to ...
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### Which ellipse does the Earth's semi-major axis refer to?

In Wikipedia the semimajor axis of the earth is reported to nine digits of accuracy (nearest kilometer), and the eccentricity to eight. But to which ellipse exactly does that apply? Sun-at-the-focus? ...
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### Planetary alignment of the gas giants?

There is this nice and new applet of the orbits of the planets around the sun: Solar System Orrery You can click and drag any planet and watch their relative orbits evolve in time. I was curious ...
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### Orbit of the Earth

The question I have really is in a few parts. First what if anything could cause the orbit of the Earth to start to diminish start to go towards the Sun closer on each revolution? ( edit to remove ...
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### How does the Pluto-Charon orbital 'dance' affect Pluto's elliptical orbit around the Sun?

Like many Scientists (and people in general), I have been watching the New Horizons mission results with great interest. One aspect in particular caught my attention - the Pluto-Charon orbital 'dance'...
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### Observations of erratic rotation of asteroids

An asteroid generally has an irregular shape, therefore, one would expect its rotation is quite erratic in some sense. Are there any observational examples?
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### Why are almost every planet or star rotating? [duplicate]

Is there any simple reason? Why is spinning so common?
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### Anomalous orbit of pluto [duplicate]

Can anyone explain, why, like unlike all planets, Pluto does not have a regular orbit? Why does it have an orbit that meets the orbit of Neptune? Why does it never collides with Neptune? Is it ...
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### Gravity between Moon and Earth [duplicate]

It's known that the greater the mass the stronger its gravitational force. Hence, Sun's gravity is definitely stronger than Earth's. So the question arises that why does the Moon orbit around the ...
I'm trying to derive the (circular) orbital velocity for a given height from the center of mass of a body, like Earth. First I used the equation of the circle $x^2 + y^2 = r^2$ to get \$y = \pm \sqrt{...