All Questions
Tagged with celestial-mechanics planets
14
questions
29
votes
6
answers
14k
views
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 ...
- 53.2k
1
vote
1
answer
10k
views
What is the relationship between mass, speed and distance of a planet orbiting the sun?
After reading this fascinating story about a new exoplanet, I was wondering about how mass, speed and distance determine a circular orbit of a planet around a star.
Given the mass of the sun and star,...
- 113
10
votes
4
answers
1k
views
Collision of Phobos
Mars has two moons: Phobos and Deimos. Both are irregular and are believed to have been captured from the nearby asteroid belt.
Phobos always shows the same face to Mars because of tidal forces ...
- 1,516
9
votes
4
answers
2k
views
Binary Star system with one star stationary?
Can a Binary Star system be possible where in one star is stationary and the other star revolves around it? (Just like a planet revolving a star. i.e planets in the system and the star revolving ...
- 265
9
votes
2
answers
2k
views
Does a tidally locked planet have seasons?
Could a tidally locked planet have seasons?
According to my understanding, a tidally locked planet rotates around itself exactly once per rotation around its sun. However, if the axis of rotation of ...
- 1,125
6
votes
3
answers
1k
views
Rocky Planet in the center of System [duplicate]
We all know that mostly stars are at the center of planetary systems, but is it possible that instead of a star there was a rocky planet in the center with stars (and other planets and moons) orbiting ...
user45974
3
votes
2
answers
395
views
How Can I Calculate the Speed Required for an Orbiting Planet to Pass Through a Given Point in Space?
I've been trying to derive an equation for this for a while now, but I haven't had much success.
Let us set up the equation. There is a star with mass $M$ and a planet that is distance $d$ from the ...
- 131
2
votes
1
answer
427
views
Tidal locking of a planet to a satellite
As in the case of Pluto and its moon Charon, both the bodies are tidally locked to each other, will the Earth ever be tidally locked to the Moon? Is there any effect on the rotation of the Earth ...
- 2,754
1
vote
1
answer
1k
views
Could this planetary superalignment happen?
Here's the 'superalignment' I'm referring to:
We've all heard the stories about 'mystical planetary alignments' that will increase/decrease the effective surface gravity experienced on Earth (one ...
- 3,241
1
vote
1
answer
1k
views
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.
...
- 113
1
vote
3
answers
1k
views
Why does angular momentum being constant prove Kepler's first law?
So I was watching this video and this video on Kepler's first law in order to understand the proof of Kepler's first law. He started off by saying that for an ellipse, the distance from a focus point ...
0
votes
3
answers
269
views
Gravity effects when deleting stars or planets
In one of the latest SCIFI movies, they collect a star absorving it entirely in a kind of planet size gun/machine. As mass cannot disappear, I assume it was just concentrated inside their machine (...
- 193
-2
votes
3
answers
149
views
Why is the shape of the orbit of the Earth as it is?
My View: I think that if the sun were only force acting on earth (as a centripetal force), the earth would have a circular orbit. Since other planets also exist , there also exists gravitational force ...
- 159
-5
votes
2
answers
3k
views
Why are planets in unstable equilibrium in a stable orbit? [closed]
It is well known that a planet in stable orbit is in unstable equilibrium. If e.g. the moon was just a few m/s slower in velocity, or a few m closer to the earth than it is, the gravity would ...
