All Questions
17
questions
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Is it possible to determine if a planet can have a moon based on its mass and gravitational pull?
I'm curious, if based on what we know with Newton's law, can we determine if a random planet, knowing it's mass and gravitational pull, can hold a moon in it's orbit.
Or to phrase it another way, is ...
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0
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0
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43
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Why are the orbit of planets usually ellipses? [duplicate]
There has been a similar question about planets' orbits being ellipses but the answer circulates around how the circle is a special type of orbit which doesn't really answer my question.
Elaborate ...
- 159
-2
votes
3
answers
149
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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
0
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0
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505
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Does the formula $v = \sqrt{GM/r}$ work for elliptical planetary orbits?
Suppose we have a central mass $M$ and a smaller mass $m$ orbiting around the central mass in an ellipse:
The other point is the other focus. We know that elliptical orbits have the central mass in ...
1
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1
answer
60
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Understanding the third Kepler law [closed]
Consider a system of two masse $M$ and $m$ with $m<<M$ and the mass $m$ orbiting around $M$. Then $m$ describes a elliptic orbit with period $P$ and the third Kepler law states that:
$$\frac{P^2}...
- 183
0
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1
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259
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Orbit eccentricity and initial velocity
I was thinking about orbital velocities, and came across this question (Velocity of satellites greater than required velocity). Does the answer to this question imply that for planets going round the ...
- 141
1
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2
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5k
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How do scientists calculate the orbital period of a planet?
It is known that you can calculate the distance to a planet using parallax, but how do scientists calculate the orbital period of a planet?
(Assuming they don't know the distance and can't use Kepler'...
2
votes
2
answers
479
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What determines if an object will stay in a planet's orbit? [duplicate]
Say you threw an object 10 AU from a planet at a certain speed, would this object stay orbiting around the planet or would it shoot off into space? And does it depend of the speed the object when it ...
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3
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2
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395
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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 ...
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-5
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2
answers
156
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How do astronomers explain trajectories of planets?
I'm wondering how astronomers can explain the trajectories of planets because:
planets spin, so have angular kinetic energy. Thanks to the mass-energy relationship this means space-time curvature.
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- 19
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1
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226
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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?
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2
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320
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How deep does a gravity well need to be to remove particles from a planetary body?
I almost considered asking this question on WorldBuilding, however I wanted the brute mathematics on the subject, so please excuse the theoretical nature of this question.
I understand the basic ...
- 123
0
votes
3
answers
269
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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
1
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1
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1k
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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.
...
- 113
0
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0
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661
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Elliptical path of planets [duplicate]
Why are the planet's orbits in the form of an ellipse and what is the proof that earth moves in an elliptical path with the sun at its foci? Initially it was thought that earth moved in a circular ...
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