All Questions
13
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 ...
- 111
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
1
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1
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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
2
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2
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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 ...
- 31
0
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1
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66
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Validity of the two-body system approximation in astrophysics
I'm taking an intro course in astrophysics and studying Kepler's Laws of planetary motion - all of which are built over the assumption that we can approximate our system to one where there's only two ...
- 548
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 ...
- 131
1
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1
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82
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Why are planet's maximal/minimal angular speed ratio harmonic?
See this Wikipedia page for Harmonices Mundi, a book by Kepler (yes, he was the one to discover the three Kepler's laws). The author writes:
He found that the difference between the maximum and ...
- 1,335
-1
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1
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285
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Where does the radial velocity component come from?
Any object under the influence of a central force will have two components of velocities: Radial and rotational
I understand that the rotational velocity is there due to the centripetal force.
But ...
- 581
2
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1
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79
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What is the second $r$ in this equation for the Two Body Problem?
$$r=\frac{r^2\frac{\mathrm d\theta^2}{\mathrm dt}}{\frac{Gm_2^3}{\left(m_1+m_2\right)^2}\left(1+e\cos\theta\right)}$$
I have this equation for the radial distance of a planet from the barycenter. But ...
- 67
2
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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
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 ...
- 274
7
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3
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829
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Falling through the rotating Earth
Suppose you were standing on the rotating Earth (not necessarily Equator or the poles) and suddenly your body lost the ability to avoid effortlessly passing through solid rock.
Because the earth's ...
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