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1
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2answers
70 views

How has the world remained in balance?

In the center of our galaxy, there is a Supermassive black hole. We were told in early astronomy units of school that black holes are giant vacuums that will absorb/consume the area around it. My ...
13
votes
4answers
7k views

Can the Earth leave orbit if the population of humans and other live forms increases?

I don't know a lot about physics, but this seemed like the correct place to ask my question. I apologize in advance if it is a ridiculous one. It's actually a two part question: If the population ...
1
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0answers
21 views

Topic on relativistic celestial mechanics [closed]

I have to do a small 10-15 minutes presentation about celestial mechanics, and I am searching for a topic. As a mathematician my background in physics is not very extensive, but I have some notions ...
0
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4answers
65 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 ...
0
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0answers
18 views

How to calculate angle between two objects in orbit

So I have 2 objects in orbit around the same body, and I have all the orbital elements associated with each body. How do I calculate the angle between them both or figure out when they are a certain ...
1
vote
1answer
79 views
+50

Relation between eccentric and true anomalies

If $v$ is the true anomaly and $E$ the eccentric anomaly, how can I show that $$\frac{dv}{dE}=\frac{b}{r}=\frac{\sin v}{\sin E}~?$$
0
votes
1answer
54 views

Why do the stars in a binary system, revolve diametrically opposite to each other?

I encountered this question, as I was reading up on Gravity. The author of my textbook says that the stars orbit a common centre which is their center of mass. I somehow think that this fact might ...
1
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0answers
22 views

Laplace's method to determine orbits

I am trying to do the second problem by Laplace's method, it is in spanish but the only thing that matters are the asteroid's observations and the coordinates of Earth ...
1
vote
1answer
52 views

Can a planet's orbit around a star be simulated? [closed]

Say I know all parameters like density, size, rotational velocity of a planet, could I predict its orbit around a star where I also know parameters of it? I want to design a simple model of the solar ...
1
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3answers
87 views

How to predict the location of a planet at a given time? [closed]

I am trying to create a simple two-dimensional computer simulation of a planetary system. While I've been able to understand Kepler's Laws of Planetary Motion, I do not know enough about the formulas ...
0
votes
1answer
47 views

Gravitational potential of planets

How do you work out the gravitational potential of planets in the solar system? Do orbiting planets have gpe? And what would it be relative to? The equation I know for it is mgh. But what would the ...
0
votes
2answers
105 views

Orbital mechanics: will a satellite crash?

For a satellite given an initial speed and position above a planet, I'd like to know whether it will experience an elliptical, circular, parabolic or hyperbolic trajectory, or crash into the planet. ...
1
vote
0answers
36 views

Model of the solar system orbital periods [closed]

I've written a program to model the solar system. I am now testing its accuracy. I've checked conservation of angular momentum, and it is perfectly conserved. I've also plotted the path of the ...
2
votes
1answer
51 views

The source of work by gravity force [duplicate]

I learn that any work needs a source of energy, the work of gravity force (like keeping the Moon in the orbit by the Earth gravity force) comes from where? Can we find any mass reduction (transform ...
1
vote
1answer
26 views

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 ...
0
votes
1answer
44 views

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?
1
vote
1answer
51 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. ...
0
votes
2answers
40 views

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 ...
-1
votes
2answers
62 views

No energy consumed in planetary motion? [closed]

Most of the orbits of planet are elliptical. How is it then that no energy is consumed?
6
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3answers
97 views

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 ...
0
votes
2answers
61 views

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 $$v=\frac{2 \pi r}{T}$$ ...
0
votes
1answer
32 views

Find the velocity of three planets about their centre of mass

Just wanted to check if I've done this right, because it isn't working. Mercury: mass $$3.285 \times 10^23\ \mathrm{kg}$$ position: $57,910,000,000\ \mathrm{m}$ from sun Earth: mass $$5.972 \times ...
0
votes
0answers
43 views

3-body system centre of mass

I have a three body system of point masses that represent mercury, earth and the sun. I want them to orbit about a common centre of mass, but I think the centre of mass will move. I need the centre of ...
1
vote
2answers
67 views

Calculating speed of satellite in vacuum?

Satellite speed is $35\ \mathrm{km/s}$ after burn for $500\ \mathrm{ sec}$ and after some days or months this speed is reduced automatically $34$, $33$, $32$ respectively. Questions: How the ...
0
votes
3answers
153 views

What would become of the earth's orbit if half of the sun's mass were suddenly to disappear? [closed]

I shall assume that the sun is at rest, so before the half mass disappear, the orbit of earth is an ellipse.
-3
votes
1answer
57 views
1
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0answers
50 views

Questions related to Lagrange points

For me, these two graphs are inherently different. The first graph portrays a "forbidden region" which is completely filled in, the other shows a collection of curves. Whats the difference here? ...
1
vote
1answer
39 views

Minimum energy required to remove the satellite from its orbit to infinity?

My book says that minimum energy required to remove the satellite from its orbit is equal to its total energy (K.E+P.E). But shouldn't it equal to only the potential energy difference of satellite in ...
1
vote
2answers
64 views

Does the International Space Station always travels in the same path?

From the 3d visualization http://www.satflare.com/track.asp?q=25544#TOP (the right image with the red line indication the path of the ISS) it looks like always the ISS takes the same path. Is it the ...
1
vote
0answers
29 views

What is exactly gravitational potential energy and explain P.E. $= -GMm/r$? [duplicate]

I was studying gravity and I came to know about $P.E.= -\frac{GMm}{r}$ which is derived by $GMm(\frac{1}{\infty} - \frac{1}{r})$ which the work done by the body to displace it from infinity to $r$. ...
3
votes
3answers
112 views

What is the distance between two objects in space as a function of time, considering only the force of gravity? [duplicate]

What is the distance between two objects in space as a function of time, considering only the force of gravity? To be specific, there are no other objects to be considered and the objects in question ...
0
votes
1answer
51 views

Why does Goldstein's derivation of orbits from Newton's law not yield the orbit consisting of symmetric oscillation along a line thru center of Sun?

Why does Goldstein's derivation of Keplerian orbits from Newton's law of gravity not yield the orbit consisting of symmetric oscillation along a line passing thru the center of the Sun? The fact that ...
0
votes
0answers
43 views

Finding position with respect to time along a trajectory across a sphere (orbital mechanics)

When trying to find an object's position with respect to time on a ballistic trajectory along a curved surface, what equation should I use? I know that when adding force to an object to achieve ...
1
vote
0answers
17 views

Can we use the planets and Sun to fling out a craft at relativistic speeds? [duplicate]

E.g. The Voyager crafts took various assists from the planets. Sun being much more massive, wouldn't a spacecraft gain much more energy from such a flyby on the correct trajectory? If so then what ...
2
votes
3answers
103 views

(How) can we determine mid-point on Earth's orbit?

The eccentricity of earth's orbit varies with time, but at present time its eccentricity is roughly mean e (0.0167). The position of equinoxes is far more complicated than I thought and it is not at ...
2
votes
1answer
30 views

Acceleration in an elliptical binary system

So I'm having a bit of a problem dealing with binary systems. I'm looking at acceleration in a stellar system and am not sure where to begin. Assuming both stars are of equal masses, they'd be ...
-1
votes
2answers
51 views

Why does using the modified Kepler's 3rd law and using the gravitational parameter yields different results?

$p^2=\frac{2\pi a^3}{\mu}$ ($p$ is the orbital period in seconds) gives slightly different result from $p^2=\frac{4\pi^2}{GM_1}a^3$.
1
vote
1answer
43 views

Units in gravitational N-body simulations

I use a code in Python to simulate a binary system interacting through gravity. You can find it here; The code works fine. I am however having problems with the units of length and velocity. I ...
9
votes
3answers
2k views

What happens if you slow down a moon?

Let's say you'd put a whooping big rocket engine on the surface of the moon, and slow down its orbital velocity. Not to a complete stop, mind you. Just a bit slower than it was going before (a couple ...
1
vote
1answer
74 views

How do I calculate the effect of a prograde, retrograde, radial and anti-radial burn on the orbital elements of a two-dimensional orbit?

My relevant knowledge: This question works in two dimensions, with a two-body problem (see bottom for context). To my understanding, a two-dimensional orbit has the following orbital elements (3D ...
-1
votes
2answers
90 views

Calculate the Earth’s velocity in its orbit (assumed to be circular) around the Sun [closed]

Data: GM of the Sun: $\text{GM} = 1.327 \times 10^{20} \;\mathrm{m^3 s^{-2}}$ Radius of the Earth’s orbit: $r_{Earth} = 1.496 \times 10^{11} \;\mathrm{m}$ Orbital period of a planet in seconds: $T = ...
1
vote
1answer
43 views

Can a natural satellite have a synchronous orbit?

I was thinking about space-elevators and large masses being put into geosynchronous orbit, when I considered the possibility of a natural satellite being in a synchronous orbit. I did a little digging ...
2
votes
2answers
110 views

Gravitational Null Point between Earth and Moon

I need help finding the gravitational null point point between the Earth and the Moon, the point beyond which you start falling towards Moon. I am having difficulty in taking into account the orbiting ...
1
vote
2answers
53 views

Confusion about proportionality in Kepler's 3rd law of planetary motion

I was reading about Kepler's third law on planetary motion and came across in two books $R^3\propto T^2$ and in the other $T^2\propto R^3$. So, I asked the following question on Math.SE. If both mean ...
2
votes
1answer
58 views

Why does Moon always poses the same face towards Earth?

If both Earth and Moon are rotating as well as revolving around some focus, shouldn't they have drifted out of phase with each other long ago? So, why do we always see the same side always?
0
votes
1answer
83 views

Is Voyager 2 slowing down?

Voyager 2 will leave the dominating gravitational influence of the Sun for a region where other stars have comparable influence on the craft. By the time it gets that far away, how much will it have ...
14
votes
3answers
3k views

Why do we launch rockets during the day?

The clips that I have seen of rockets launching all seem to be carried out during daytime. However, we learnt at school that rockets are fired closer to the equator and towards the east to take ...
1
vote
1answer
73 views

Can 4 collinear planets exist?

Imagine 4 planets, A has moon a and B has moon b. A and B are binary planets. Is it possible that a and b and A + B all have same the period, so that the 4 planets are collinear?
15
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2answers
348 views

Was Leverrier-Adams prediction of Neptune a lucky coincidence?

According to historians both Adams and Leverrier used Bode's law to guess the distance to Neptune, which led to a vast overestimation of its orbital period (Adams - 227 years, Le Verrier - 218 years, ...