Celestial body that orbits following an elliptical path around a star or stellar remnant.

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16 views

Calculating collapse factor in the crater equation [duplicate]

In the Crater Equation $$ D=0.07C_f\left(\frac{g_e}{g}\right)^{1/6}\left(E \frac{\rho_a}{\rho_t}\right)^{1/3.4} $$ where $\rho_a$ is the density of the impactor, $\rho_t$ that of the object, $g_e$ ...
12
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2answers
287 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, ...
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1answer
57 views

Why do Uranus and Venus rotate from East to west?

Why do only Uranus and Venus rotate from East to west, while others rotate in opposite direction? Is it because of the angle of their tiltness? Or due to the process of their formation?
1
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0answers
18 views

Eccentricity of planetary orbits: What information is contained?

I'm having a little trouble understanding what makes a planetary orbit explicitly elliptical. Is it simply that the initial velocity was different from the circular orbit case for a given starting ...
3
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0answers
69 views

Would a rocky planet orbiting so close to a very hot star eventually vaporize?

I was thinking about the physics behind a hypothetical scenario where a planet the size and the mass of the Earth is orbiting so close to a very hot star and what the long-term fate of such a planet ...
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3answers
139 views

Is the Earth round?

Imagine you are a common man and want to prove that the Earth is Round, how would you prove it without any mathematical derivation or without the theory of the ships.
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0answers
54 views

Why value of $g$ is 0 at the centre of the Earth? [duplicate]

My question is simple, why the value of $g$ is 0 at the core of the earth? Being the device for attracting all the objects over earth, why the value becomes nullified over itself? It should be maximum ...
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2answers
1k views

What planets are visible to the naked eye from Mars?

Here on Earth we are blessed with being able to see some other planets, Mars & Venus etc, with the naked eye on a fairly regular basis thanks to the distance between the planets. What about from ...
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2answers
3k views

Artificial planetary magnetic field

I wonder how difficult it is to create an artificial planetary magnetic field with generators? What power they would need? The question is inspired by thinking about possible colonization of ...
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0answers
52 views

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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0answers
19 views

What would happen to a planet at the heliosphere's termination shock?

Assuming that a planet with an atmosphere already existed which orbits at the radius of the termination shock of a star, what would happen to it over time? As a follow-up, would it be possible for a ...
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0answers
67 views

Has New Horizons' visit to Pluto taught us anything deeper than mere… facts?

There's a lot of interesting stuff coming from New Horizons about Pluto, but are we actually gaining any non-trivial scientific understanding from it, or is it all just "oh neat, Pluto has mountains ...
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2answers
61 views

Calculate volume of a crater

Is there an equation I can use to determine the volume of a crater in my 'drop the ball on sand' experiment? I looked at the equations for volume of hemisphere and cone but do not seem to fit the ...
0
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3answers
66 views

What is the definition of potential energy? [duplicate]

I have problems with this equation: $$U_G ~=~ G\frac{m_1m_2}{r}.$$ It's for potential energy of say something placed on Earth. But it intrigues me. $r$ is the distance from the very center of the ...
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0answers
8 views

Region of resonance and overlap

In planetary dynamics what does a region of resonance (mean motion) between two bodies mean and how to quantify the region? How does resonance overlap occur and what are its consequences? What is ...
3
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1answer
62 views

Shoemaker-Levy 9 impact on Jupiter

When the comet Shoemaker-Levy 9 impacted with Jupiter it created a ball of fire 3000 Km high and it left a mark on the surface of the planet that was visible for weeks (source: Wikipedia). How was the ...
4
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1answer
91 views

Proportionality constant in crater equations

I have searched for equations regarding craters and I came across two of them. The first one is from this NOAO website in the level two section. There, it says that, $$ D^3\propto E $$ where $E$ is ...
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2answers
56 views

Gravity underground on the moon?

They say that gravity Decreases as we dig into the earth. But I also read that gravity increases for the first approx. 2000km of distance underground. Using this rational, could we dig about 200 to ...
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1answer
75 views

Crater equation

I found this crater equation $$ D=0.07 \cdot C_f \cdot (g_e/g)^{1/6} \cdot (W p_a/p_t)^{1/3.4} $$ on a website, where $$ \begin{align} D &= \text{Crater Diameter}\\ C_f &= \text{Crater ...
3
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0answers
84 views

Protoplanetary disks, angular momentum and prograde orbits

So you've got a protoplanetary disk and you're going to gravitate yourself some planets together. The disk is made up of the usual planetary system stuff, dust and gas and whatnot, orbiting a common ...
1
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1answer
130 views

Why are tidal forces pointing away from the Moon? [duplicate]

I am currently reading The Science of Insterstellar, which explains most things very well, but some things leave me confuzzled, which I hope to get answers to here. I am no physicist, but highly ...
1
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1answer
609 views

How easily can the Earth flip?

The recent media attention to sunspot activity (however warranted) reminds me of a question I had long ago. Given the angular momentum and the slight 'wobble' of the earth, and remembering the ...
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2answers
44 views

What conditions would allow planetary-sized objects to collide and remain intact?

I am modeling some off-the-wall scenarios to try out with a game engine. One idea is trying to make a planet where some weird catastrophic incident has creates a funny shaped planet. I'm hoping to ...
0
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1answer
72 views

Temperature of planets without atmosphere

I am wondering how come a planet without atmoshhere loses heat in space when the space around it is a vacuum. In my understanding for one object to lose heat it must have contact with another ...
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3answers
76 views

How much force does it take to move the Earth? [closed]

If you could fly and survive in space, how much force would you need to move Earth at 1 meter per second?
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1answer
1k views

Correlation between speed, distance, mass, etc between a planet and a star (or moon and planet)?

While playing around with some little scripts, generating solar systems, I started to wonder about the correlation between the different objects. Up until now, distance, mass, size and speed are ...
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6answers
5k views

If the gravity at the center of the Earth is zero, why are heavy elements like iron there?

If gravity is zero at the center of the earth, why is there a core of heavy elements, such as iron? Alternate question for the opposite hypothesis: If gravity is greatest at the center of the ...
7
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1answer
196 views

Will Neptune change Pluto's orbit some day?

My seven-year-old son loves astronomy-- so much so that we read space books before bed time. One of our books talks about Pluto's orbit crossing over Neptune's orbit and will be (or is) closer to the ...
1
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1answer
100 views

Drift of Earth's orbit?

How much has Earth drifted (inwards or outwards) from its orbit about the sun? Or has Earth has not moved at all, compared to, say, 1000 years ago? 10,000 years ago?
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1answer
42 views

Helium confined to a gravity well

It's a well known problem that Earth is slowly losing its supply of helium due to helium's ability to "bubble off" the atmosphere. All the gas giants have significant percentages of helium in their ...
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1answer
35 views

Motion of a ball in a tunnel along Earth's diameter [duplicate]

Suppose, a tunnel is made along the diameter of Earth and we drop a ball inside it. How will the ball behave? Please help me in the stand.
0
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0answers
42 views

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 ...
1
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0answers
34 views

How can a gas giant be said to have an atmosphere?

They are made of gas, right? So, there won't be a solid-gas or liquid-gas boundary that defines where the atmosphere starts. So, if there isn't a boundary, we can't define part of it to be an ...
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5answers
12k views

Would you be weightless at the center of the Earth?

If you could travel to the center of the Earth (or any planet), would you be weightless there?
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0answers
46 views

How to calculate the mass of a sun that is similar to our own

How would you calculate the mass of a sun that could host a habitable planet, with only given the values of the mass of our own sun. And the fact that it takes a specific amount of years for life to ...
15
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6answers
16k views

Why don't planets have Circular orbits?

This might be a completely wrong question, but this is bothering me since many days ago. Given the mass (Sun) curves the space around it, gravitation is the result of such curved space (Correct me if ...
1
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1answer
935 views

Atmospheric escape of gas molecules

Most of the objects in space are likely to have an atmosphere. Since space is void, the gases in atmosphere should have either dissolved or emptied into space. But, some of the objects still seem to ...
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2answers
98 views

If planet like Jupiter is massive enough to hold hydrogen with its gravity is it bound to become a star?

I have been reading about Jupiter as of late and reason I am asking is if Jupiter has strong enough gravity to pull hydrogen to itself then it should be only matter of time when it will acquire enough ...
14
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2answers
2k views

What would be the rate of acceleration from gravity in a hollow sphere?

Lets say the Earth is hollow and you are in the center of it (Same mass except all of it is on the outside like a beach ball) If you move slightly to one side now your distance is closer to that side ...
3
votes
1answer
40 views

Protoplanet formation & Kessler Syndrome

In the early stages of the solarsystem rocks clumped together randomly until their gravity drew in more material which led to protoplanet formation. But how does the dust and do the rocks form bigger ...
0
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1answer
47 views

If I observe a planet because of reflected sun-light, how does the radiant flux vary with distance?

I wish to figure out how the flux of the sun's reflected light from a planet varies with distance, so assume an observer is on the sun, looking at a planet, and the light originating from the planet ...
2
votes
2answers
58 views

Do the outer gas planets radiate their mass?

We know that the sun experiences angular momentum loss, and radiates a portion of it's mass (though helicity is conserved). Can we say the same about massive Jupiter, or even Saturn, Uranus or ...
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2answers
38 views

Planet Sized Generator

I have an interesting idea for an energy generator and I want to see what you think. Basically, you take a small planet and drill from one side to the other so it looks like a sphere intersected ...
24
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3answers
3k views

Why do the storms of Jupiter have long life unlike that of Earth?

Recently I saw How the Universe Works. In one of the episodes, concerning Jupiter, they told that the storms on Jupiter can survive many, many, times longer than those on Earth. What is the reason ...
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5answers
2k views

What would happen if I were to fall into a massive hollow planet?

Imagine, if you will, there exists somewhere out there a supermassive planet. For some reason, this planet is only a shell of its former existence and all that is left is a crust of substantial size ...
3
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0answers
52 views

Could there be a dark matter planet? [duplicate]

Since dark matter is gravitationally "charged", by which I mean it has mass and attracts things, could it bunch together to form a planet?
5
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3answers
151 views

Is the planet Mesklin as described in Hal Clement's Mission of Gravity correct?

The book Mission of Gravity describes a planet with a mass of 16 times Jupiter spinning at a rate of one revolution every 17.75 minutes. This causes it to stretch out into an oblate spheroid and has ...
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0answers
13 views

Saturn's Hexagon [duplicate]

I am currently trying to understand the formation or indeed the explanation as to why the hexagonal north polar vortex on Saturn is exactly that: Hexagonal. I understand that the most prominent ...
13
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1answer
952 views

Falling into Saturn or Jupiter, would we pass through it until we hit the nucleus?

If we fall into Saturn or Jupiter, would we pass through it until we hit the nucleus? Or would we hit the surface and stop there?
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1answer
185 views