Questions tagged [planets]

For questions about any large astronomical bodies classified as planets, and their effects on their systems.

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12
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3answers
948 views

Would co-orbital planets with very similar convergent evolutionary paths be possible?

Picture, if you will, four planets sharing the exact same orbit and orbital speed, and separated by exactly same distance from each other. Each planet is the same size and roughly the same ...
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3answers
706 views

What impact is required for a visible (from Earth) ejecta plume on Earth's Moon, and would the Moon survive?

Take the Earth-Moon system as we know it. Now, something causes a large rock to be lobbed in the direction of our moon. Exactly how that happens is deliberately left unspecified; it could be ...
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5answers
453 views

What are the day and night fluctuations for a moon orbiting a planet the size of Jupiter?

In a nutshell, I'm trying to build a world with erratic day/night cycles. To get the erratic days, I'm working with a habitable moon. It takes 3 full earth days (72 hours) for the habitable moon to ...
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2answers
912 views

I'm building a fantasy world like Earth but it has two moons adjacent to each other in a co-orbital configuration and need help

I am looking for help on the following: Will that have any affect on the length of days and nights? Would having two moons create a higher body of water on the planet due to increased tides? (i.e. ...
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2answers
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Tidally locked gas giant moon - brightness of the gas giant

Imagine a tidally locked gas giant moon, which is otherwise earth-like. One side of the moon will have a huge planet constantly hovering in the sky (24 hour day/night cycle with a Jupiter-sized ...
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2answers
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Creating a realistic world(s) map - planetary systems

Once the geography of the world is designed, it needs a planetary system to inhabit. But how should that solar system look? The only constraint is that the system needs the new world to be placed in a ...
36
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5answers
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Can a planet realistically have multiple suns?

Several science fiction books I have read (including, IINM, Nightfall by Asimov) have featured planets with several suns. Some worlds where this happened wrought interesting effects on the inhabitants ...
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4answers
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Is a Jupiter-sized planet plausible in a habitable zone?

We lived through loads of questions regarding aquatic races, so buckle up, I am going to gather some ideas around insectoids. The homeworld and race This race lives on a planet which has lower ...
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7answers
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What can we do to Mars to give it a survivable atmosphere?

Some science-fiction books I've read (including more than a few by Ray Bradbury) have men from Earth living on Mars, walking around outside of enclosures. I know that this is currently not realistic, ...
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3answers
9k views

What is the minimum planetary mass to hold an atmosphere over geologic time scales?

I realize that many factors affect this answer so assume the following: Star type: G2 star (like our Sun) Composition: O2, N2, CO2, H2O atmosphere Magnetic field: Two different magnetic field ...
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15answers
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Is it possible to build a bridge between planets?

What I am proposing is a bridge making it possible to travel between two planets, I have some ideas but I would like to know if and how it would work. Maybe somehow stopping their orbit and locking ...
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3answers
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Apparent Color of the Sun and Sky

The game Rodina features four planets, all with different colored skies. For some reason, the sun is a different color from each planet's surface (use this guide for reference). The four planets, in ...
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7answers
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5km artificial planet, with same gravity as on Earth

So, the idea in a story is that in far far future there’s a trend that rich people, they are able to buy themselves planets. Tiny little planets with sizes 4-6 km (3-4 miles) in diameter. The company ...
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9answers
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Is a moon inside a hollow Earth possible?

The Hollow Earth theory is/was a pseudoscientific idea that our world is actually on the inside of a large sphere. The "sky" points inward towards the center, where the "Sun" (a light source) is, ...
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3answers
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In a created planetary system, how many planets can fit in the goldilocks zone with stable orbits?

Given ideal circumstances and a type 4 or 5 Kardashev scale level of technology to set the system in motion (but not to maintain the motion over time): How many planets 1/4 of the Earth's mass could ...
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10answers
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What would make a sky appear purple during the day?

I'm thinking of making a world where the sky is purple, or at least perceived as purple by the native species taking centre stage in my story. What gases could cause this colour? Could the colour ...
9
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4answers
802 views

No sunlight, just high-energy radiation?

Is it possible for a planet to have very little visible-light energy and receive enough energy to support life from ionising radiation? Dim light, including starlight and ionized-air glow is ...
27
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14answers
6k views

A planet with changing gravity?

A planet with changing gravity On earth gravity stays constant (besides negligible fluctuations), but it may be possible to change that. What kind of geology, natural satellite, or other anomaly ...
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8answers
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Equatorial icecaps and polar jungles a fantasy or reality?

I am writing a science fiction movie script and a planet idea came to me a few weeks ago: A planet with equatorial icecaps and polar jungles. As interesting and intriguing as this is to think about, ...
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13answers
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How plausible is a 'tilted axis' planet with a “south pole” constantly facing toward its star?

The basic concept of this planet is that, the planet has a tilted axis (you probably guessed that already) which results in the South Pole constantly facing towards the sun. This would result in the ...
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7answers
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Could a moon have its own satellites visible from the planet it orbits?

Say you have a planet and the planet has a moon: could the moon have visible satellites as well? I don't mean a gas giant planet, I mean something habitable by humanoids or humans. Will the moon's ...
31
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2answers
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What would skies look like on Worlds inside Nebulae?

I am building a habitable Earth like planet, but instead of it being in a solar system it is inside a Nebula. The actual composition of the Nebula is uncertain at this point. I am thinking the ...
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6answers
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What could cause Earth to slowly fall out of orbit?

I would like to have Earth slowly move away from the sun, taking somewhere between several months and a couple of years to reach the point where human life on the surface is no longer possible. (The ...
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2answers
415 views

Impacts of a stellar Jupiter

In the book 2010: Odyssey Two by Arthur C. Clarke, Jupiter is turned into a star. Presumably this is done by making it more dense, so if Jupiter were to reach that density and become a star, what ...
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4answers
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Is it possible that a gas giant of similar size to Jupiter could harbor life?

Say we had a planet which was a gas giant. Is it possible that at the core of the planet where meteors, asteroids, and comet debris had collected that there could be a layer of atmosphere similar to ...
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5answers
859 views

How would the inhabitants of one planet kill the inhabitants of the other?

Two planets rotate each other and are tidally locked. They are where earth is around a star nearly identical to the sun. One planet is much wetter, featuring oceans, swamps, jungles, and forests. The ...
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5answers
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How would the sudden destruction of Earth affect other planets within the Solar System?

Earth is destroyed in explosive fashion by an unknown force. How does this affect the rest of the Solar System? Does sudden absence of that mass affect the orbits of the other planets at all? Let's ...
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6answers
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Is it possible to have a planet that has seasons and is also cold at the equator and hot both poles?

I am trying to create a planet for a fantasy role-playing game where the equator is an impassible region of ice. Ideally, I want to find a science-based solution to this and not have to resort to ...
8
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2answers
817 views

What would the conditions on a methane world be like?

The picture above is a representation of a Methane Earth. I pulled it from this Wikipedia article on alternative solvents. Several questions deal with whether life would be possible on a world with ...
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5answers
361 views

Removing an atmosphere from a previously-habitable world

Alien AI DoomFleet has a mission: Destroy threats to their creator. They do this by detecting the signature of FTL drives, going to the system, and blowing everything up, up to and including the ...
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1answer
368 views

Can I have a planetary liquid or gas ring system?

My space colonists have found a home in the ring system of a (maybe chthonian) gas giant. The rings are based on Saturn's in terms of appearance, but can they be made of gases or liquid (maybe ...
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3answers
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Is it possible to have a non tidally locked moon?

Fo my question, I'd like the moon to orbit around a saturn-like planet without rings. This moon would be located at a million kilometers away the host planet. the moon's size would be about 12 000 ...
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3answers
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What Color Can the Sky Be?

A good friend of mine, who's a doctor, is very well traveled, and he told me he's seen skies of different worlds take all the colors of the rainbow (and the grayscale to boot). I suspect that he might ...
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2answers
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How would the sudden destruction of Mars affect Earth?

If Mars was vaporized by aliens, how would it affect us? Assume that the core of Mars exploded, sending the debris flying in all directions, and that some would pass close by, but not hit, Earth. How ...
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3answers
506 views

How could a sentient life form move an exoplanet the mass of the Earth?

Okay. I have been piecing together the elements of another story for my school PDF newspaper (we publish one to a wiki page every two days). Yesterday I asked this question on whether a second ...
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4answers
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What would a planet spinning fast enough to allow geostationary orbit near the surface look like?

From an answer to a previous question of mine: A planet spinning fast enough to allow geostationary orbit near the surface would result in odd side effects. Any object at rest on the equator would ...
24
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2answers
2k views

What is the feasibility of a floating city on Venus?

I've read that the atmosphere about 60 km from the surface of Venus is very similar to the atmosphere on earth (the oxygen/nitrogen/CO2 levels and pressures are about the same). If there was a way, to ...
12
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2answers
17k views

How much force needed to blow open a planet?

I recently asked this question about what would happen if a fusion bomb went off in the core of a planet, and the answer was relatively uninteresting. As was aptly said in my previous answer, the ...
5
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3answers
537 views

About how many planets are plausible for this binary-star system?

I have a binary system in which my world orbits one of the stars, not the pair, in the habitable zone. The stars are relatively close together (because I want the secondary one to shed significant ...
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4answers
5k views

What happens when one planet “lands” on another?

Imagine, if you will, an Earth-like planet orbiting a Sol-like star. Now imagine that, from somewhere outside the solar system, a rogue planet, rocky and of roughly the same size and mass of the ...
27
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4answers
4k views

A planet illuminated by a black hole?

Is it possible for a planet to be heated and illuminated by a black hole due to Hawking radiation at the same intensity as by a star? What mass and size should a black hole have to produce the same ...
21
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3answers
2k views

Realistic sky of an Earth-like moon orbiting a gas giant (length of day and size of celestial bodies)

I'm trying to work out what the sky looks like on an Earth-like moon, in particular the length of day and apparent size of the other celestial bodies: the gas giant's size, the gas giant's other moon'...
21
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3answers
679 views

Circulation patterns on a tidally-locked binary planet

A targeted hard-science spin-off from this question: In a tidally-locked planet that rotates about a barycentric point that’s located outside of its own sphere, what would the coriolis forces be like?...
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4answers
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By what mechanism could a planet be locked into permanent solar eclipse?

I've got an image in my head of a world where it's just normal that the star is black with a golden halo around it - in other words, where the planet is in a state of perpetual solar eclipse. Are ...
11
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4answers
2k views

A world with a moon orbiting much closer than ours

The world I am envisioning is a rocky planet with oceans, plate tectonics, atmosphere, and several other similarities to our globe. The mass and size is roughly equal, but its moon is orbiting much ...
11
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8answers
888 views

Smallest possible habitable planet? (also taking density into account)

I have seen a few similar questions but none seem to take the density of a planet into account. I'm creating a planet on which several small civilisations develop. The planet needs to have a few ...
11
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1answer
896 views

What would animal life on a methane world look like and how would it evolve?

Linked: What would conditions on a methane world be like? Question: As mentioned in the linked question, Titan is the second most likely world in the Solar System to harbor life. One of the answers ...
8
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5answers
908 views

A more alien world: Flora

In the (relatively new) Star Trek movie Into Darkness, we see Dr. Bones and Captain Kirk in a world composed mainly of red plants. Obviously these are just eye candy with no real basis behind it, but ...
8
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1answer
397 views

Multi-planar planetary rings

According to this Reddit conversation, the detritus around a planet tends to form into a single plane located around the equator given enough time. How long does this process take? Suppose a planet ...
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5answers
3k views

Can I significantly shorten the days on a planet that can support human life?

I would like to have a world on which humans can live unaided -- they can breathe, the climate is workable, they can eat the local vegetation, etc -- but on which a complete day is substantially ...