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# Questions tagged [planets]

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

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### A planet made of iron

Our planet has a surface full of silicates and a core made of iron. It's due to this that Earth is the way it mostly is - most rocks and many minerals contain some form of silica. But what about a ...
1k views

### Could two stars of equivalent mass/size form a binary system and be different colors?

I have an idea for a planet that orbits two stars. These starsslowly orbit each other, have equivalent masses/sizes, and while one is slightly red, the other is slightly blue. When I talk about the ...
4k views

### Could there be a planet bigger than Earth, but with less gravity?

Is it possible to have a planet that is both bigger than Earth and weaker in terms of gravity? I've got an idea about it being less dense, but I don't know what to do about its magnetic field. I need ...
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### The view of the sky from an Inverted/Hollow Earth?

Obviously there are plenty of potential physics problems with this scenario, but if people lived along the inner crust of the Earth, and there was a Sun-like core at the center with nothing else in-...
741 views

### Stability of Multiple Moons

How stable (or possible) would binary moons be, (Luna-sized or possibly slightly smaller) rotating around an earth-sized planet? Edit: Thanks for the questions! And thanks for the welcome! My ...
901 views

### Is this circumbinary planet set up in a stable manner?

This is the ideal set up for my solar system: EDIT It's been pointed out that this is not a stable set up, so I want to clarify that everything in this set up can be changed at will to fit my planet. ...
428 views

### I've determined how many planets my solar system could plausibly have. How do I figure out what kind of planets they are?

The 12 planets in my solar system orbit the G-type star of Nemo. It's about nine-tenths of the size of the sun, and has a stellar luminosity of 0.67 L☉, a diameter of 1.28 million kilometres, a ...
7k views

### How to make an Earth with 27 suns work [duplicate]

Viability of Many Suns This is the first of a thread of related posts on a hypothetical alternate universe/Light Plane. Other posts from this thread are here: How To Make an Earth with 27 Suns Work,...
3k views

### Planet with dual core

My premise involves a habitable planet with a dual core: it has two masses similar in composition to Earth's core, which revolve around each other over the course of hundreds of thousands of years. ...
4k views

### What would happen to Earth if the Moon was destroyed?

In the movie Oblivion, the Moon has been destroyed by invading aliens. Several shots of the moon show what is left: If the moon was somehow shattered like this, what would the effect be on Earth?
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### What natural processes can cause a sidereal day to be significantly longer than a sidereal year?

Most of the planets that we know of have a sidereal day (rotational period) that is shorter or on the same order of magnitude as their sidereal year (orbital period), the latter being the case in ...
592 views

### What is the color of Venusian sky 50km from surface

It is said that around 50km above the surface of Venus is the most earth like environment on the whole solar system (source here), At an altitude of 50 kilometres (31 mi) above Venerian surface, ...
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### Could the moons of a Gas Giant all be habitable if that planet was in the habitable zone?

I ask this as a basis for a World (in this case Moons) Building I'm doing. I came up with a couple of different problems and some possible solutions to those problems: All of these questions presume ...
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### Sky color of an alien world

I'm asking for a world I'm making, which orbits a red star. According to this image, there is a star that would make the sky white. What would the sky look like during sunrise and sunset on a planet ...
523 views

### How much does my secondary star heat the planet orbiting my primary star?

In this question I asked about the lighting patterns from this system: A really helpful answer there explained when the planet is getting how much illumination. This question is about heat. On ...
491 views

### On the habitability of the night side of a tidally locked planet

If an Earth-like planet was tidally locked to a star similar to Sirius A, at which distance from the star would the night side be able to have liquid water, possibly with an average temperature of ...
521 views

### How Would It Feel To Walk On A Rocheworld?

A while back I saw this video talking about the habitability of double planets and Rocheworlds. I haven't seen any questions about the latter case here, so I decided to take a swing at it. For some ...
562 views

### Is life possible on a world where the water floats in the air?

Let's assume I have a planet and the planet itself is made out of something solid. Around the floating rock is a layer of gas, then a layer of liquid and then a layer of gas again. Thus the sea ...
198 views

### What are the required proportions of a moon that allow it to orbit around a planet?

The planet I'm working with has two different moons, both around the same size (3/4ths that of the main planet). Is it possible for the planet to support the orbit of these moons, especially with ...
2k views

### Fire Resistant Fauna

This question is connected to: Fire Resistant Flora I've been pondering a short story concept where a scientific expedition discovered a planet with a huge amount of both free hydrogen and oxygen in ...
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### How long would it take to terraform a lifeless but somewhat earthlike planet using bacteria, fungus, seeds and eggs?

What are realistic time-schedule expectations for far-future terraforming and developing earth-like plant and animal/fish/bird populations on distant planets, by means of robotic space probes with "...
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### What determines the length of a day on a planet?

The length of a day on different planets in the solar system varies a lot. For instance, Mars' day is about the same length as Earth, while a day on Venus is equivalent to 243 Earth days (source). ...
2k views

### Could it be possible for two planets to collide and not kill everything?

Before we begin, two things. This question was inspired by this one. I definitely don't want this to happen. So, I have two very close tidally locked planets, each fills up about 2/3 of the sky of ...
687 views

### Seasons on Infinite Cylinder Planet

An infinitely long cylinder, made of planetary matter with an average radius roughly equivalent to the average distance Earth's equator has to its center, orbits around a parallel, infinitely long ...
1k views

### Emulating a geocentric planetary system

Some published settings -- such as the Greyhawk 'verse commonly seen in conjunction with Dungeons & Dragons -- treat the prime planet's host solar system as geocentric. How could this be ...
1k views

### Single biome (hot) desert planet, possible?

I have the below snippet describing a planet in a (hard) sci-fi setting. This harsh planet has some human settlers, who can survive the climate in light weight environmental suits. The planet is a ...
3k views

### What would be the effect of a powerful explosive going off in the core of a planet?

What would happen if a powerful explosive went off in the core of a planet? On Earth, you have several layers of the planet, the crust, the magma, the outer core, and the inner core. Right now, human ...
3k views

### How to prepare for a huge asteroid strike?

The scenario is the following: a civilization with technology level similar to humanity's current, on a planet similar to Earth, shall be hit by a massive celestial body in approximately one year. ...
13k views

### Can life exist on planets like Mercury?

Can life exist on planets as barren as Mercury? How would it survive? It seems like it couldn't. Mercury is very hot, would any life break down becuase of the heat? What other challenges face life on ...
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### Could a gas giant with layer similar to Earth atmosphere exist?

Imagine a world like ours. Gravity, atmosphere, sky... just nothing solid down there. At least not anywhere close. Would it be possible? I know this is similar to this question. So to specify what I ...
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### How stable is the hexagonal rosette anyway?

The Wikipedia article on Klemperer Rosettes states that hexagonal rosettes are slightly more stable than other, non-hexagonal rosettes, due to the position of the orbital objects in the Lagrange ...
478 views

### What is the maximum orbital time for my moon around my planet?

I fear the math involved is beyond my capabilities on this one. I have what I consider to be more than a Layman's understanding of the physics involved, and I believe I can follow the math well ...
492 views

### Can this unique planet be colonized?

In the story I'm writing, a gas dwarf (named Eden) is discovered in a triple star system. Its atmosphere is mainly oxygen and water based, and its gravity is slightly higher than Earth's. Unlike our ...
908 views

### Climate on an Island World

I'm currently creating a world with a population of about 4.5 billion people and 21st century technology. In fact, the world is strikingly similar to ours. Oh, except the islands that is. The ...
916 views

### How would an intelligent race on a methane world achieve a fire equivalent?

Linked: What would the conditions on a methane world be like? What would animal life on a methane world look like and how would it evolve? Background: Okay, an intelligent race has evolved on a ...
1k views

### What Is The Minimum Size Of A Planet To Harbor Human Life?

What is the minimum size of a planet that could harbor human life? You get to decide what the atmosphere is, but I'm reasonably sure that O2, CO2, and H2O are necessary components of the atmosphere. ...
897 views

### Can a planet have 10x Earth mass, 4x Earth gravity and support intelligent life?

In the Mass Effect series there's a terrestrial planet called Dekuuna with 10 times the mass of Earth, a surface gravity of 4G and a native intelligent race. I was just wondering if it was possible ...
503 views

### Tides on a double planet

I am making a world to be the setting of my future fantasy works, which is to say I really have no story planned but I want to have a world for it when I do and I want said world to be likely give me ...
325 views

### Is a planet with a primarily reddish/pinkish sky a plausible place for humans to live on?

Assuming that the sky isn't that color because of excess pollution, would the makeup of the atmosphere need to change? And if it were breathable, would the necessary position and color of the sun ...
482 views

### Is my “flying fish” world plausible?

In the story I'm working on, a rift in space time opened up between our world and a layer of oxygen in a gas giant at some point in the past. Eons earlier, a species of fish symbiotically linked with ...
587 views

### Methods for simulating low gravity on high-g planets

There are a lot of solutions for living in low gravity environments. (e.g. centripetal acceleration, linear thrust, etc.) But what about living on high gravity planets? Is there anyway to build or ...
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### Is a spherical core and magnetic field possible in Cube world

Pretty self explanatory question...can the Cube Earth described at the link below support a spherical core and a magnetic field? How would a civilization that has been living on a "cube" ...
614 views

### Orbit of a double planet

In a system where 2 planets of similar mass are orbiting around a common barycenter, would the following configuration considered stable on the long run? They orbit at 1,6 AU from their star The star ...
832 views

### Could we move and terraform the planet Venus?

Ok, so the Earth is filling up, finite resources, and as we all know, there are no plans for us to reduce our resource hungry ways,...and Mars has no magnetosphere apparently which means we couldn't ...
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### What could cause the world to be almost completely submerged in water, naturally or man-made?

I'm trying to build a world that is almost completely water, but I couldn't come up with an explanation for WHY the world was like this. The world has the same gravity and atmosphere of Earth. It also ...
822 views

### How far could a planet be from its star and still be kept habitable by intense greenhouse gases?

Epimetheus is a planet with about three times the mass of Earth orbiting a sun-like star in the Andromeda galaxy. However, two major factors separate Epimetheus from Earth. First, it has a thick ...
4k views

### Would the atmosphere of an alien planet with the following mixture of gases be breathable to humans?

35% O2 (oxygen) 61% Ar (argon) 1.07% CO2 (carbon dioxide) 0.93% As arsenic 2% Other trace elements On an exoplanet with a mass of 0.284 Earths and a surface gravity of .66 gs (6.44 m/s^2), would this ...