Linked Questions

35 votes
6 answers
6k views

What's the smallest reasonable natural planet or moon with Earth-like surface gravity?

We all know that equation for surface gravity is $$ g = \frac{4\pi}{3} G \rho r $$ So if we want Earth-like surface gravity of $ g = 9.81 $, then the equation for radius is $$ r = \frac{3 g}{4\pi G ...
Mołot's user avatar
  • 33.3k
13 votes
6 answers
6k 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 ...
Jetscooters's user avatar
  • 2,193
15 votes
3 answers
1k views

What would the minimum mass of a water world need to be to form ice Vll, due to pressure, at its core? What about ice X, ice Xl, and higher?

I'm thinking of a planet in a Goldilocks zone similar to Earth's, with a similar atmosphere, and similar atmospheric pressure and temperature at the surface. Gravity would be variable, based on the ...
KernelOfChaos's user avatar
6 votes
4 answers
3k views

How to design a super-earth that is 80,000 km in circumference?

My question is the following: How could I design and/or justify a habitable planet that is 80,000 km in circumference? The planet should: Be habitable Have a gravity similar to earth's Have active ...
ThomasEvenor's user avatar
7 votes
3 answers
290 views

Are there any plausible 'alternative' methods of planetary formation?

The selected answer on this question provides an extremely good, and detailed, description of what is generally accepted to be the main (only?) way a terrestrial planet can form, i.e. through ...
Harthag's user avatar
  • 4,123
6 votes
4 answers
334 views

How un-dense could a super-duper-Earth be if that super-duper Earth was bigger than Neptune?

Long story short, I have an Earth-like planet, which is orbiting a mega-Earth (think a super-duper-sized version of a super-Earth), which is orbiting a K-type star, which is orbiting UY Scuti. I want ...
KEY_ABRADE's user avatar
  • 13.1k
3 votes
3 answers
669 views

How could an Earth-like planet of 1.5-2.0 Earth radii have similar gravity to Earth?

If we had an earth like planet except it had a 50 - 100 percent bigger radius than our earth what are some ways that it could have have similar gravity when compared to our own planet? P.S. ...
Christopher Void's user avatar
2 votes
2 answers
247 views

How big can a (human) habitable planet be while having around x0.7 the surface gravity of earth?

I've been working on the world-building for my setting and I realized I haven't really thought about the implications the lowered gravity I'm working with would have on the size of the planet. ...
Photografo's user avatar
3 votes
1 answer
319 views

Any potential problems with the density of a planet with a volume 8 times that of Earth but the same surface gravity as Earth?

Assuming that there is an Earth-like planet that has 8 times the volume, 2.83 times the radius, and has the same surface gravity as Earth, and has oceans; what are potential problems concerning the ...
DRY1994's user avatar
  • 77
3 votes
1 answer
282 views

Will my planet work? (size, gravity, atmosphere)

I was going to sort this all out beforehand, and then write the book, but when the writing flows... you make hay. I am a perfectionist/details-oriented person, but you lose me on math/hard science. ...
Adversary's user avatar
1 vote
0 answers
172 views

Super dense planet? [closed]

What's the most dense a planet could be and still be livable? How does water factor into the overall density of the planet. Is something like an osmium or iridium core even be possible/realistic? If ...
Dom's user avatar
  • 11
1 vote
0 answers
74 views

How big could a planet be and still have earth like conditions? [duplicate]

I am building a world that I would like to be as big as possible and still have very close to earth like conditions, gravity, weather, seasons, life and other things that are similar. Would things ...
Zurrock Wolfhart's user avatar