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Questions tagged [astrophysics]

For questions regarding the application of the laws of physics to orbital mechanics, stellar evolution, and other astronomical processes and celestial bodies.

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20 answers
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Killing a star safely

A messenger from the stars just arrived in peace but has brought horrible news. A vast swarm of planet devouring phototropic insects are approaching from deep space and our only hope is to obscure or ...
Henry Taylor's user avatar
  • 69.2k
43 votes
9 answers
7k views

How much damage would a cupful of neutron star matter do to the Earth?

Suppose we used SCP-261, the vending machine that produces anything, and ask for a cup of neutron star. The machine instantaneously produces this. Suppose also that the vending machine is located at ...
Quadratic Wizard's user avatar
40 votes
19 answers
11k views

Why would space fleets be aligned?

Recently I noticed how space fleets are all constructed so the ships are all aligned. With 'aligned' I mean the way how all ships seem to have a 'right way up' and that all the ships have the same ...
A Lambent Eye's user avatar
32 votes
10 answers
7k views

How can solar sailed ships be protected from space debris?

So we all know that interstellar starships that travel at high relativistic speeds, like 50% c or above, would be very susceptible to getting destroyed just by a grain of salt hitting it during travel....
Galaxy's user avatar
  • 571
30 votes
4 answers
5k 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 ...
Anixx's user avatar
  • 5,306
21 votes
9 answers
4k views

Earth is accelerated out of the solar system - do we keep the Moon?

I've been reading about stellar engines. The Wikipedia article on them says this about the acceleration they could provide to a star: Such thrust and acceleration would be very slight, but such a ...
The Square-Cube Law's user avatar
20 votes
7 answers
4k views

Can I warm up outer space?

My universe was created without stars, of any kind (which includes the sun!), and has continued that way for about 2000 years. To clarify, all life (intelligent life) was created by the deities around ...
celerysticks's user avatar
17 votes
6 answers
4k views

What elements are useful for humans, but rare in our galaxy?

I know for example there is an interesting gap in the amount of lithium, beryllium and boron compared to Helium and Carbon, but I don't know how useful they are. Here is a graph showing relative ...
speeder's user avatar
  • 716
17 votes
5 answers
3k views

Where could we add a new planet to the inner solar system?

Assume there was a super advanced alien race that for some reason, wanted to add a new planet, of lets say 1 Earth mass, into the Solar System. Where in the inner Solar System (The part of the solar ...
KaffeeByte's user avatar
  • 1,702
16 votes
13 answers
14k views

Is stealing the moon actually possible?

I'm writing a heist story set in the near future. The goal of my main protagonists is to actually steal the Moon. The budget of their escapade is not a variable; they will get this done however ...
Gideon Ebeling's user avatar
16 votes
3 answers
5k views

A 1 kilometre wide sphere of U-235 appears in an orbit around our planet. What happens?

Let's suppose that after seeing aliens get portrayed negatively in science fiction and wishing to end the discrimination, the ancient H'andh'wh'a'vians decide to destroy Earth and humanity. As they ...
MedwedianPresident's user avatar
16 votes
3 answers
5k views

What is the largest fraction of Earth's sky that an astronomical object could take up (visually) before ripping Earth or itself apart?

I know the Roche limit limits how close another planet could get to Earth. Closer than that limit, and either it breaks apart or Earth breaks apart. I don't care what size it is, if it's a super-...
cowlinator's user avatar
  • 1,839
16 votes
6 answers
2k views

Viability of a mega star system

So my story hinges largely upon a precursor type race centered around a single star system that went extinct tens of thousands of years prior to the modern day. Obviously, the most common way to go ...
Bakuhaku's user avatar
  • 223
16 votes
12 answers
652 views

What biological trait could make (certain members of) an insectoid species good at astronomy?

This is a science fiction intelligent alien biology question. I'm imagining a race of large (around 2m in height) insect-like species on a distant planet who discovered astronomy VERY late in their ...
Chaffee's user avatar
  • 1,567
14 votes
13 answers
4k views

Aliens to play a mischievous space-time practical joke on Earth

Premise Suppose an earth-like world in the near-future. Then aliens come and decide to play a mischievous trick on this world on an epic scale. The goal is to disrupt Earth's time by 18 minutes. ...
Arash Howaida's user avatar
14 votes
4 answers
3k views

Could the moon crash into the earth if we colonised it and increased its mass?

Suppose we begin to colonize the moon. Assuming the building materials and biological material are all imported (not taken on-site), would it be possible for the moon to become massive enough to fall ...
Thymine's user avatar
  • 802
14 votes
8 answers
1k views

Is it possible to have the age of the universe be unknown?

I’m making a fictional galaxy, and I want the inhabitants of this galaxy to be unable to calculate the age of the universe, I want them to be unaware of how much has already happened. I’ve already ...
Nobbe's user avatar
  • 314
14 votes
2 answers
540 views

Rogue Planet Illuminated by Galactic Centre

The black hole question reminded me of an idea I wanted to implement at some point in a space campaign, but didn't go forward with because I was unsure whether it's merely statistically very ...
vicky_molokh's user avatar
  • 1,811
14 votes
1 answer
470 views

Radiation Levels and Effects on Planet with 27 Suns

Other posts from this thread will be posted here: How to make an Earth with 27 suns work (Closed as a duplicate of the follow up, Attempt Two) How To Make an Earth with 27 Suns Work, Attempt Two: ...
FoxElemental's user avatar
  • 3,256
12 votes
12 answers
4k views

Alternate universe where life is more common; is it feasible?

Let's imagine a story where the "aliens" leave a lot of super-advanced technology somewhere in the solar system. Scientists spend years excavating this technology and while it seems too ...
Mishima's user avatar
  • 999
12 votes
5 answers
3k views

Could gravitational lensing be used to protect a spaceship from a laser?

Suppose Ship A is being targeted by Ship B, which intends to use a laser weapon in an attempt to destroy Ship A. Ship A has special technology that allows it to alter gravity (mainly used for ...
Isabella Morrigan's user avatar
12 votes
6 answers
5k views

How massive would a planet need to be to sustain negligible damage from impact with the Earth?

I'm curious what factors a terrestrial planet impacting the Earth would require for the impact to cause negligible damage to the larger planet, while destroying the Earth.
Wax's user avatar
  • 655
12 votes
5 answers
7k views

The rotation of the sun's core doubles in speed every 10 years. How many years before the situation turns apocalyptical?

I'm asking this because I'm writing a fictional story where I need a doomsday scenario that means humanity must escape the earth. The timeframe that would fit the plot of the story would be in the ...
ElectronicToothpick's user avatar
12 votes
6 answers
3k views

Do seasons occur on a tidally-locked planet?

I have done some research and so much contradict one another or I simply fail to understand. Do seasons occur on a tidally locked planet that isn't tilted on its axis?
Mister Onion's user avatar
12 votes
2 answers
866 views

Could a planet's tidal forces break an asteroid passing very close to it?

I want a certain asteroid of my system to break into pieces as it approaches a planet, having one fragment impact the planet itself, another fragment slingshot and impact the planet's moon and the ...
El Nitromante's user avatar
11 votes
4 answers
683 views

How could a galaxy be damaged by a civilization's industrial expansionism in ways that mirror our own current climate crisis?

There are several stellar environmental results from sentient industrial over-expansionism that I can imagine ie. star lifting that results in entire systems becoming frozen husks and debris from ...
Wolf Beaumont's user avatar
11 votes
1 answer
510 views

What sets of stellar models are freely available for reference when worldbuilding?

Often, when I'm building a world, I want to start out by determining some of its key properties. Maybe I'm trying to calculate a habitable zone, or figure out how long a year would be on a particular ...
HDE 226868's user avatar
  • 101k
11 votes
1 answer
305 views

How deep can the oceans be while still alowing some land?

Many alien worlds will most likely be water worlds. I was wondering what the deepest possible global ocean dept is where land is still possible. I think that volcanic islands will still have a chance ...
TheDyingOfLight's user avatar
10 votes
5 answers
1k views

Making A Geosynchronous Orbit Impossible

Here's the idea: A geosynchronous orbit is an orbit that makes sure that the orbiting satellite is always above the same spot on the planet, so its orbital period is equal to a local day there. I've ...
TysonDennis's user avatar
  • 2,380
10 votes
6 answers
2k views

How could a breathable ultra-high pressure atmosphere form?

Some background: I'm developing a world that could, theoretically, be inhabitable by humans (with a high enough recruitment success to at least keep a stable population), randomly determining ...
Coel's user avatar
  • 837
10 votes
3 answers
561 views

What would be the structural impact of an oscillating orbit on a planet?

Notice : If you wish to know how to make an oscillating orbit with real-world physics, you can looky-look at this question which is following mine. My question focuses on the consequences of such ...
Tortliena - inactive's user avatar
9 votes
4 answers
2k views

Moons that can't see each other

Could 2 moons that orbit same terrestrial planet never see each other if they orbit the planet at same time? Moons have different mass and gravity.
AIwithstick's user avatar
9 votes
8 answers
3k views

Stopping Milkdromeda, for Aesthetic Reasons

Basically, there is a human civilization controlling the milky-way and an alien civilization controlling Andromeda. They are communicating and have decided, for some reason, that, though the ...
skout's user avatar
  • 2,068
9 votes
6 answers
791 views

Could a mass made up of certain elements or compounds "disrupt" a star?

Inspired by this interesting question-- let's say that the universe was just really, really out to get a particular star, such as our sun. Is there a perfect cocktail where a mass significantly ...
NegativeFriction's user avatar
9 votes
3 answers
379 views

How Can I Explain a Giant Equatorial Gash?

I have a moon in my story that has a thin, deep gash or canyon that lies on its equator and spans the entire moon. My original idea involved the sudden orbital decay of a ring system, caused by a ...
overlord's user avatar
  • 6,272
9 votes
1 answer
1k views

If we were to assume the shape of planet Popstar from Kirby is kept that way artificially, how would the shape affect its day/night cycle?

Making a semi-realistic Kirby Alternate Universe (AU) here. Popstar's shape is a result of a member of this powerful race using secret magics to alter reality in this AU. What would its day/night ...
Chickenpeep's user avatar
  • 2,503
9 votes
4 answers
577 views

How far should second star be in my binary system?

For a certain reason, I needed two habitable similar earth-like planets very close to each other. After various information gathering, I gave up on double planet and gas giant moons, because tidal ...
Failus Maximus's user avatar
9 votes
3 answers
595 views

How could formamide lakes form on an exoplanet?

I've been recently looking into alternative biochemistries for life and the environments were these could be found. I already asked a question about how ammonia oceans might form a while back. Today I'...
TheDyingOfLight's user avatar
9 votes
1 answer
403 views

Orange Suns and Blue Jupiters

I am developing a fictional planetary system in which a large gas giant planet (slightly less than the mass of Saturn), has migrated into the habitable zone during the formational years of the system, ...
Arkenstein XII's user avatar
9 votes
1 answer
484 views

Determining Planet rotation period that would allow for global Wind Cell

I'm trying to figure out how quickly a planet could rotate while also having a single air flow cell, such as Hadley cells, that would circle from hot pole to cold pole, etc. as in the case of Tidally ...
QuiGonJon's user avatar
8 votes
5 answers
3k views

Practicality of building a space station in the tail of a comet

In my novel, I want to feature a large (>5km) centrifuge space station that was built on/into a comet, and is in the comet’s tail whenever it passes close to the sun. It is home to many criminal ...
Whey_Isolate's user avatar
  • 1,347
8 votes
6 answers
5k views

If Earth had a smaller radius, but was rotating at the same speed, would its day be shorter?

I want to make a hypothetical planet that is 26% the mass of earth, with 64% the radius. Because I want a relatively short day to keep temperatures more stable, but I don't want a super fast rotation ...
Elhammo's user avatar
  • 975
8 votes
2 answers
3k views

What is the minimum size for the Sun?

How small could our Sun be and still "burn" with nuclear fusion and emit the same spectrum of light and other radiation as the real Sun does? Edit: The goal is to have a small sun inside a huge ...
user avatar
8 votes
4 answers
1k views

Would two people standing on opposite sides of a flat world be able to see the same constellations?

Quick drawing illustrating what I mean: Two people (humanoids, between 1 and 2 metres tall) are standing on the ends (less than 1km from the edge) of opposite faces of a flat world (approximately ...
Whitehot's user avatar
  • 2,569
8 votes
3 answers
2k views

If someone blew up mars, how screwed is earth?

Mars has a gravitational binding energy of ~5x10^30 jouleS. If a bomb went off on mars that released that much energy, how much danger would the earth be in. Additionally, would debris striking earth ...
Adam Kabbeke's user avatar
  • 1,973
8 votes
5 answers
498 views

Can early astronomers determine the gravity of their planet's "moon" without ever going there?

As I was thinking about space flight for my world, I thought about how they would need to know a planet's gravitational force before they could land, and found that humans figured out the moon's ...
Foosic17's user avatar
  • 1,266
8 votes
4 answers
826 views

Can planets collide and not melt together?

Ok so I've been going around on the internet trying to figure out whether or not when 2 earth like planets of similar densities and makeup collide is it possible for them to bounce off of each other ...
SlothsAndMe's user avatar
8 votes
5 answers
531 views

Galactic 'geographic' features, how could they impact galactic colonization efforts?

I have been wondering how galactic features could impact interstellar civilizations in the process of colonizing a galaxy (either andromeda or the milky way). According to this video these features, ...
JuimyTheHyena's user avatar
8 votes
2 answers
385 views

Time scale and mechanism to “realistically” remove Sol from the Milky Way

What is the fastest rate a star could be flung out of our galaxy and by what mechanism(s)? (i.e. from a gravity kick by a hypothetical passing hypervelocity black hole) Secondary question: how far ...
CmdrSpiff's user avatar
8 votes
4 answers
2k views

Pink Atmosphere [duplicate]

I recently came across a planet that I found pretty interesting but I can't seem to find much information about its characteristics. Its atmosphere is pink in appearance. After looking at the picture ...
Wither Fang136's user avatar

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