Questions tagged [astronomy]

For questions related to planets, moons, stars and other celestial objects, and their motion on the sky.

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125 votes
21 answers
24k views

What would make scientists realize they were on a flat world?

Scenario: While poking around in an alien ruin, scientists discover a gateway which offers instant transportation to an Earth-like world. The Observed World: The gateway leads to an area that is ...
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81 votes
21 answers
8k views

Is it physically possible for a planet to have seasons of different lengths?

Those of you who have read Game Of Thrones will know that in the GOT world seasons do not have a fixed duration, e.g., a winter might last three times longer than the previous one. I find most ...
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81 votes
16 answers
12k views

Can stars that are not powered by nuclear fusion exist?

Stars generate their energy by fusing lighter elements into heavier elements. The most common reaction in Sun-like stars is the conversion of hydrogen to helium via the proton-proton chain, but ...
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68 votes
19 answers
16k views

How would an astronaut conclude he's on Earth, but 600 million years in the future?

Say we have a group of space travelers who have been frozen inside a sleeper ship for an enormous amount of time that left when Earth was recognizable. When they thaw out and reach their destination, ...
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66 votes
12 answers
16k views

Could a disaster kill all (human) life on Earth but leave astronauts in low orbit alive long enough to return?

There are plenty of threats out there that could terminate all life on our little planet in varying amounts of time (Solar flares, meteors and supernovas to name a few). Are there any disasters that ...
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64 votes
24 answers
13k views

How could a planet have a sky without stars at night?

Is it possible for a planet in our part of the galaxy to have a night without stars? I'm looking for some kind of natural phenomena that would hide the stars, but allow the sun to rise and fall as ...
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61 votes
10 answers
13k views

What would it feel like on the surface of a planet while it collides with another planet?

Let's say that something horrible has happened and a Mars-sized planet is knocked out of orbit and is hurtling towards an Earth-sized planet. How much time will they have? How will this affect the ...
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59 votes
20 answers
12k views

How would someone hide an asteroid in the void of space so only they could find it?

My story opens with an old man who arrives at his "personal" asteroid somewhere out in space. When he arrives, everything is powered down and he has to bring systems online before he can take his suit ...
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51 votes
2 answers
6k views

What would the sky look like from the surface of a planet with rings?

What would a planet's rings look like from the surface of that planet? Would the rings be perceived to be stationary or move across the sky, and would the alignment of the rings relative to the axis ...
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45 votes
11 answers
10k views

How long will it take to discover they live on a moon and not on a planet?

In my alternate reality, Earth is not a planet. It is a moon and orbits a gas giant (however it has all of Earth's characteristics, it is also full of humans and life as we know it). This is the only ...
42 votes
14 answers
8k views

Can I keep our universe, but without the speed limit (of light)?

It seems like nothing can move faster than light and this is quite bothersome for interstellar travel. It takes decades in the best case to get anywhere interesting in our little Milkyway (Many ...
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40 votes
5 answers
9k views

Can a planet survive a supernova?

The Sun has nowhere near enough mass to enter the branch of stellar evolution that would lead to a supernova, fortunately for us. However, there are planets that orbit stars that are destined to go ...
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40 votes
3 answers
10k views

Habitable moon of a gas giant: working out the sizes and distances

I am attempting to create fictional, stable P-Type binary system, featuring a gas giant in a stable orbit, with a habitable Earth-like moon. “Is a Jupiter-sized planet plausible in a habitable zone?” ...
36 votes
5 answers
6k views

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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35 votes
8 answers
4k views

Proving a world is in our galaxy

A portal about 30ft in diameter appears on the surface of our present-day Earth. It appears for about 5 minutes each day before disappearing. Hesitantly, scientists go through it and discover a new ...
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34 votes
7 answers
4k views

How to create an annual celestial event for a world

Yesterday while Green, Andy and I were recording new episodes for the podcast we stumbled upon a bit of a problem that we need someone with physics/astronomy knowledge to help out with. We want to ...
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34 votes
13 answers
4k views

Finding Earth on a star-map

One day, I am randomly teleported to somewhere else where I meet some aliens. These aliens are very technologically advanced and after figuring out communication, we establish a rapport. The aliens, ...
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33 votes
11 answers
6k views

What's an astronomical event which happened about 10,000 years ago, which humans could have noticed?

Bob is older than he looks. Specifically, even though Bob looks like he's in his twenties or thirties (it's hard to tell), he was actually born in Europe about ten thousand years ago, long before the ...
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33 votes
4 answers
967 views

What Factors Could Cause a World to See "Northern" Lights Much Closer to the Equator?

I'm currently designing a world where the inhabitants see the Aurora Borealis on an almost nightly basis almost all the way to the equator. The lights are so strong they rarely see the stars beyond. ...
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31 votes
14 answers
8k views

In a world without stars, how would travelers navigate at night?

On Earth, sailors would navigate the oceans at night by using the stars as guides; since there are no landmarks in the ocean like there are on land (save for the occasional island), that's pretty much ...
31 votes
5 answers
11k views

If Sweden was to magically float away, at what altitude would it be visible from the southern hemisphere?

If a chunk of land mass the size and position of Sweden took off and floated away in a straight line, exiting the atmosphere and orbiting earth, at what distance would it be visible from, let's say, ...
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31 votes
4 answers
3k views

What software can prototype a planetary system?

Is there any software tool for quickly prototyping a planetary system? Ideally this should: Allow for placement of planets of different sizes and masses around a star. Allow for examination of the ...
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31 votes
2 answers
2k views

Would life on the edge of the Sagittarius Dwarf Spheroidal Galaxy see the whole Milky Way in the night sky?

Here's an intriguing thought - I think so anyway. Let's suppose for a minute that there's an Earth-like planet with sentient life orbiting a star near the edge of the Sagittarius Dwarf Spheroidal ...
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31 votes
5 answers
7k views

Creating a realistic world(s) map - Stars

This Query is part of the Worldbuilding Resources Article. This question is a sort of follow-up to Samuel's previous world map question, Creating a realistic world(s) map - planetary systems. Lots ...
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30 votes
14 answers
7k views

Would 'cheap' FTL make powerful telescopes obsolete?

Imagine we have a faster-than-light drive which costs ~$250,000 USD per drive and can propel an ISS-sized craft at 1000 times the speed of light. It is reliable and has safeguards that stop it from ...
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29 votes
17 answers
7k views

How could a planet have one hemisphere way warmer than the other without the planet being tidally locked?

I would like a planet that's a tropical paradise on one side but covered in ice and glaciers on the opposite side, whether it be the Southern-Northern or the Western-Eastern hemisphere. I know it ...
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29 votes
8 answers
4k views

Building the Death Star with today's tech

I found an interesting Wikipedia article, quoted in an answer here. I'm looking into writing a story where someone has built a Death Star. The purpose of this craft is important to the story (and the ...
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28 votes
13 answers
6k views

What could make a planet more radioactive at night?

In the story of my video game, I want a group of colonists to land at dawn on an alien planet and have to terraform or build protective structures before sundown (several earth days). I want the ...
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28 votes
6 answers
7k views

Why didn't we detect that exoplanet before?

In my world an alien creature claims to be from an earth-like planet orbiting a 500 light-years away solar analog star. It tells us that the planet has x mass, y diameter, z orbital period, that ...
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28 votes
6 answers
5k views

Exactly how far apart are nearby stars from one another? [duplicate]

I am working on a hard(ish) science fiction space opera story, and I would like to get a good handle on distances between stars so that I can calculate appropriate travel times. There are a lot of ...
28 votes
17 answers
8k views

Is there any conceivable way to "turn off" a star?

In my world, a group of "lamplighters" seek to turn off unused stars to conserve the energy for later use. This serves a few purposes, but mainly: It delays the heat-death of the Universe to some ...
28 votes
5 answers
11k views

What would the effect be on Earth if Mars disappeared?

What would the effect on Earth be if Mars, in the space of one second, disappeared from the Solar System? Just simply was gone, leaving no residue, and leaving the space where it had been like it had ...
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28 votes
5 answers
5k views

Can a dedicated amateur astronomer spot a rogue asteroid?

Meet Joe. Joe is generally an average person with one special trait: He loves astronomy and star gazing. However, Joe has a great paying job as a web developer. He earns 120 000 USD yearly and has a ...
28 votes
6 answers
6k views

How deep can the ocean plausibly be?

I want to have planet with as deep an ocean as plausibly possible. How deep can I go given these restrictions? Planet must be in habitable zone of a star Generally, planet should support life Size of ...
27 votes
7 answers
7k views

Could life form in outer space?

All life we know of to date (presumably) formed on a rocky planet (more precisely: earth). Fiction has been written about life in more exotic locations. Though as far as I know, these lifeforms were ...
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26 votes
13 answers
6k views

How can a planet have a deadly eclipse-like "spotlight"?

A solar eclipse occurs when the moon passes between the Earth and the sun. The result is a giant shadow that sweeps across the Earth's surface. This world has the opposite phenomenon. Instead of a ...
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26 votes
20 answers
6k views

Making a Planet Seem Uninhabitable

How can I make it so that an otherwise colonizable planet (or moon) can (entirely naturally) seem uninhabitable from a certain point on its surface? Background: There are a series of immovable gates ...
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26 votes
7 answers
3k views

On a planet without seasons, how would people track years?

On a planet without axial tilt and with a roughly circular orbit, there would be no seasons. The climate on the planet would be, as far as I can tell, exactly the same at any time of year, and the ...
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25 votes
7 answers
7k views

How would skeptics know that a single-engine plane could not destroy a falling meteor?

So I'm writing a story and decided to use Hida Furukawa as the location. It has a high school with a field of 650 ft that theoretically could be used for a small aircraft to be use to take off. In the ...
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24 votes
8 answers
4k views

Can the Little Prince's planet actually exist in our universe?

This is a drawing by my daughter which inspired one of the elements in my story/world: The perspective is a little bit mixed here (certainly I don't have a 15 meter-high volcano in this world), but ...
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24 votes
5 answers
4k views

What do Martians use for months and weeks?

Assume Mars has developed an indigenous civilization of its own, perhaps as seen in Edgar Rice Burroughs' A Princess of Mars. Much like Earth, Mars' years and days would be significant for any ...
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23 votes
11 answers
3k views

Is it possible to have a sun with visible phases or cycles?

Is there a scientifically plausible way for a habitable world to have a sun that undergoes a regular, dramatic, and easily observable change? One comparable in visual impact to an event like a solar ...
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23 votes
6 answers
2k views

Scientific explanation for a exceptionally bright night sky

On an alternative Earth live the people of Tcelonia. One of their founding myths goes that, in the dawn of times, when they were under the menace of being attacked by an enemy population, for an ...
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23 votes
11 answers
4k views

Can you replace a sun with a burning moon?

In our solar system light and heat are, of course, provided by the sun. I was wondering if a comparable effect might be had by positing a burning moon instead? So rather than a true star, you'd have a ...
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23 votes
5 answers
2k views

Is it safe to orbit HDE 226868?

I'm considering a story where an exploration is devised to explore a binary system containing a black hole; the choice is Cygnus X-1, with its companion supergiant star HDE 226868. It would likely be ...
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23 votes
4 answers
2k views

How would solar activity change if the Sun was impacted by a planet?

Suppose that a planet whose size was somewhere between the sizes of Mercury and Jupiter impacted the Sun. Would such an event change local stellar activity sufficiently enough and for long enough ...
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23 votes
3 answers
3k views

How big a black hole is needed for this story?

The story begins in classic disaster film style. A small rogue black hole is approaching our Solar System. It isn’t going to get close enough to destroy everything, but it will agitate our Sun, ...
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22 votes
12 answers
9k views

Is a "long exposure"-like night sky possible?

Under what conditions would a planet's night sky look like this to the human eye? The angular speed of the stars relative to the planet would need to be high enough for the stars to blur into ...
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22 votes
10 answers
6k views

How could the current model of the Solar System have been recognized and accepted earlier?

Many factors in history have contributed to society's taking a long time to accept the heliocentric (= the Earth orbits the Sun) model: the first that come to mind immediately are religion and, more ...
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22 votes
6 answers
2k views

Close the door on your way out - Life lit by a blue dwarf star

I'm seeking a hard science setting for a piece of xenofiction with a decidedly non-sciencey feel. That said, there is no magic or magic technology. The idea is as follows: A red dwarf star has a ...
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