153

Kamacite and Taenite Kamacite and Taenite are both Iron-Nickel alloys found (on Earth) only in meteorites. Kamacite's composition is in the 90:10 to 95:5 Fe:Ni range. Taenite's composition is from 20% to 65% Nickel. Kamacite, in particular, can form massive crystals. A kamacite crystal listed in table 1 here had dimensions of 0.92x0.54x0.23 meters, and a ...


128

Dust cloud. The star may be residing in a dust cloud with no other stars nearby. This interstellar dust will create a faint nighttime glow, and can be thick enough that no other star's light can be visible on the planet.


98

Give it a circumstellar cloud of oxygen. Some planetary nebulae, such as NGC 6826, appear green because of ionized oxygen. Image in the public domain. Yes, this is a true-color image. I see no reason why you couldn't surround the star with an extremely dense cloud of hydrogen, containing a relatively high fraction of oxygen, which would absorb light and ...


74

Ganymede No matter which one you go for, blowing up a planet is going to make a lot of shrapnel. An asteroid of several miles long is an extinction-level event, and you've just thrown millions of such asteroids, along with billions of smaller meteors, all over the Solar System, and mass tends to fall towards gravity wells. Chances are, enough of those are ...


69

Perhaps their planet is on the inside of a giant Dyson sphere that was created by an ancient civilization. This would be a vast solid shell that surrounds their entire solar system, the inside of which is covered with solar panels in order to collect as near as possible to 100% of the energy output of their sun. Naturally, this would block their view of the ...


59

Since Santa's death fortress is based on the North Pole of Neptune, he shouldn't have too much trouble making it to Mars. He and all of his reindeer are robotic, so they won't have any trouble surviving in space. I imagine that Santa probably wouldn't want to show up the same night as he does on Earth, since it takes time to give presents to all the good ...


57

C. Must not create any phenomena that would have devastating consequences on life on the planets (i.e.: no radiation, excessive heat, energy surges) except for the diminishing of the Sun's current Solar contributions. The Sun just reduces in size, energy, and mass, but otherwise functions normally. That is not possible, for three reasons. About a third of ...


55

The Asteroid belt. It has similar requirements for life-support systems as the moon. With the additional need perhaps for some areas with simulated gravity. It is next closest in terms of energy required to get to and from the orbits. It is still close enough to the sun that collecting solar energy is workable (the farthest out we have used solar panels is ...


51

One possibility is for the surface of the planet to be covered in highly luminous matter. Perhaps all the surface is an interconnected network of bioluminescent life. There is no moon (assumed because you make no mention) and the high levels of light pollution at night will blot the stars out. You could combine with a naturally hazy atmosphere and cloud ...


49

I assumed, based on the limited knowledge I have on the subject, that all star systems have ellipsoidal orbits (the star being in one of the two focal points) just like our own You are right, this is one of Kepler's law, the first. Another one, the second, states that the line connecting the star and the planet swipes equal areas in equal times, or, to put ...


46

Switch planets. Venus has a permanent, thick, global layer of clouds that covers it. We cannot observe its surface from the Earth. Even satellites can only peek at its surface through radar. The only times we got a glimpse from her surface were when the russians sent some probes there, but no probe survived for more than a couple hours if my memory serves ...


44

I'll start with Earth Earth is hurling through space at a speed of approximately $29.78 km/s$ If the sun were to disappear, the Earth would move in a straight line until the sun reappears. Since there are $259,200 seconds$ in three days that gives Earth the time to travel $29.78 km/s \times 259,200 s = 7,718,976 km$ That's quite a distance. Since the ...


40

Organic Your mineral could have been deposited millions of years ago by a specific type of organism, class of organisms, or type of biome. For instance, you might have a forest that produces lots of some interesting organic compound, which when put under intense pressure and heat, forms some mineral with useful properties. Because the relative scarcity of "...


40

Don't make space iron better. Make all other iron worse. Read up on Low Background Steel. Have all of earth's iron contaminated with something, and less useful than we think of iron being. At some time in the past, there was a cataclysmic event which contaminated all iron with something. Maybe the Elder Gods awoke, and their presence cause decay or ...


39

Wormhole [A,C,D,E,F,G] A traversalable wormhole would be an excellent mechanism to remove mass from the sun. A wormhole is consistent with general relativity while avoiding all of the pitfalls of violently moving mass from the center of the solar system (which could cause all kinds of orbital perturbations that would be chaotic or even fatal). [B] Would ...


37

It is never night. https://www.tripsavvy.com/midnight-sun-in-scandinavia-1626397 Your people live on the north pole of a tidally locked planet. Like the countries near the north pole on our planet, in summer the sun never sets. It is always summer for your people. Why do they only live near the pole? Maybe it is hot farther south. Maybe there are ...


36

My choices: Ganymede and Callisto (and maybe Titan) This is perhaps a bit of a buzzkill, but I honestly would not recommend colonizing much in the solar system besides the Moon and Mars. Here's why I would take a lot of bodies off the table: Mercury - Too hot on its sunny side for colonization (up to 700K) and too cold on its dark side (down to 100K). ...


35

Get the ship as close to the sun as the ship can tolerate then maintain position between the sun and the earth. The sun is a strong gamma ray emitter. As long as the ship stays between the earth and the sun, any gamma rays emitted will just look like noise against the solar gamma radiation background. Any IR, visible, UV, or radio emissions will also get ...


34

Phil Plait of the Bad Astronomy fame: Why are there no green stars: "The fault lies not in the stars (well, not entirely), but within ourselves". Followup: Green objects in space: "So, maybe, maybe, there is one intrinsically green star, but even then it’s controversial". But is there a star that’s intrinsically green? Zubeneschamali is the second ...


34

Circular orbits are not practically possible From Astronomy.SE, there are a variety of reasons why orbits are not circular. There is relativity, there is planetary flexing with gravity, there is unequal radiation from the planet's surface (the sunny side reflects and radiates more energy into space, generating net thrust). Then there are the effects of any ...


31

The problem is that "focused" does not really mean "concentrated" Everyone that has ever played with a magnifying glass "know" that you can take the light from the Sun and turn it into an infinitely concentrated dot. This is in essence a variant what you are trying to do. The problem here is two things: The only reason you can get a dot that small is ...


31

Don't. Please just don't. I have no idea how short such a cycle can be, but I can tell straight away that the idea of people capable of interstellar travel and colonization of new worlds not noticing it in advance is not credible. I am pretty sure that every starship has navigation systems that can rapidly and accurately calculate all possibly relevant ...


29

The point directly opposite Earth on the other side of the sun is called the L3 Lagrange point. It's not quite at the same distance from the sun as the Earth is, assuming that the body residing there is smaller than the Earth, since both the gravity of the Earth and the sun pull on it. However, the L3 point is a saddle point in terms of gravitational ...


29

Skimming various gasses from the Jovian atmosphere or using superscience to extract metallic hydrogen from deep below the surface only taps a small amount of the potential resources available. Since you explicitly said "Jupiter" and not the Jovian system, I will set aside the 67 moons or thousands of asteroids on the L4 and L5 trojan points. Jupiter has a ...


28

Fun question! I would expect at the start that Christmas would be celebrated when it happens back on Earth. As a species we'd all celebrate it at the same time (relatively). Meaning that Martians would likely celebrate it twice a (Martian) year. However, what happens as the colony ages and becomes more Martian things will likely change. Some of the ...


28

How difficult would it be? Unfortunately, your timeline is too tight for any of the easy options to work. The mass in the asteroid belt is highly concentrated. Between them, Ceres (~30%), Vesta (~10%), Pallas (~8%), and Hygiea (~5%) make up about half the mass of the asteroid belt. Combining these into a single body is (relatively) easy, but slow and ...


27

One problem: I want the results of the terraforming to be something of a surprise to the arrivals. That requires that there be something that keeps Earth from getting broadcasts from the Martian robots and prevents Earth from observing Mars through telescopes, […] Not necessarily. The arriving colonists will not be politically powerful people with ...


27

The laziest answer is to just wait a while. If you wait an incomprehensibly-long while, eventually the expansion of the universe will move all currently near-by light generating bodies outside of our visual distance. In other words, civilizations in the far-future may never realize that anything other than their own sun exists, because nothing else is ...


26

TL;DR: Yes, helical motion around a ringworld is possible. However, it is far from uniform at larger distances (≥ 0.04 AU). Summary of results: For a toroidal ringworld with mass $M_R = 3 M_\text{star} = 3M_\odot$, central radius $ a = 1 \text{ AU}$ and inner radius $b = 10^{-4} a \simeq 15000\text{ km}$ (hence density $\rho \sim 8800\text{ kg/m}^3$, ...


25

You can have 36 habitable planets/moons as follows (all shamelessly taken from here): We can fit six stable orbits into the habitable zone. Each orbit has two sets of binary Earths. These are Earth-sized planets with Earth-sized moons. Each binary planet is in a Trojan (co-orbital) configuration with another binary planet, separated by 60 degrees on their ...


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