A rocky planet, similar to Earth in mass and composition, is set to pass through the solar system in one year's time. It has frozen oceans of water ice and a thin atmosphere of unknown composition. It's traveling at 50 kilometers per second, almost tangent to Earth's path around the sun. At its closest point it will be ten million kilometers away.

Physicists calculate that it will destabilise Earth's orbit and send Earth heading straight into the sun. The calculations aren't yet precise enough to find out what will happen to the planet.

Given current technology, and the fact that we have a year to plan, do we have a chance of surviving by starting a colony on the planet?

  • 4
    $\begingroup$ Do you need the colony to survive for a few years, or indefinitely? $\endgroup$
    – abcde
    Commented Oct 27, 2015 at 21:44
  • 10
    $\begingroup$ I've seen this film before....When Worlds Collide (1952) $\endgroup$
    – Thucydides
    Commented Oct 27, 2015 at 22:16
  • 5
    $\begingroup$ There's no chance unless it can be shown that Earth and the rogue planet will do a gravitational swap, Earth being ejected and the rogue being captured by the sun's gravitation, taking up an orbit approximating Earth's. The odds of this are infinitesimally small. Otherwise, the rogue would be uninhabitable. $\endgroup$
    – Monty Wild
    Commented Oct 27, 2015 at 23:53
  • 3
    $\begingroup$ Looking at the answers…seems like our best bet is to just blow the rogue up. $\endgroup$ Commented Oct 28, 2015 at 8:50
  • 12
    $\begingroup$ @BlacklightShining Believe me. We have had ample discussions on how to blow up, transform and otherwise obliterate planet-sized objects. The specifics of course vary, but the general consensus is that we can't realistically muster the energy to do so, even with far-future technology, let alone with present-day technology. $\endgroup$
    – user
    Commented Oct 28, 2015 at 10:18

8 Answers 8


I wouldn't think Earth has much chance of starting much of a colony there with current technology, though I think we could make a ship that could get there. (So depends on what kind of colony counts - in The Martian, growing potatoes technically counts, so yes we could probably do that. But we could do that in space, too.) We might be able to get some people there, but long-term survival would be difficult.

Seems to me the question becomes whether it's liable to be any easier than staying alive someplace else, like Mars.

The main factor in answering that, would be what the future trajectory of this planet is. I'd start by trying to actually find what possible trajectories meet your criteria. Earth speed relative to the sun is about 30 km per second, so if this new planet continued at 50 km per second, and was not headed for the sun, but part of the orbit included the Earth's position, then it's orbit will be at a more oblique angle than earth is. Given that it's going to change Earth's orbit enough to have Earth crash into the sun, that means this planet's orbit is also going to change. To be realistic, I'd want to have an actual set of motions where the numbers make sense. Knowing the future orbit would give very important information about the future conditions of that planet, mainly for temperature. Its rotation would also be important.

I'd spend some time running orbital simulations to find out if there is anything set of movements I can find that would be anything like this. Eg it's a great excuse to go play with Universe Sandbox or such.

Universe Sandbox screenshot

My first thought though is that I'm not coming up with any way that a planet could appear in a near-Earth orbit like that at such low relative speed, unless some sort of teleportation is involved. It also occurs to me that it's even harder for me to imagine any situation where we would not know the planet was coming for many years, not just one, again unless some sort of magic/unexplainable appearance from nowhere is involved.

  • 33
    $\begingroup$ +1 Just because I didn't know that Universe Sandbox existed, and now I do and I'm happy. $\endgroup$
    – Plutoro
    Commented Oct 28, 2015 at 1:02
  • 4
    $\begingroup$ What @AlexS said. Wow. $\endgroup$ Commented Oct 28, 2015 at 16:13
  • 3
    $\begingroup$ Thought: the planet falls in to Jupiter. It then slingshots into a slower orbit, and possibly around some other planets. Then, it swings really close to Earth (closer than the moon), deflecting Earth's orbit ... maybe to touch Venus? Earth either runs into Venus/Mercury, or its interaction with Venus/Mars/Mercury pumps it up until it can reach Jupiter, around which it hooks into the sun? It would be a billiards shot for the ages. $\endgroup$
    – Yakk
    Commented Oct 28, 2015 at 17:57
  • 4
    $\begingroup$ @Alex S, now I do and I'm $30 poorer. $\endgroup$
    – Octopus
    Commented Oct 28, 2015 at 19:37
  • $\begingroup$ @Yakk Yeah, I think you're right that it no doubt comes in a LOT faster, and then gets slowed down - Jupiter's a good bet, but then it needs to fall down to Earth level and end up in something sort of like an Earth orbit, which yeah might need to interact with another planet (now 3)... which also probably means its somehow on the plane of the ecliptic... best way to find a possible trajectory's no doubt working backwards, but it's astronomically (sic) unlikely. Also Earth would have many years to see it coming. $\endgroup$
    – Dronz
    Commented Oct 28, 2015 at 23:12

Once the rogue planet is out of the solar system it won't get any sunlight making it incredibly difficult to live on.

Maybe you can set up some sort of habitat and rely on nuclear energy (give that the rogue planet has ample deposits of uranium), but with current technology that would be virtually impossible.

We have limited number of rockets available, we don't have any landers to take us to the surface, much less any ready habitats we can deploy. A viable colony will need at least a couple of hundred people to get enough genetic diversity. Finding that many qualified people, screening them, training them, making sure they form a cohesive unit takes time.

Now imagine all the equipment you'll need. You have to assume the worst possible conditions - temperatures near absolute zero, unbreathable atmosphere, the surface covered by miles ice...

The space station and the Amundsen–Scott South Pole Station are the two places that are most similar to the outpost you are suggesting, but those need to be resupplied every few months, they are nowhere near self reliant.

  • 3
    $\begingroup$ It's even more similar once you cut the solar panels off the ISS and make the polar night last for hundreds of millions of years at the South Pole Station. $\endgroup$ Commented Oct 28, 2015 at 14:23
  • $\begingroup$ ... and no resupply ships to either. $\endgroup$
    – ventsyv
    Commented Oct 28, 2015 at 20:01
  • 2
    $\begingroup$ Even if you could set up a habitat that used nuclear, why would you? You are far better off building a space colony than you would be building a rogue planet colony. At least then solar panels are a viable energy source. $\endgroup$
    – Shane
    Commented Oct 28, 2015 at 21:59
  • $\begingroup$ @Shane Well, there are resources on planets, so that's a plus. But even then, it would be a better bet to stay in the solar system, and use, say, Mars. Or the asteroids. Either is probably going to be much more habitable than a rogue planet - unless there's something of interest on said planet... say, ruins of an alien civilization :P $\endgroup$
    – Luaan
    Commented Oct 29, 2015 at 8:54

No. We'd all die.

One year is, at the very best, enough time to design and build a lander that could bring fewer than ten humans from Earth to land on a rocky planet with Earth like gravity and a thin atmosphere. With the relatively high gravity and little assistance from an atmosphere to make a landing, the ship needs to carry a lot of fuel to slow the descent. Getting a handful of people there is a monumental task, let alone getting thousands of people and the equipment to survive on a frozen world.

Hopefully they'd realize that any close approach that could eject the Earth into the Sun would 1) take a long time for the Earth to get there and be destroyed and 2) cause significant havoc on the object upsetting Earth's orbit, likely destroying any fledgling colony there.

The fact that the "calculations aren't yet precise enough to find out what will happen to the planet" is not a promising point in trying to move humanity there.

  • $\begingroup$ +1 for noting the lander issue. I am more optimistic than most for building spaceships (we could finally use nuclear propulsion without having to worry about pollution) and survival on the planet (keeping warm is not that hard), but I am stumped about how to build landers for high gravity and thin atmosphere. $\endgroup$ Commented Oct 28, 2015 at 11:23
  • 1
    $\begingroup$ +1, I agree, but I think this would be a much more interesting question if we were given 15 years. $\endgroup$
    – Aurast
    Commented Oct 28, 2015 at 17:52
  • $\begingroup$ Matching the speed would be pretty much impossible using modern technology as well, let alone dealing with a safe landing. Even using the original 50 km/s figure for the rogue (which would likely leave it in the solar system for quite a while), this means having a spaceship that can do a 20 km/s delta-V orbital transit - that's more than Saturn V could do, if it started from orbit with no payload! And you don't have the time for anything fancy, like ion propulsion - you need lots of thrust. $\endgroup$
    – Luaan
    Commented Oct 29, 2015 at 8:59

"Physicists calculate that it will destabilise Earth's orbit and send Earth heading straight into the sun. The calculations aren't yet precise enough to find out what will happen to the planet."


1)It only approaches within 10 million kilometers, about 30 times farther than the moon. There is no way that will destabilize the earth's orbit, since the worst-case gravitational pull on the earth will be about 1/9 that of the moon, and that will occur for a fairly short time due to the high velocity.

2) If the effect on the earth is known, the effect on the rogue is known. You can't have it both ways.

  • $\begingroup$ I think you are forgetting that the Moon is only 1% of Earth's mass, therefore the rogue planet can be 100 times as massive, thus the gravitational force will be 1/9 on the Moons. Even that might be enough to change Earths orbit, even though I don't think it will make it "head straight into the sun" $\endgroup$
    – ventsyv
    Commented Oct 28, 2015 at 3:42
  • $\begingroup$ You are correct about the relative pull - my bad. I've edited. However, not only is the rogue's pull an order of magnitude less than the moon's, due to the high speed of the rogue the deviation will be small. $\endgroup$ Commented Oct 28, 2015 at 4:02
  • 1
    $\begingroup$ The immediate effect may be known, but maybe it's not known whether it ultimately enters a stable orbit (maybe the interaction with Earth sends it on to a complex series of interactions with the gas giants) - is that plausible? $\endgroup$
    – Random832
    Commented Oct 28, 2015 at 21:35
  • $\begingroup$ @Random832 - Generally, capture of a rogue (especially in a roughly circular orbit) is extremely unlikely without a massive collision. The problem is that once it has all that speed, there's no easy way to get rid of it. And keep in mind that a closed orbit (circular or elliptical) basically repeats itself. So if the rogue loses energy in a close pass by Jupiter, for instance, the resulting orbit will extend to the distance to Jupiter, and it will get very cold every orbit. $\endgroup$ Commented Oct 28, 2015 at 21:50
  • $\begingroup$ True, but its speed is actually quite low - we don't know the angle of approach, but even for a circular orbit, 50 km/s would be fine (though rather hot - Mercury's orbital velocity is ~56 km/s). In reality, the orbit would most likely be quite elliptical. We can't really guess at the angle of approach, because 50 km/s at Earth's distance from the Sun is just way too low for a rogue planet - once you include "somebody put it there at that speed", there's not much you can estimate. And if it had a collision before reaching Earth, it would likely be partially molten - not very habitable. $\endgroup$
    – Luaan
    Commented Oct 29, 2015 at 9:07

no. The rogue planet will exit the solar system an freeze. And I don't mean freeze like how Antarctica is frozen, I mean that it will approach absolute zero.

With current technology, we would not be able to create enough energy to keep the colony warm, never mind fed, watered and oxygenated.

If we had cold fusion reactors and also 100 years to plan the mission, then maybe.

Edit: I didn't think of geothermal warmth. So you want to build a thermal heat powerplant and giant hydroponics farm 1km under the surface? We could not even build that kind of colony on earth, given a 1 year time frame. Imagine then if every piece or necessary equipment then needs to be launched into space and landed of the other planet. We could not even provide the fuel to put it all up there.

  • $\begingroup$ The other answers have good points in them but I feel this is the key issue at hand. Even if the planet had natural resources for power that could heat/feed the population, the amount of infrastructure required to mine, refine and "burn" those resources is far beyond what we could feasibly transport to the planet in one go. $\endgroup$
    – thanby
    Commented Oct 28, 2015 at 6:25
  • 1
    $\begingroup$ The planet doesn't necessarily have to freeze solid...if the planet has a molten core you could always use geothermal. $\endgroup$
    – James
    Commented Oct 28, 2015 at 15:57
  • 2
    $\begingroup$ If the planet is travelling at 50 km/s while tangential to Earth, then it is not in a hyperbolic orbit and will not be leaving the solar system. Just because it entered as a rogue planet does not mean it can't be captured by the Sun. $\endgroup$
    – Samuel
    Commented Oct 28, 2015 at 17:03
  • $\begingroup$ @Samuel - At earth orbit, solar escape velocity is 42.1 km/sec. The rogue will exit the solar system. $\endgroup$ Commented Oct 28, 2015 at 20:33
  • $\begingroup$ @WhatRoughBeast You're right, I miscalculated. I suppose the rogue planet's velocity could change during its interaction with Earth, but it's not clear. So it may, in fact, escape. $\endgroup$
    – Samuel
    Commented Oct 28, 2015 at 20:43

A rogue planet will not get energy from Sun, so the colony would need to use nuclear energy to produce warmth and light as required.

Ordinary reactors use uranium that may not be easily available with reduced scale technology, but termonuclear reactors may need just water, or maybe tritium that could be purified from large amounts of water (assuming the planet has a frozen ocean with plenty of water available). Such devices are not used in production yet but they are under development.

If we get a small self-sustained colony, it may have much more time later to perfect the technologies.


Any colony based on current technology would only be habitable foe the period of time that the rogue remained in the habitable zone of our star. Once the rogue left that zone, the planet would likely rapidly become either too hot or too cold to remain habitable. This is assuming that the planet even had an atmosphere, and what you would consider "colonized" to mean.


Like other answers so far, I don't think that we have any chance of establishing a colony on that planet. I would like to add another reason, however, for why this is not possible with current technology.

You state that the planet is a year away and moving at 50 km/s at a right angle to the solar system ecliptic, heading for us. This puts its current distance at about 10.5 AU from the ecliptic and presumably a very similar distance from the Earth.

Uranus' orbit around the sun has a semi-major axis (distance along the greatest diameter) of about 20.1 AU. Since Earth's distance from the sun is about 1 AU, this means that the rogue planet is currently about as far away from Earth as is Uranus at closest approach. (This isn't very far at all in astronomical terms, but it is still quite a distance.)

We don't have the ability to go to Uranus in any way that would allow us to establish a colony around those parts of the solar system. Heck, we can't even do it to Mars, which is practically next door in comparison.

But wait -- it gets worse! This rogue planet is moving toward our solar system at those same 50 km/s, to within rounding error. Excluding solar probes like the HELIOS probes, the fastest spacecraft that have been launched from Earth move at about 15-20 km/s relative to the sun. Let's be generous and call it an even 20 km/s. Let's also be very generous and say we could get to this velocity without spending a lot of time doing fancy gravity slingshots, which almost certainly would be required in practice. Let's also say that we put all that effort into getting a spacecraft moving toward the rogue planet. Forget about the specifics of the spacecraft, let's just get it on the quickest possible intersecting trajectory at 20 km/s relative to the sun.

The relative speed of the two are now on the order of 70 km/s. The rogue planet is approaching the ecliptic at 50 km/s, and our spacecraft is moving away from the ecliptic (and toward the rogue planet) at an additional 20 km/s relative to the ecliptic.

In order to survive landing, we need to bring the relative speed down to effectively zero. In other words, for landing, we need to somehow come up with a delta-v (velocity change) budget of 70 km/s.

The way rockets work is by bringing mass (fuel), which is pushed in one direction to cause a resultant velocity change in the other direction. (Newton's third law of motion.) This lowers the mass of the rocket, which means we need less mass the next instant for the same velocity change. Conversely, going backwards, we need to bring enough mass with us to apply the change in velocity not just to the rocket itself and its payload, but also to the remaining mass of the fuel. This is known as the tyranny of the rocket equation.

When Apollo went to the Moon, after the TLI burn (translunar injection, which raised the spacecraft's orbit such that it went from a low-Earth orbit into an orbit that intersected the Moon, whether or not in a free return manner depending on the specific mission), the spacecraft was moving at about 11 km/s relative to the Earth. For any significant payloads, this is about the best we have been able to do so far. Besides the fact that this would be needed on the outbound leg of the trip, this left the Apollo CSM with very little additional delta-v budget; the LM had a bit to spare, for a soft landing on the Moon, but we are talking nowhere near the amounts that would be needed.

Even given maximum generosity and taking the velocity change from takeoff from ground to after TLI, your delta-v budget is now short only a measly 59 km/s. (In reality, it would be short a lot more.) Since lithobraking from even the slow and gentle 59 km/s to 0 km/s relative to the ground tends to be a bad idea, and because of the rocket equation's exponential nature, this is very bad news.

TL;DR: Even if we could figure out a way to establish a colony that would be able to survive, given current technology, we have no realistic way of getting there in the first place.

TL;DR;DR: In your scenario, humanity is doomed.

  • $\begingroup$ -1 if I could. The question says it's coming in at a tangent, not that it's perpendicular to the ecliptic. $\endgroup$
    – DCShannon
    Commented Oct 28, 2015 at 18:32
  • 1
    $\begingroup$ @DCShannon Fair point, but in what way do you feel that changes the conclusions of my answer? $\endgroup$
    – user
    Commented Oct 28, 2015 at 18:39
  • $\begingroup$ @DCShannon Additionally, it would still be tangent to the Earth's orbit, right? $\endgroup$
    – HDE 226868
    Commented Oct 28, 2015 at 20:24
  • $\begingroup$ @HDE226868 In all fairness, the OP doesn't state much relevant about the rogue's current orbit toward our solar system. We do know though 50 km/s (but not the reference frame this is in, which adds a pretty massive unknown) and one year away, which we can use to calculate an approximate distance (which came out to a bit over 10 AU, +/- realistically 30-50% I suppose depending on the velocity reference frame). I went in my answer with the velocity being in the sun's reference frame because that would avoid Earth orbital motion and allow for much of the effect the OP seems to be after. $\endgroup$
    – user
    Commented Oct 28, 2015 at 20:33
  • $\begingroup$ I don't know how fast the earth is moving through it's orbit off the top of my head, but your answer seems like its mostly based on how fast the planet is moving relative to Earth. If it's coming in at an angle tangent to Earth's orbit, within the ecliptic, and in the same direction as Earth, that seems like it would change things quite a bit. $\endgroup$
    – DCShannon
    Commented Oct 28, 2015 at 20:48

You must log in to answer this question.

Not the answer you're looking for? Browse other questions tagged .