A major plot point for my story is the Protagonist stumbling upon a planet that was purposely hidden from the rest of the galaxy (at the edge of the galaxy) as it's being used by high level government officials to conduct a secret trade of a commodity that only this planet has and that uses the planet's population to harvest.

It was recently pointed out to me that my original idea (IE. a network of jammers) wouldn't meet the science of being able to hide a planet from star maps / ship scanners / etc. So the question is:

What are some plausible ways for an government agency to hide a planet from normal travelers / star maps / sensors / etc.?

Based on comments so far, I've been thinking...would there be a way to make the planet look like a black hole from any sensors/scans that would fool people from wanting to go to that area of space?

(Thanks in advance for your consideration of this question. I greatly appreciate the feedback provided already. Thanks)

  • $\begingroup$ Since this is galaxy spanning, I presume you have FTL? $\endgroup$
    – Schwern
    Mar 5, 2020 at 22:43
  • $\begingroup$ That's correct. $\endgroup$
    – Primordial
    Mar 6, 2020 at 0:34

11 Answers 11


It has a secret identity.

The universe is full of crappy planets that no-one would want to visit. Lava worlds. Stinking gas giants. Acid blasting Venuses. Atmosphereless Mercury hellscapes.

Your planet is just another one of these - not a place for life of any kind, or machines, or anything but a note in the charts. Or so the story goes. But if for some reason you orbit it, you may realize that what you see does not match what is listed for this planet in this system.

The residents of the planet maintain the secret identity by limiting or preventing radio transmissions, artificial lights, or anything else that might at a distance give away the fact that there is more to this planet than the star charts state.


You could move it away from any star, making it a rogue planet.

Basically, any planet near a star is detectable through a few different means like eclipsing, redshift of the star caused by the planet's mass, and simply viewing the planet using the star's light if close enough.

If your planet isn't near any star, then it will probably be completely undetectable except for when it eclipses a star from the observer's POV, and if it's at the edge of the galaxy that will rarely/never occur.

The downside of course is that your planet is perpetually in the dark and has a frozen surface.

  • $\begingroup$ This is the answer I was going to post. It still has to resolve the part of the question where it is mentioned that the planet has inhabitants. Life as we know it generally needs heat for a very long time and I'm not sure how easy it is to have a planet generate heat from its own core for billions of years. Hopefully someone can chime in on that... $\endgroup$
    – Muuski
    Mar 5, 2020 at 17:01
  • 1
    $\begingroup$ What if the rogue planet was actually the moon of a rogue planet? A massive gas giant goes rogue, taking it's Mars sized moon with it. The moon (where the inhabitants live) get's its energy from the tidal forces of gravity from the giant. $\endgroup$ Mar 5, 2020 at 17:41
  • $\begingroup$ @Muuski Chime. Actually, rogue planets, given a sufficiently dense and reflective atmosphere can retain heat surprisingly well to the point of liquid oceans. Of course, that kind of an atmosphere isn't breathable by humans, but... $\endgroup$
    – Halfthawed
    Mar 5, 2020 at 18:18
  • $\begingroup$ @Muuski Maybe a large rocky planet with a very thin crust? And lots of tectonic acitivity. $\endgroup$
    – DKNguyen
    Mar 5, 2020 at 23:01

It is an icy moon with a subsurface ocean

Our solar system has several moons orbiting gas giants which are though to have rather large subsurface oceans under a thick layer of ice. The Saturnian moons Dione, Titan and Enceladus are thought to have subsurface oceans, and the same is true for the three big Jovian moons Europa, Callisto and Ganymede. Even Pluto may have a subsurface ocean.

Such moons need not be near any star, as heat is generated through tidal forces with the host Gas giant. In the case of Pluto, the heat comes from interaction with its closely orbiting moon Charon. The planet/moon system could be too far out in a solar system to be thought worth examining closely (or it could be a rogue planet/moon), and superfical examination of the moon would not reveal any life benath the ice shell.

It is possible that intelligent life could develop on such a moon (I wrote an article about that three years ago). The extreme pressure at the bottom of the ocean may produce some rare crystal or whatever that can't be found elsewhere, or maybe the lifeforms create some very complex organic substance that can't be replicated (like the spice melange in Dune). Elevators could be drilled through the ice froma camouflaged surface station for trade. People going down would have to wear a very efficient high-pressure suit, or robots are handling the trade.


You do not really need to. All you really want is that nobody visits the system your planet is in.

The system is far away so going there requires lots of money and far enough from trade routes that even smugglers and pirates have no reason to go that far from authority.

The area of space is also distant from possible assistance and thus going anywhere near your system requires a permit from the government for the specific locations you plan to visit at specific times and activities you plan to perform. So that help can find you, if something goes wrong, of course.

Your government has reserved the area for its future expansion and other nearby governments have accepted that claim, at least provisionally, so that they do not visit the area without asking your permission and providing the necessary documentation of planned activity. They also accept your authority to enforce those rules.

You already provided the full survey data on the system for general access. It is fully accurate and gives no excuse to think something is wrong or interesting with the system and go see for yourself. Admittedly it does omit certain peculiar details about one of the planets but if the substance really is unique to the planet, nobody can deduce its existence from the public data on the system. No reason to fabricate lies that some routine check might discover and label as "invalid, send someone to get valid data".


You can't. Planet will have mass. Mass will create gravitational lens. From all angles. How this was told in some movie "there is nothing there but all the data point that there should be something".

So you don't hide it. Just don't. Put a big sign on it "We have poisonus snakes, spiders that eat snakes, sharks that eat spiders. Also there is no water. This planet is made out of hydrogen. But hey, if you're stupid enough you can come here. Please sign this weaver we have full rights to sell movies about how stupid you were to come here and die".

Make it Dallol fields of planets. And of course, control scientist that go there. Because it's very dangerous. Then murder them, send some fake results in line with your story and fake their death as planet visit related.


A major plot point for my story is the Protagonist stumbling upon a planet that was purposely hidden from the rest of the galaxy (at the edge of the galaxy)

This reminds me of the Isaac Asimov novel The Stars, Like Dust, where at one point a character points out that the odds of arriving near an inhabited star after doing a blind jump is astronomical - I don't recall the exact number offhand but it's something like 250,000,000,000,000 to 1. Of course, if you're blind jumping around stars, the odds are slightly better, but still very, very low - there's an estimate 250,000,000,000 stars in the Milky Way, after all. Now, since the rather astronomical numbers of space travel aren't really easy to wrap a head around, it's easy to handwave numbers, but it'd still be better if you didn't. Which means there should be a reason that the protagonist knows about the planet, but also a reason that no one wants to go there. Which means that the government isn't hiding this planet by denying all knowledge, but rather they're hiding this planet using some kind of a trick to make people not want to go there. And the answer should be simple enough - Area 51.

Area 51 is an American military installation which serves as an experimental test facility for the United States Air Force. It's also the location which serves as the basis for several conspiracy theories of government cover-ups and UFO landings. (There was also a minor event to storm Area 51 a while back). But everyone, of course, knows that even if there was secrets, they wouldn't be in Area 51, because only crackpots believe in Area 51. Which, ironically, makes Area 51 the best place to store UFO coverups, if they did exist.

So what if there was a galaxy-spanning Empire which needed to hide things on a planet, but it was impossible to conceal that they were doing things involving the planet. They could hide whatever it was they were doing, of course, but they couldn't hide that they were involved with the planet. It would seem that the optimal strategy would be disinformation - turn that planet into an 'Area 51' equivalent - the official story is that it's a test planet for the Imperial Navy. Sure, there are crackpots who believe that the Navy is up to something even more top secret there - but those are the crackpots and anyone smart enough to have a ship that can travel through hyperspace knows better than that, not to mention that the planet is sufficiently guarded (because it's a military facility). In short, you now have an excuse for a military presence to guard the base and a justification for any weird rumors - they'll just be written off as crackpots. And, all the while, of course, the Empire will be throwing out false information about a completely fictitious planet in a completely fictitious star system which is there actual base - no coordinates, of course, but supplies being marked 'to Destination X', fake invoices, the works.


Make your planet hard to spot, and uninteresting. Play the odds.

There's a lot of planets.

The Milky Way is estimated to have over 100 billion stars each with at least one planet. If you had 1000 ships each visiting a star per day it would take 275,000 years to visit them all.

Space is big. Planets are not.

Space is really, really, really, astonishingly, mind-bogglingly big. On that scale planets are not. 99.9% of the mass of a solar system is in its star, that 0.1% is left over for planets. Rocky, Earth-like planets are particularly small. We live a small crumb of the universe; a peculuarly wet and warm and stable crumb, but a crumb.

Planets are hard to see.

Planets emit no light of their own, only reflected starlight.

Currently we spot planets which are very large and/or very close to their star. Large, close planets make their star wobble just a little bit, and we can see that if the wobble is large enough. Or, if their orbit happens to be in line with the Earth, we can see them as they pass in front of the star if we happen to be looking just then.

Even if spotted, someone or something then has to pay particular attention to it out of the 100 billion planets.

Your "secret" planet.

Even with advanced technology, the fundamentals remain: out of the hundreds of billions of planets, someone has to spot and take an interest in your planet. Don't give them a reason.

Pick an area far away from civilization centers which would have good star-scanning capability. Perhaps on the opposite side of the galactic center. In that area choose a massive star with a large habitable zone and nothing of particular interest in the system. Pick an uninteresting rocky planet at the far edge of the zone. Such a small, far away planet will not cause its star to wobble, nor will it be likely to be caught in a transient. This minimizes the chances it will be spotted at all.

Control your emissions to avoid any tell-tale traces of human activity in the atmosphere which might suggest that it's occupied. Excessive amounts of methane, short-lived radioactive material, and so on.

That's about it. Depending on your technological level, it's not necessary to hide underground, or avoid having satellites in orbit, or otherwise mask your surface and orbital activities. They can't be detected from a distance, and there's no reason for anyone to visit for an up close look.

Have a cover story.

Just in case anyone does visit, have a cover story and a reason to keep yourself a secret. You're an independent, quasi-legal mining operation and you'll pay handsomely (but not too handsomely) if the interloper would kindly keep quiet about their operation.

After they leave and their ship is well away from your planet, maybe their ship has an "accident".

...would there be a way to make the planet look like a black hole from any sensors/scans that would fool people from wanting to go to that area of space?

Not without getting into absurd technology.

Unlike in the movies, black holes aren't particularly any more dangerous to get near than any other object of a similar mass. If a star turns into a black hole you don't suddenly get sucked in, it has the same gravity as before.

Presuming you can't change the mass/gravitational pull of the planet, it has to be a planetary mass black hole with the same gravity as a planet. Which is to say not much on an astronomical scale. It would pose no danger to anyone entering the system.

Then there's replicating the key aspects of a black hole: gravitational lensing and the event horizon. A black hole the mass of the Earth would have an event horizon of about 1 cm meaning any light within 1 cm cannot escape. Light which gets close will be bent. If you can replicate this, you effectively have planetary cloaking technology.

Very large black holes may have accretion discs. If large and violent enough this might be something space-farers want to stay away from, but again, this is a tiny black hole.


Dyson Sphere around the planet with a cloaking surface on the exterior (vanta-black and EM spectrum absorbing materials)


So ... hiding a planet. Let's break the strategy into three steps:

  1. Hide the Planet. Blame a random guy if it is ever found lost
  2. Make the area uninteresting. Do your best to make sure that nobody wants to go there
  3. Hide from the sensors. Make sure that a casual search by people that do find it does not give you away.

There is no Planet Spoon

You are a government agency. This means that you should be the official point of call for the star charts of your region of space. As such, your start charts do not mention the planet. The star is there, it is too large to deny its existence, but the planet that surrounds it is not.

Blame somebody for losing the planet should incontrovertible evidence of it existing is ever found.

If you cannot just redact the planet, then as a government agency you admit its existence but lie about its statistics. The key is to keep the numbers accurate to explain the physics there but make the changes a place that people do not want to go to. This leads to ...

Do Not Go Over There

This planet is at the edge of the galaxy. Odds are this is already a place that people do not want to flock to in drove unless there is a good reason for it. Your agency's job is to keep it that way.

Keep it off of the standard trade routes and do not invest much (or allow much investing) in the infrastructure over there. It's already likely far enough away that no company will find profit there unless FTL is stupid cheap, and all surveys say that there is nothing interesting over there -- see above.

In addition, play up the relative lawlessness of the galactic frontier. With nothing of interest there, that means little in security forces over there should something go wrong. Space Police will be in shorter supply over there since there is nothing to really watch over.

Lastly, don't let your runs to this planet be known. People going somewhere that uninteresting is interesting in itself. But you are a government agency, so you should be able to hide these trips within another group or bucket so far that it would take conspicuous digging to find them. Alternatively, a separate agency ostensibly set up for outer galaxy surveillance and protection has a hidden second job. Refueling at a planetless star would be better than sucking the fuel out of one with life, right?


Sensors are the problem. A strong enough sensor array will bust the case wide open faster than a cunning plan by the Scooby Doo Gang after Velma finds the last clue.

It can be assumed that with appropriate foresight and preparation, the groups that would bring the best sensors are deterred by the first and second points. In short, they should have no reason to go there in the first place. The good sensors need to be close by to find out out anything deep and probing. This means, that you really need to fool the casual scans of a planet and any scans that might indicate that people want to land for whatever reason.

Hiding your operations underground is a good first step. Casual scans will be thwarted by enough natural planet between them and you as well as by a lack of visual infrastructure on the surface. Not having anything orbiting the planet or system outside whatever standard things that identifies the owner of the system as your government is a good second step.

Should they land, then do not have the entire planet terraformed into something that clearly indicates things are here where they shouldn't be. Keep the planet looking as natural as possible and don't provide any reason for people to probe deeper than casually. If the planet has native residents, let them be. A lush planet missing half an ecosystem is a red flag to anybody that catches onto that detail.

This is obviously not a foolproof plan, but the stragglers that find something out can be ... dealt with. Those that find the place are put to work in resource acquisition. Also saves money on HR costs -- your workers are legally dead so who are they going to tell?


Hide in plain site [pun intended].

Where is the Second Foundation located?

The real problem with your premise is that of moving the goods. Just as with embezzlers on Earth today, it's relatively easy to disguise whatever is being done to collect the special sauce; it's much harder to ship it off-planet without a stack of incoming and outgoing cargo ships. That's what you need to figure out how to hid.

  • $\begingroup$ Elaborate and explain. I know what you’re referring to with the Second Foundation, and was about to post something similar when I saw that you had done it already, but does the person asking the question? $\endgroup$ Mar 7, 2020 at 10:44
  • $\begingroup$ @Fivesideddice One might hope that anyone trying to write SF is intimate with the Foundation Series. If the OP doesn't I'll just have to tell him to "Teleport offa my lawn" $\endgroup$ Mar 9, 2020 at 14:16

If you do not really care about the scientific accuracy of your story, there can be some generator that can transfer the planet into slipstream space, or the Star Wars equivalent of hyperspace. Perhaps your protagonist got there by some quirk in the space-time continuum. Let your imagination fly! If you are not bound by the shackles of reality, anything can be possible.


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