Aliens are building a "space highway" through our solar system. They love our Jupiter, so they decided to put gas pump with bar on its orbit.

After realizing that we cannot do anything about it and if asked, they can fake our agreement, they decided to put such gas pump there without even trying to contact us.

The question is: Who on Earth, and how fast, will realise that something alien is happening around Jupiter?

Background for space highway: It is set of precalculated dimensional jumps which will always throw you out near something with gravitational pull. Then you, as driver of vehicle, can decide if you are going to use gravity of such object for next jump or if you will make a stop here and refuel. (Or take kids for a snack to McJupiters)

Aliens use mixture of FTL communication and normal radio waves. Neither the ships nor gas station try to hide themselves, because they assume "everything is legal"

Such gas pump opened for business half an hour ago. Who can realise something is going on?

And especially, can average space fan with customer level equipment see something there? Assume size of such pump as big as Phobos

This is "local highway" - assume 10 000 vehicles going throught the jump during an Earth day. The gas pump can hold up to 15 space vehicles at a time. Common alien ship is about as big as ISS is. Pump itself has artificial gravity.

The pump has "standard" beam, which you approve in your ship computer and all navigation is done for you. Which means, that most sub-FTL communication is done directionally

  • $\begingroup$ How big a structure is this gas station+bar? How large are the ships that come through, how "noisy" are they in the EM spectrum (e.g. are they pumping out lots of radio waves or using high-powered radar?), how many are coming through, and how long do they typically remain in orbit? Those that visit the station, do they dock to exterior docking ports, or do they fly inside the station? $\endgroup$
    – Kromey
    Apr 24, 2015 at 18:19
  • $\begingroup$ Added info. As staded earlier, the pump is 25 km big structure. $\endgroup$ Apr 24, 2015 at 18:29
  • $\begingroup$ This isn't an answer, but as for your average Joe detecting it, no; I can see the four largest moons of Jupiter with my 10" Dobsonian Reflector (a "cheap" telescope). Europa just looks like a dot of light, but is waaaay larger than Phobos, and waaay further. $\endgroup$
    – Mikey
    Apr 24, 2015 at 18:44
  • $\begingroup$ The alien prohibition against doing this in a system where the indigenous life-forms have nukes is a good one - if they have nukes, they can build an Orion spaceship, and come out and nuke your gas station. 'Cannot do anything about it' is only relevant now, and doesn't mean 'Won't ever be able to do anything about it'. $\endgroup$
    – Monty Wild
    Oct 18, 2015 at 22:47
  • $\begingroup$ @MontyWild thats great comment! Makes great idea for a story. Thanks for it $\endgroup$ Oct 19, 2015 at 6:44

2 Answers 2


Given your parameters, Earth will discover this almost immediately (with a small lag due to the speed of light). The various signals emitted from the space bar, spacecraft, traffic regulation systems and so on will be picked up by sensitive astronomical radio telescopes, the Deep Space Network (which sends message traffic to and from various space probes, including the New Horizons probe nearing Pluto and the Voyager spacecraft exiting the solar system) and some of the military systems as well. In terms of nations who have access to these systems, this is effectively the United States and allied nations, Russia, China, the EU and India, roughly in that order.

If alien spacecraft follow regular Newtonian physics in space, then they will probably be using rockets, which can also be visible from great distances, especially in infrared wavelengths. Space telescopes will have little difficulty picking them out once focused on the region.

Oddly, any current Earthly spacecraft in the Jupiter system will have less ability to track and record these events, since the ground controllers will need fairly precise information to reprogram the orbits of these craft and point the cameras and other instruments at the Space Bar. Much of the problem is these space probes do not have powerful engines, and would need months of reprogramming and minor orbital adjustments to get into a series of orbital "slingshots" around the various moons to get in position (and even then is most likely to just be able to do a flypast).

Now while your question points out that we don't have any ability to do something about this now, I'm pretty sure once the situation becomes clear there will be a great deal of effort put into becoming able to do something; ranging from sending nasty cease and desist orders via radio to training battalions of Space Marines and building rockets that really are capable of delivering them to Jupiter (we have lots of theoretical and early prototype systems, mostly using nuclear fission energy, which can do the job, we just need to start bending metal and doing the advanced R&D to make them more affordable and efficient). The most fearsome weapons in our arsenals: legions of Space Lawyers, will likely arrive once the Marines have secured a landing zone. The Galactic Empire will tremble once they realize just what has been unleashed from Sol III!

  • $\begingroup$ Space lawyers may be scary, but not as scary as the engines which brought the aliens here in the first place. $\endgroup$
    – kasperd
    Oct 18, 2015 at 9:41

Jupiter is big enough and bright enough to be easily viewable with the naked eye from Earth. Perhaps as a result of this, it is a favorite target for amateur astronomers to train their backyard telescopes on.

In this time lapse, you can see Jupiter's moon Io transiting the planet; in the first few frames is when it is most visible as a bright circle of light against the black behind the planet.

Io is approximately 3,600 km in diameter, which makes it a bit more than 100 times larger than your Phobos-sized gas station. Keeping in mind that the image linked above is actually reduced by ~30% (at least according to the specs quoted by the original backyard astronomer who provided this image) and suffers some image quality degradation due to weather and the post-processing methods used, and that it would almost certainly have lights of its own and not just reflect that of the sun, I feel like the answer would be that yes, your gas station would be visible to (some, at least) backyard amateur astronomers (as a tiny point of light orbiting the planet), which means it would certainly be visible to the pros with their "big boy toys".

How long would it take to be spotted? Unless it's being towed into orbit fully-constructed, or construction is quick enough that it takes place entirely on the "dark side" of the planet, we'd see it dozens of times over before construction is even completed. That's not even considering the thermal blasts of rocket engines and heat signatures of hot spacecraft buzzing around the thing, or the radio signals in use.


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