Aliens hanging out in the Kuiper Belt? We could see the light from their cities

Aliens hanging out in the Kuiper Belt? we could see the light from their cities

When it comes to searching for ET, current efforts have been almost exclusively placed in picking up a radio signal – just a small portion of the electromagnetic spectrum. Consider for a moment just how much lighting we here on Earth produce and how our “night side” might appear as viewed from a telescope on another planet. If we can assume that alternate civilizations would evolve enjoying their natural lighting, wouldn’t it be plausible to also assume they might develop artificial lighting sources as well?

Is it possible for us to peer into space and spot artificially illuminated objects “out there?” According to a new study done by Abraham Loeb (Harvard), Edwin L. Turner (Princeton), the answer is yes.

For gathering light, the array of Earthly telescopes now at science’s disposal are able to confidently observe a light source comparable in overall brightness to a large city — up to a certain distance. Right now astronomers are able to measure the orbital parameters of objects (KBOs) with the greatest of precision by their observed flux and computing their changing orbital distances.

However, is it possible to see light if it were to occur on the dark side? Loeb and Turner say that current optical telescopes and surveys would have the ability to see this amount of light at the edge of our Solar System and observations with large telescopes can measure a KBOs spectra to determine if they are illuminated by artificial lighting using a logarithmic slope (sunlit object would exhibit alpha=(dlogF/dlogD) = -4, whereas artificially-illuminated objects should exhibit alpha = -2.)

“Our civilization uses two basic classes of illumination: thermal (incandescent light bulbs) and quantum (light emitting diodes [LEDs] and fluorescent lamps)” Loeb and Turn write in their paper. “Such artificial light sources have different spectral properties than sunlight. The spectra of artificial lights on distant objects would likely distinguish them from natural illumination sources, since such emission would be exceptionally rare in the natural thermodynamic conditions present on the surface of relatively cold objects. Therefore, artificial illumination may serve as a lamppost which signals the existence of extraterrestrial technologies and thus civilizations.”

Spotting this illumination difference in the optical band would be tricky but by calculating the observed flux from solar illumination on Kuiper Belt Objects with a typical albedo, the team is confident that existing telescopes and surveys could detect the artificial light from a reasonably brightly illuminated region, roughly the size of a terrestrial city, located on a KBO. Even though the light signature would be weaker, it would still carry the dead give-away – the spectral signature.

However, we currently don’t expect there to be any civilizations thriving at the edge of our solar system, as it is dark and cold out there.

But Loeb has posed that possibly planets ejected from other parent stars in our galaxy may have traveled to the edge of our Solar System and ended up residing there. Whether a civilization would survive an ejection event from their parent system, and then put up lamposts is up for debate, however.

The team isn’t suggesting that any random light source detected where there should be darkness might be considered a sign of life, though. There are many factors which could contribute to illumination, such as viewing angle, backscattering, surface shadowing, outgassing, rotation, surface albedo variations and more. this is just a new suggestion and a new way of looking at things, as well as suggested exercises for future telescopes and studying exoplanets.

“City lights would be easier to detect on a planet which was left in the dark of a formerly-habitable zone after its host star turned into a faint white dwarf,” Loeb and Turner say. “The related civilization will need to survive the intermediate red giant phase of its star. If it does, separating its artificial light from the natural light of a white dwarf, would be much easier than for the original star, both spectroscopically and in total brightness.”

The next generation of optical and space-based telescopes could help to refine the search process when observing extra-solar planets and preliminary broad-band photometric detection could be improved through the use of narrow-band filters which are tuned to the spectral features of artificial light sources such as light emitting diodes. While such a scenario on a distant world would need to involve far more “light pollution” than even we produce – why rule it out?

“This method opens a new window in the search for extraterrestrial civilizations,” Loeb and Turner write. “The search can be extended beyond the Solar System with next generation telescopes on the ground and in space, which would be capable of detecting phase modulation due to very strong artificial illumination on the night-side of planets as they orbit their parent stars.”

Explore further

City lights could reveal E.T. civilization

More information: Read Loeb and Turner’s paper: Detection Technique for Artificially-Illuminated Objects in the Outer Solar System and Beyond.

This article was inspired by a discussion on Google+

Source: Universe Today
Citation: Aliens hanging out in the Kuiper Belt? We could see the light from their cities (2011, December 19) retrieved 25 April 2019 from
This document is subject to copyright. Apart from any fair dealing for the purpose of private study or research, no part may be reproduced without the written permission. The content is provided for information purposes only.

Feedback to editors

User comments

Dec 19, 2011
Kuiper objects would seem rather cold to me, the aliens , if any, would probably not live on the surface, but underground near the comfy heat of their nuclear reactors, maybe there would be lightposts on the surface to illuminate mining activities, but it all seems a little far fetched...

Dec 19, 2011
Unlike the SETI scientists, aliens would likely be intelligent. Therefore they would likely settle in and around Earth, in this solar system. And of course, if you are paying attention, there is plenty of evidence that they have, and are.

Dec 19, 2011
Kuiper objects would seem rather cold to me,...

Yes, it said this in the article.

Personally, I think the whole point of the article is that as technology improves, seeing things like artificial illumination becomes more likely.

Dec 19, 2011
we have already received a signal from space. by my reckoning the signal source has to be about 36 (ish) light years away.
we broadcast a signal in early tests of radio waves. signal received and answered by late 80's.

why has there never been a deep search done of the area the signal originated?

Dec 19, 2011
@btb101: You mean the WOW! signal? we have been looking at those coordinates constantly for the last 30 years. Not a peep. The instrument that recorded it was not good enough to rule out all of the possible non-ETI causes. So either the aliens are teasing us, or it was not an ETI signal.

Dec 19, 2011
Why the aliens should occupy just the inhospitable Kuiper belt - until they're not complete trolls, indeed? It's just another attempt for sucking of the easy grant money from naive tax payers.

Dec 19, 2011
Yet another anthropocentric "study". The very first question to be asked is: would random non-anthropomorphic intelligent alien species use any artificial light? Most likely answer is no. There are many evolutionary reasons for such aliens not to need artificial light followed by socio/cultural practices that would lead to lack of use even in theoretical alien communities that may "need" it. Very similar to radio communications - many possible alien civilizations may not need it and from those who could use it - some may not want to... In all these cases we are limiting ourselves to search for particular cases very similar to us while we may be a rarity...

Dec 20, 2011
It's unlikely that any alien structures in our Kupier belt would likely have any significant external illumination. Waste of resources.
Why have windows when you can have viewscreens that can shift view, perform other display functions, and don't create an engineering weakness in your life sustaining enclosures.
As to streetlights, I don't really think anyone intends to go for casual strolls in the vacuum while worrying about not seeing the muggers in the dark alleys.
Headlights are a different story. You can be pretty sure that the sensor systems any of their vehicles would have aren't making any significant use of the em spectrum we can see with.

This idea of looking for city lights in the Kuiper belt is not well thought out in my opinion with regards to the realities of living out there. Then again, what do we really know about alien psychology and technology. Maybe they also make their spaceships out of paper. :)

Dec 20, 2011
According to Buddha(Supreme being who knew everything) there are totally 31 realms in the solar system.
But Science proved only two types from those which are human realm and animal realm.
Many living beings such as Asuras, Gods or Brahmas and their worlds are made of different kind of very soft matter which humans can't see.May be it has a different atomic structure than our chimerical elements. This maybe that kind of cities!!!

Dec 20, 2011
I think a lot of people on this post are missing the point. The two guys who conducted the study are pointing out that we have the capabilities of detecting faint light sources in the Kuiper belt. They are then saying that it is also possible to see lights in other solar systems. What this does is get some other bright people thinking about how to accomplish this. In a few years, some bright PhD candidate is going to publish his thesis about how to detect artificial lights on alien planets. Somewhere in not too many years, say less than 50, there'll be a new type of telescope, receiver array, etc. looking at these worlds for lights. The money was going to be wasted on something, it might as well be on something fun!

Dec 20, 2011
I agree with awab. Although this current experiment seems futile and a waste of time, the future uses and improvements could help us in the search for life in other systems. Given time, the continuous improvements in spectrometers, instruments that separate starlight into their component colors for analysis should help this search go further a field.

Please sign in to add a comment. Registration is free, and takes less than a minute. Read more