Researchers Just Scanned 14 Worlds From the Kepler Mission for “Technosignatures”, Evidence of Advanced Civilizations

When it comes to looking for life on extra-solar planets, scientists rely on what is known as the “low-hanging fruit” approach. In lieu of being able to observe these planets directly or up close, they are forced to look for “biosignatures” – substances that indicate that life could exist there. Given that Earth is the only planet (that we know of) that can support life, these include carbon, oxygen, nitrogen and water.

However, while the presence of these elements are a good way of gauging “habitability”, they are not necessarily indications that extra-terrestrial civilizations exist. Hence why scientists engaged in the Search for Extra-Terrestrial Intelligence (SETI) also keep their eyes peeled for “technosignatures”. Targeting the Kepler field, a team of scientists recently conducted a study that examined 14 planetary systems for indications of intelligent life.

The study, titled “A search for technosignatures from 14 planetary systems in the Kepler field with the Green Bank Telescope at 1.15-1.73 GHz“, recently appeared online and is being reviewed for publication by The Astronomical Journal. The team was led by Jean-Luc Margot, the Chair of the UCLA Department of Earth, Planetary, and Space Sciences (UCLA EPSS) and a Professor with UCLA’s Department of Physics and Astronomy.

The Green Bank Telescope is the world’s largest, fully-steerable telescope, which is currently being used in a new SETI (Search for Extraterrestrial Intelligence) attempt to look for possible alien radio signals from Tabby’s Star. Credit: NRAO/AUI/NSF

In addition to Margot, the team consisted of 15 graduate and undergraduate students from UCLA and a postdoctoral researcher from the Green Bank Observatory and the Center for Gravitational Waves and Cosmology at West Virginia University. All of the UCLA students participated in the 2016 course, “Search for Extraterrestrial Intelligence: Theory and Applications“.

Together, the team selected 14 systems from the Kepler catalog and examined them for technosignatures. While radio waves are a common occurrence in the cosmos, not all sources can be easily attributed to natural causes. Where and when this is the case, scientists conduct additional studies to try and rule out the possibility that they are a technosignature. As Professor Margot told Universe Today via email:

“In our article, we define a “technosignature” as any measurable property or effect that provides scientific evidence of past or present technology, by analogy with “biosignatures,” which provide evidence of past or present life.”

For the sake of their study, the team conducted an L-band radio survey of these 14 planetary systems. Specifically, they looked for signs of radio waves in the 1.15 to 1.73 gigahertz (GHz) range. At those frequencies, their study is sensitive to Arecibo-class transmitters located within 450 light-years of Earth. So if any of these systems have civilizations capable of building radio observatories comparable to Arecibo, the team hoped to find out!

Spring 2016 UCLA SETI class with Larry Lesyna. Credit: UCLA

“We searched for signals that are narrow (< 10 Hz) in the frequency domain,” said Margot. “Such signals are technosignatures because natural sources do not emit such narrowband signals… We identified approximately 850,000 candidate signals, of which 19 were of particular interest. Ultimately, none of these signals were attributable to an extraterrestrial source.”

What they found was that of the 850,000 candidate signals, about 99% of them were automatically ruled out because they were quickly determined to be the result of human-generated radio-frequency interference (RFI). Of the remaining candidates, another 99% were also flagged as anthropogenic because their frequencies overlapped with other known sources of RFI – such as GPS systems, satellites, etc.

The 19 candidate signals that remained were heavily scrutinized, but none could be attributed to an extraterrestrial source. This is key when attempting to distinguish potential signs of intelligence from radio signals that come from the only intelligence we know of (i.e. us!) Hence why astronomers have historically been intrigued by strong narrowband signals (like the WOW! Signal, detected in 1977) and the Lorimer Burst detected in 2007.

In these cases, the sources appeared to be coming from the Messier 55 globular cluster and the Large Magellanic Cloud, respectively. The latter was especially fascinating since it was the first time that astronomers had observered what are now known as Fast Radio Bursts (FRBs). Such bursts, especially when they are repeating in nature, are considered to be one of the best candidates in the search for intelligent, technologically-advanced life.

The UCLA SETI Group banner, featuring a photo of the central region of the Milky Way Galaxy. Credit: Yuri Beletsky/Carnegie Las Campanas Observatory

Unfortunately, these sources are still being investigated and scientists cannot attribute them to unnatural causes just yet. And as Professor Margot indicated, this study (which covered only 14 of the many thousand exoplanets discovered by Kepler) is just the tip of the iceberg:

“Our study encompassed only a small fraction of the search volume.  For instance, we covered less than five-millionths of the entire sky.  We are eager to scale the effort to sample a larger fraction of the search volume. We are currently seeking funds to expand our search.”

Between Kepler‘s first and second mission (K2), a total of 5,118 candidates and 2,538 confirmed exoplanets have been discovered within our galaxy alone. As of February 1st, 2018, a grand total of 3,728 exoplanets have been confirmed in 2,794 systems, with 622 systems having more than one planet. On top of that, a team of researchers from the University of Oklahoma recently made the first detection of extra-galactic planets as well!

It would therefore be no exaggeration to say that the hunt for ETI is still in its infancy, and our efforts are definitely beginning to pick up speed. There is literally a Universe of possibilities out there and to think that there are no other civilizations that are also looking for us seems downright unfathomable. To quote the late and great Carl Sagan: “The Universe is a pretty big place. If it’s just us, seems like an awful waste of space.”

And be sure to check out this video of the 2017 UCLA SETI Group, courtesy of the UCLA EPSS department:

Further Reading: arXiv

Exoplanet-Hunting Aliens Could Be Looking at Earth Right Now!

In the past few decades, the search for extra-solar planets has turned up a wealth of discoveries. Between the many direct and indirect methods used by exoplanet-hunters, thousands of gas giants, rocky planets and other bodies have been found orbiting distant stars. Aside from learning more about the Universe we inhabit, one of the main driving forces behind these efforts has been the desire to find evidence of Extra-Terrestrial Intelligence (ETI).

But suppose there are ETIs out there that are are also looking for signs of intelligence other than their own? How likely would they be to spot Earth? According to a new study by a team of astrophysicists from Queen’s University Belfast and the Max Planck Institute for Solar System Research in Germany, Earth would be detectable (using existing technology) from several star systems in our galaxy.

This study, titled “Transit Visibility Zones of the Solar System Planet“, was recently published in the Monthly Notices of the Royal Astronomical Society. Led by Robert Wells, a PhD student at the Astrophysics Research Center at Queen’s University Belfast, the team considered whether or not Earth would be detectable from other star systems using the Transit Method.

Diagram of a planet (e.g. the Earth, blue) transiting in front of its host star (e.g. the Sun, yellow). The lower black curve shows the brightness of the star noticeably dimming over the transit event, when the planet is blocking some of the light from the star. Credit: R. Wells.

This method consists of astronomers observing stars for periodic dips in brightness, which are attributed to planets passing (i.e. transiting) between them and the observer. For the sake of their study, Wells and his colleagues reversed the concept in order to determine if Earth would be visible to any species conducting observations from vantage points beyond our Solar System.

To answer this question, the team looked for parts of the sky from which one planet would be visible crossing the face of the Sun – aka. “transit zones”. Interestingly enough, they determined that the terrestrial planets that are closer to the Sun (Mercury, Venus, Earth and Mars) would easier to detect than the gas and ice giants – i.e.  Jupiter, Saturn, Uranus and Neptune.

While considerably larger, the gas/ice giants would be more difficult to detect using the transit method because of their long-period orbits. From Jupiter to Neptune, these planets take about 12 to 165 years to complete a single orbit! But more important than that is the fact that they orbit the Sun at much greater distances than the terrestrial planets. As Robert Wells indicated in a Royal Astronomical Society press statement:

”Larger planets would naturally block out more light as they pass in front of their star. However the more important factor is actually how close the planet is to its parent star – since the terrestrial planets are much closer to the Sun than the gas giants, they’ll be more likely to be seen in transit.”

How the transit zone of a Solar System planet is projected out from the Sun. The observer on the green exoplanet is situated in the transit zone and can therefore see transits of the Earth. Credit: R. Wells

Ultimately, what the team found was that at most, three planets could be observed from anywhere outside of the Solar System, and that not all combinations of these three planets was possible. For the most part, an observer would see only planet making a transit, and it would most likely be a rocky one. As Katja Poppenhaeger, a lecturer at the School of Mathematics and Physics at Queen’s University Belfast and a co-author of the study, explained:

“We estimate that a randomly positioned observer would have roughly a 1 in 40 chance of observing at least one planet. The probability of detecting at least two planets would be about ten times lower, and to detect three would be a further ten times smaller than this.”

What’s more, the team identified sixty-eight worlds where observers would be able to see one or more of the Solar planets making transits in front of the Sun. Nine of these planets are ideally situated to observe transits of the Earth, though none of them have been deemed to be habitable. These planets include HATS-11 b, 1RXS 1609 b, LKCA 15 b, WASP-68 b, WD 1145+017 b, and four planets in the WASP-47 system (b, c, d, e).

On top of that, they estimated (based on statistical analysis) that there could be as many as ten undiscovered and potentially habitable worlds in our galaxy which would be favorably located to detect Earth using our current level of technology. This last part is encouraging since, to date, not a single potentially habitable planet has been discovered where Earth could be seen making transits in front of the Sun.

Image showing where transits of our Solar System planets can be observed. Each line represents where one of the planets could be seen to transit, with the blue line representing Earth; an observer located here could detect us. Credit: 2MASS/A. Mellinger/R. Wells.

The team also indicated that further discoveries made by the Kepler and K2 missions will reveal additional exoplanets that have “a favorable geometric perspective to allow transit detections in the Solar System”. In the future, Wells and his team plan to study these transit zones to search for exoplanets, which will hopefully reveal some that could also be habitable.

One of the defining characteristics in the Search for Extra-Terrestrial Intelligence (SETI) has been the act of guessing about what we don’t know based on what we do. In this respect, scientists are forced to consider what extra-terrestrial civilizations would be capable of based on what humans are currently capable of. This is similar to how our search for potentially habitable planets is limited since we know of only one where life exists (i.e. Earth).

While it might seem a bit anthropocentric, it’s actually in keeping with our current frame of reference. Assuming that intelligent species could be looking at Earth using the same methods we do is like looking for planets that orbit within their star’s habitable zones, have atmospheres and liquid water on the surfaces.

In other words, it’s the “low-hanging fruit” approach. But thanks to ongoing studies and new discoveries, our reach is slowly extending further!

Further Reading: RAS, MNRAS

Breakthrough Detects Repeating Fast Radio Bursts Coming from Distant Galaxy

In July of 2015, Russian billionaire Yuri Milner announced the creation of Breakthrough Listen, a decade-long project that would conduct the largest survey to date for signs of extra-terrestrial communications (ETI). As part of his non-profit organization, Breakthrough Initiatives, this survey would rely on the latest in instrumentation and software to observe the 1,000,000 closest stars and 100 closest galaxies.

Using the Green Bank Radio Telescope in West Virginia, the Listen science team at UC Berkeley has been observing distant stars for over a year now. And less than a week ago, they observed 15 Fast Radio Bursts (FRBs) coming from a dwarf galaxy located three billion light-years away. According to a study that described their findings, this was the first time that repeating FRBs have been seen coming from this source at these frequencies.

The team’s study, titled “FRB 121102: Detection at 4 – 8 GHz band with Breakthrough Listen backend at Green Bank“, was recently published in The Astronomers Telegraph. Led by Dr. Vishal Gajjar – a postdoctoral researcher at the University of California, Berkeley – the team conducted a detailed survey of FRB 121102. This repeating FRB source is located in a dwarf galaxy in Auriga constellation, some 3 billion light-years from Earth.

The NSF’s Arecibo Observatory, which is located in Puerto Rico, is the world largest radio telescope. Credit: NAIC

To clarify, FRBs are brief, bright pulses of radio waves that are periodically detected coming from distant galaxies. This strange astronomical phenomena was first detected in 2007 by Duncan Lorimer and David Narkovic using the Parkes Telescope in Australia. To honor their discovery, FRBs are sometimes referred to as “Lorimer Bursts”. Many FRB sources have been confirmed since then, some of which were found repeating.

The source known as FRB 121101 was discovered back on November 2nd, 2012, by astronomers using the Arecibo radio telescope. At the time, it was the first FRB to be discovered; and by 2015, it became the first FRB to be seen repeating. This effectively ruled out the possibility that repeating FRBs were caused by catastrophic events, which had previously been theorized.

And in 2016, FRB 121102 was the first FRB to have its location pinpointed to such a degree that its host galaxy could be identified. As such, the Listen science team at UC Berkeley was sure to add FRB 121102 to their list of targets. And in the early hours of Saturday, August 26th, Dr. Vishal Gajjar – a postdoctoral researcher at UC Berkeley – observed FRB 121102 using the Green Bank Radio Telescope (GBRT) in West Virginia.

Using the Digital Backend instrument on the GBRT, Dr. Gajjar and the Listen team observed FRB 121102 for five hours. From this, they accumulating 400 terabytes of data in the entire 4 to 8 GHz frequency band which they then analyzed for signs of short pulses over a broad range of frequencies. What they found was evidence of 15 new pulses coming from FRB 121102, which confirmed that it was in a newly active state.

The Green Bank Telescope, located in West Virginia. Credit: NRAO

In addition, their observations revealed that the brightest of these 15 emissions occurred at around 7 GHz. This was higher than any repeating FRBs seen to date, which indicated for the first time that they can occur at frequencies higher than previously thought. Last, but not least, the high-resolution data the Listen team collected is expected to yield valuable insights into FRBs for years to come.

This was made possible thanks to the Digital Backend instrument on the GBRT, which is able to record several GHz of bandwidth simultaneously and split the information into billions of individuals channels. This enables scientists to study the proprieties and the frequency spectrum of FRBs with greater precision, and should lead to new theories about the causes of these radio emissions.

So even if these particular signals should prove to not be an indication of extra-terrestrial intelligence, Listen is still pushing the boundaries of what is possible with radio astronomy. And given that Breakthrough Listen is less than two years into its proposed ten-year survey, we can expect many more sources to be observed and studied in the coming years. If there’s evidence of ETI to be found, we’re sure to find out about it sooner or later!

And be sure to check out this video of the Green Bank Telescope and the surveys it allows for, courtesy of Berkeley SETI:

Further Reading: Breakthrough Initiatives

Advanced Civilizations Could Build a Galactic Internet with Planetary Transits

In a series of papers, Professor Loeb and Michael Hippke indicate that conventional rockets would have a hard time escaping from certain kinds of extra-solar planets. Credit: NASA/Tim Pyle

Decades after Enrico Fermi’s uttered his famous words – “Where is everybody?” – the Paradox that bears his name still haunts us. Despite repeated attempts to locate radio signals coming from space and our ongoing efforts to find visible indications of alien civilizations in distant star systems, the search extra-terrestrial intelligence (SETI) has yet to produce anything substantive.

But as history has taught us, failure has a way of stimulated new and interesting ideas. For example, in a recently-published paper, Dr. Duncan H. Forgan of St. Andrews University proposed that extra-terrestrial civilizations could be communicating with each other by creating artificial transits of their respective stars. This sort of “galactic internet” could be how advanced species are attempting to signal us right now.

Forgan’s paper, “Exoplanet Transits as the Foundation of an Interstellar Communications Network“, was recently published online. In addition to being a research fellow at the School of Physics and Astronomy and the Scottish Universities Physics Alliance at the University of St Andrews (Scotland’s oldest academic institution), he is also a member of the St Andrews Center for Exoplanet Science.

The paper begins by addressing the two fundamental problems associated with interstellar communication – timing and energy consumption. When it comes to things like radio transmissions, the amount of energy that would be needed to transmit a coherent message over interstellar distances is prohibitive. Optical communications (i.e. lasers) need less energy, but spotting them would require incredibly precise timing.

As such, neither method would be particularly reliable for establishing an interstellar communications system. Taking a cue from humanity’s recent exoplanet-hunting efforts, Forgan argues that a method where transits in front of a stars are a basis of communication would solve both problems. The reason for this is largely due to the fact that the Transit Method is currently one of the most popular and reliable ways of detecting exoplanets.

By monitoring a star for periodic dips in brightness, which are caused by a planet or object passing between the observer and the star, astronomers are able to determine if the star has a system of planets. The method is also useful for determining the presence and composition of atmospheres around exoplanet. As Forgan indicates in the paper, this method could therefore be used as a means of signalling other civilizations:

“An ETI ’A’ can communicate with ETI ’B’ if B is observing transiting planets in A’s star system, either by building structures to produce artificial transits observable by B, or by emitting signals at B during transit, at significantly lower energy consumption than typical electromagnetic transmission schemes.”
The Milky Way’s habitable zone. Credit: NASA/Caltech

In short, Forgan argued that within the Galactic Habitable Zone (GHZ) – the region of the Milky Way in which life is most likely develop – species may find that the best way to communicate with each other is by creating artificial megastructures to transit their star. These transits, which other civilizations will be looking for (looking for exoplanets, like us!) will lead them to conclude that an advanced civilization exists in another star system.

He even offers estimates on how often such transmissions could be made. As he put it:

“A message with a path of 20 kpc (the diameter of the GHZ) has a total travel time at lightspeed of just under 0.06 Myr. If we assume a relatively short timescale on which both ETIs remain in the transit zone of 100,000 years (which is approaching the timescale on which both secular evolution of planetary orbits and the star’s orbit become important), then a total of 30 exchanges can be made. This of course does not forbid a continuing conversation by other means.”

If this is starting to sound familiar, that’s probably because this is precisely what some theorists say is happening around KIC 8462852 (aka. Tabby’s Star). Back in May of 2015, astronomers noticed that the star had been undergoing considerable drops in brightness in the past few years. This behavior confounded natural explanations, which led some to argue that it could be the result of an alien megastructure passing in front of the star.

According to Forgan, such a possibility is hardly far-fetched, and would actually be a relatively economical means of communicating with other advanced species. Using graph theory, he estimated that civilizations within the GHZ could establish a fully connected network within a million years, where all civilizations are in communication with each other (either directly or via intermediate civilizations).

Artist’s concept of KIC 8462852, which has experienced unusual changes in luminosity over the past few years. Credit: NASA, JPL-Caltech

Not only would this network require far less energy to transmit data, but the range of any signal would be limited only by the extent of these civilizations themselves. Beyond saving energy and having greater range (assuming intermediate civilizations are able to pass messages along), this method presents other advantages. For one, a high level of technological sophistication would be required to pick up the transit of exoplanets.

In other words, civilizations would need to reach a certain level of development before they could hope to join the network. This would prevent any unfortunate “cultural contamination”, where less-advanced civilizations learned about the existence of aliens before they were ready. Second, once acquired, the transit network signals would be extremely predictable, with each transmission corresponding to a known orbital period.

That being said, there are some downsides that Forgan was sure to acknowledge. For starters, the periodicity of these signals would be a double edged sword, as signals could only be sent if and when the receiver begins to see the transit. And while a megastructure could be moved to alter the transit period, this poses problems in terms of synchronizing transmission and reception.

Addressing the limitations of the analysis, Forgan also acknowledges that the study relies on fixed stellar orbits. The orbits of stars are known to change over time, with stars passing in and out of the GHZ regularly on cosmic timescales. In addition, there is also the issue of how such a network would differ between denser regions in the galaxy – i.e. globular clusters – and areas populated by field stars. Binary stars are also not considered in the analysis.

Could alien megastructures be the key to interstellar communications? Credit: Kevin Gill

In addition, planetary orbits are known to change over time, due to perturbations caused by neighboring planets, companion stars, or close encounters with passing stars. As a result, the visibility of transiting planets can vary even more over cosmic timescales. Last, but not least, the study assumes that civilizations have a natural lifespan of about a billion years, which is not based in any concrete knowledge.

However, these considerations do not alter the overall conclusions reached by Forgan. Making allowances for the dynamic nature of stars and planets, and assuming that civilizations exist for only 1 million years, Forgan maintains that the creation of an interstellar network of this kind is still mathematically feasible. On top of that, an artificial object could continue to signal other species long after a civilization has gone extinct.

Addressing the Fermi Paradox, Forgan concludes that this sort of communication would take a long time to detect.As he summarizes in the paper (bold added for emphasis):

“I find that at any instant, only a few civilizations are correctly aligned to communicate via transits. However, we should expect the true network to be cumulative, where a “handshake” connection at any time guarantees connection in the future via e.g. electromagnetic signals. In all our simulations, the cumulative network connects all civilizations together in a complete network. If civilizations share knowledge of their network connections, the network can be fully complete on timescales of order a hundred thousand years. Once established, this network can connect any two civilizations either directly, or via intermediate civilizations, with a path much less than the dimensions of the GHZ.”

In short, the reason we haven’t heard from or found evidence of ETI could be an issue of timing. Or, it could be that we simply didn’t realize we were being communicated with. While such an analysis is subject to guess-work and perhaps a few anthropocentric assumptions, it is certainly fascinating because of the possibilities it presents. It also offers us a potential tool in the search for extra-terrestrial intelligence (SETI), one which we are already engaged in.

So many stars, so many planets. So many opportunities for connection! Credit: ESO/M. Kornmesser

And last, but not least, it offers a potential resolution to the Fermi Paradox, one which we may have already stumbled upon and are simply not yet aware of. For all we know, the observed drops in brightness coming from Tabby’s Star are evidence of an alien civilization (possibly an extinct one). Of course, the key word here is “perhaps”, as no evidence exists that could confirm this.

The possibilities raised by this paper are also exciting given that exoplanet-hunting is expected to ramp up in the coming years. With the deployment of next-generations missions like the James Webb Space Telescope and the Transiting Exoplanet Survey Satellite (TESS), we expect to be learning a great deal more about star systems both near and far.

Will we find more examples of unexplained drops in brightness? Who knows? The point is, if we do (and can’t find a natural cause for them) we have a possible explanation. Maybe its neighbors inviting us to “log on”!

Further Reading: arXiv

Maybe the Aliens Aren’t Hiding, they’re Sleeping, Waiting for the Universe to Get Better

When you consider that age of the Universe – 13.8 billion years by our most recent counts –  and that which is “observable” to us measures about 93 billion light years in diameter, you begin to wonder why we haven’t found signs of extra-terrestrial intelligence (ETI) beyond our Solar System. To paraphrase Enrico Fermi, the 20th century physicists who advanced the famous Fermi Paradox – “where the heck are all the aliens?”

Naturally, Fermi’s Paradox has attracted a lot of theoretical explanations over the years – which include ETI being very rare, humanity being early to the Universe, and the aliens being extinct! But a new study by a team of scientists from the Future of Humanity Institute (FHI) offers a different take on this age-old paradox. According to their study, the key to answering this question is to consider the possibility that the aliens are engaged in “aestivation”.

Essentially, aestivation is a prolonged state of torpor that organisms enter into during a particularly hot or dry period. Similar to what hibernating animals do during the winter, this state is designed to keep creatures alive until more favorable conditions emerge. And when applied to the cosmos, this concept could explain why one of the key things astronomers have been looking for – i.e. activity – has been lacking.

The study was led by Anders Sandberg, a research associate to the Oxford Uehiro Center for Practical Ethics, the Oxford Center for Neuroethics, and the James Martin Research Fellow at FHI. Cryptically titled, “That is Not Dead Which Can Eternal Lie: the Aestivation Hypothesis for Resolving Fermi’s Paradox“, their study considers the possibility that advanced alien civilizations might be difficult to find because they are sleeping right now.

This is not the first time Sandberg has addressed questions arising out of the Fermi Paradox. In a previous study, he and Stuart Armstrong (also a research associate with the FHI and one of the co-authors on this study) extended the Fermi Paradox to look beyond our own galaxy, addressing how more advanced civilizations would feasibly be able to launch colonization projects with relative ease (and even travel between galaxies without difficulty).

In the end, they concluded that civilizations from millions of galaxies should have been able to reach us by now, which only serves to bring the Fermi Paradox into greater focus. If these early civilizations are around, why are they not visible to us? The reason for this, they claim in this new study, has to do with the thermodynamics of computation.

According to this basic rule, the cost of a certain amount of computation is proportional to the temperature it generates. For some time, astronomers and cosmologists have been aware that the Universe is steadily cooling down over the time. Not only is star formation in galaxies slowly dying out over the course of billions of years, but even the cosmic background radiation is becoming colder.

Artist’s conception of city lights on an alien planet. Credit: David A. Aguilar (CfA)

As such, it makes sense that ancient and advanced civilizations would want to wait for cooler conditions to prevail. Sandberg explained to Universe Today via email:

“The core idea is that if advanced civilizations mainly or solely care about computation, then it is rational for them to wait until the Universe is much older than now. The reason is that the energy cost (which will eventually limit how much computation you can do) is proportional to temperature, and this means that the far future is vastly more hospitable than the hot present. If this were true, we have a nice explanation for the apparent absence of big old civilizations. It would also lead to observable consequences: a reduction in processes that waste resources they would want in the late eras.”

Timing is a key feature to this hypothesis. Much like the theory that humanity may have arrived early to the Universe, this theory states that the lack of detection has to do with species being in different places in their biological/technological evolution. In this case, the aestivation period of early civilizations has coincided with the subsequent rise of humanity as an space-faring and technologically-adept species.

Herein lies another reason why ancient civilizations might want to take a cosmic nap. Given how long life needs in order to emerge – humanity took roughly 4.5 billion years to get to where it is today – then it stands to reason that ancient civilizations might want to skip ahead a few eons in order to let new races emerge.

Ever since it was first announced in 2015, there has been speculation as to what could account for the dimming of KIC 8462852. Credit: SentientDevelopments.com

“There is an entropy cost to irreversible logical operations, including error correction,” said Sanders. “So unless there is some magical energy source or entropy sink, if you want to do as much computation as possible you should wait until the cosmic background radiation levels off. In addition, civilizations may want to go to the future if they want to meet other, independently evolved civilizations. If intelligence is rare in time and space but aestivates to the far future, then it will meet there.”

Of course, the aestiation hypothesis (much like the Drake Equation and the Fermi Paradox) is based on a few assumptions about what ETI would be capable of. These include:

  1. There are civilizations that mature much earlier than humanity.
  2. These civilizations can expand over sizeable volumes, gaining power over their contents.
  3. These civilizations have solved their coordination problems.
  4. A civilization can retain control over its volume against other civilizations.
  5. The fraction of mature civilizations that aestivate is non-zero
  6. Aestivation is largely invisible.

In other words, the hypothesis assumes the existence of civilizations that are more advanced than humanity which is based on the notion that they have had billions of years to develop elsewhere in the Universe. These civilizations would be higher on the Kardashev Scale (between Level II and III) by now, meaning that they had evolved to the point where they could harness the energy of entire star systems and perhaps even galaxies.

Also, it assumes that these civilizations would have become space-faring races that had expanded to occupy parts of the cosmos that lie well beyond their own star systems. Ultimately, those civilizations that have chosen to become dormant would therefore be invisible to us since they are not currently traveling between stars and galaxies, smashing up planets to create megastructures, or consuming entire stars for fuel.

You know, the kind of stuff we think mega-civilizations would do. Which naturally raises the question, how might we be able to detect such civilizations at rest? To this, Sandberg has a few possible suggestions, ones which ETI-hunters may want to heed:

“Look for galaxies that either move out of the way of galaxy collisions or towards big clusters by ejecting mass or energy in one direction, or have an unusually low number of heavy blue-white stars, or otherwise avoid losing gas to interstellar space. Or, try launching a self-replicating space probe to pave the universe and see if somebody stops you.”

As with all things having to do with aliens and ETI, a measure of guess-work is required here. And some would naturally argue that it is also possible that advanced civilizations are not subject to the same limitations we humans are, which would limit our ability to speculate here. In the end, we humans are required to theorize about what we don’t know based on what we do – aka. the “low-hanging fruit” approach.

The findings reported in the study were also the subject of a talk that took place at the second annual meeting of the UK SETI Research Network (UKSRN), which took place on September 11th and 12th, 2014, at Birkbeck College in London.

Further Reading: arXiv

Are Aliens Communicating with Neutrino Beams?

It is no easy thing to search for signs of intelligent life beyond our Solar System. In addition to the incredible distances involved and the fact that we really only have indirect methods at our disposal, there is also the small problem of not knowing exactly what to look for. If intelligent life does exist beyond our Solar System, would they even communicate as we do, using radio transmitters and similar forms of technology?

Such has been the preoccupation of groups like the Search for Extra Terrestrial Intelligence (SETI) Institute and, more recently, organizations like Messaging Extraterrestrial Intelligence (METI) International. A non-profit dedicated to communicating with extra-terrestrial intelligence (ETI), the organization recently suggested that looking for neutrinos and other exotic particles could help us find signals as well.

First, some clarification should be made as to what SETI and METI are all about it and what sets them apart. The term METI was coined by Russian scientist Alexander Zaitsev, who sought to draw a distinction between SETI and METI. As he explained in a 2006 paper on the subject:

“The science known as SETI deals with searching for messages from aliens. METI science deals with the creation of messages to aliens. Thus, SETI and METI proponents have quite different perspectives. SETI scientists are in a position to address only the local question “does Active SETI make sense?” In other words, would it be reasonable, for SETI success, to transmit with the object of attracting ETI’s attention? In contrast to Active SETI, METI pursues not a local and lucrative impulse, but a more global and unselfish one – to overcome the Great Silence in the Universe, bringing to our extraterrestrial neighbors the long-expected annunciation ‘You are not alone!'”

One of the 42 dishes in the Allen Telescope Array that searches for signals from space. Credit: Seth Shostak/SETI Institute.

In short, METI looks for ways in which we might be able to contact aliens instead of waiting to hear from them. However, this does not mean that organizations like METI International are without ideas on how me might better listen to our (potential) alien neighbors. After all, communication goes beyond mere messages, and also requires that a medium exist with which to convey the message.

Such is the recommendation put forth by Dr. Morris Jones, a space analyst and writer who serves on the METI advisory council. In a recent article published on METI International’s website, he addressed the two main challenges when it comes to looking for ETI. On the one hand, you have the need for multiple methodologies to increase the odds of finding something. But as he indicates, there’s also the problem of knowing what to look for:

“We are not really sure of how extraterrestrials would communicate with us. Would they use radio waves, lasers, or something more exotic? Perhaps the universe is awash in extraterrestrial signals that we cannot even receive. SETI and METI practitioners spend a lot of time wondering how a message would be encoded in terms of language and content. It’s also important to consider the medium of transmission.”

In the past, says Jones, SETI searches were based on radio astronomy because that was the only practical means of doing so. Since then, efforts have expanded to include optical telescopes and the search for laser signals. This is due to the fact that in the past few decades, human beings have developed the technology to use laser for the sake of communications.

An artist’s illustration of a light-sail powered by a radio beam (red) generated on the surface of a planet. Could the part of the beam that misses the sail be our mysterious Fast Radio Bursts? Image Credit: M. Weiss/CfA

In a 2016 SETI paper, Dr. Philip Lubin of the University of California, Santa Barbara, explained how the development of directed-energy propulsion could help us search for evidence of aliens. As one of the scientific minds behind Breakthrough Starshot – a laser-driven lightsail that would be fast enough to make the trip to Alpha Centauri in just 20 years – he believes it’s a safe bet that ETI could be using similar technology to travel or communicate.

In addition, Dr. Avi Loeb from the Harvard-Smithsonian Center for Astrophysics (also one of the minds behind Starshot) has also suggested that fast-radio bursts (FRBs) could be evidence of alien activity. FRBs have been a subject of fascination to scientists since they were first detected in 2007 (the “Lorimer Burst“), and could also be a sign of alien communications or a means of propulsion.

Another means involves searching for artefacts – i.e. looking for evidence of physical infrastructure in other star systems. Case in point, since 2015, astronomers have been seeking to determine what is responsible for the periodic dimming of KIC 8462852 (aka. Tabby’s Star). Whereas most studies have sought to explain this in terms of natural causes, others have suggested it could be evidence of an alien megastructure.

To this array of search methods, Dr. Jones offers a few other possibilities. One way is to look for neutrinos, a type of subatomic particle that is produced by the decay of radioactive elements and interacts with matter very weakly. This allows them to pass through solid matter and also makes them very difficult to detect. Neutrinos are produced in large quantities by our Sun and astronomical sources, but they can also be produced artificially by nuclear reactors.

Ever since it was first announced in 2015, there has been speculation as to what could account for the dimming of KIC 8462852. Credit: SentientDevelopments.com

These, claims Jones, could be used for the sake of communications. The only problem is that looking for them would require some specialized equipment. Currently, all means of detecting neutrinos involve expensive facilities that have to be built either underground or in extremely isolated locations to ensure that they are not subject to any kind of electromagnetic interference.

These include the Super-Kamiokande facility, the world’s largest neutrino detector which is located under Mt. Ikeno in Japan. There’s also the IceCube Neutrino Observatory, located at the Amundsen–Scott South Pole Station in Antarctica and operated by the University of Wisconsin–Madison; and the Sudbury Neutrino Observatory, located in a former mine complex near Sudbury, Ontario, and operated by SNOLAB.

Another possibility is searching for evidence of communications that rely on gravitational waves. Predicted by Einstein’s Theory of General Relativity, the first detection of these mysterious waves was first made in February 2016. And in the coming years and decades, it is expected that gravitational wave observatories will be established so the presence of these “ripples” in spacetime can be visualized.

However, compared to neutrinos, Jones admits that this seems like a long shot. “It’s hard to conceive with our current grasp of physics,” he writes. “They are extremely difficult to generate at a detectable level. You would need abilities similar to those of superheroes, and be able to smash neutron stars and black holes together at will. There are probably easier ways to get a message across the stars.”

Breakthrough Listen will monitor the 1 million closest stars to Earth over a ten year period. Credit: Breakthrough Initiatives

Beyond these, there is the even more exotic possibility of “Zeta Rays”, which Dr. Jones is not prepared to rule out. Basically, “Zeta Rays” is a term used by physicists to describe physics that go beyond the Standard Model. As scientists are currently looking for evidence of new particles with the Large Hadron Collider and other particle accelerators, it stands to reason that anything they discover will be the added to the SETI and METI search manifest.

But could such physics entail new forms of communication? Hard to say, but definitely worth considering. After all, the physics that power our current technology certainly existed before we did. Or as Jones put it:,

“Is it possible to transmit with something better than we already have? Until we know a lot more physics, we just won’t know. Humanity in the twenty-first century could be like an isolated tribe in the Amazon jungle a century ago, unaware that the air around them was filled with radio signals. SETI uses the science and technology provided to us by other disciplines. Thus, we must wait until physics itself makes some more major breakthroughs. Only then can we consider such exotic methods of searching. We think a lot about the message. But we should also think about the medium.”

Other projects that are dedicated to METI include Breakthrough Listen, a ten-year initiative launched by Breakthrough Initiatives to conduct the largest survey to date for extraterrestrial communications – encompassing the 1,000,000 closest stars and 100 closest galaxies. Back in April of 2017, the scientists behind this project shared their analysis of the first year of Listen data. No definitive results have been announced yet, but they are just getting started!

Ever since Drake proposed his famous equation, human beings have eagerly sought to find evidence of extra-terrestrial intelligence. Unfortunately, all of our efforts have been haunted by Fermi’s equally-famous paradox! But of course, as space exploration goes, we’ve really only begun to scratch the surface of our Universe. And the only way we can ever expect to find evidence of intelligent life out there is to keep looking.

And with greater knowledge and increasingly sophisticated methods at our disposal, we can be sure that if intelligent life is out there somewhere, we will find it eventually. One can always hope, right? And be sure to check out this video of Dr. Jones 2014 presentation at the SETI Institute, titled “A Journalistic Perspective on SETI-Related Message Composition“:

Further Reading: METI