An artist's illustration of a light-sail powered by a radio beam (red) generated on the surface of a planet. The leakage from such beams as they sweep across the sky would appear as Fast Radio Bursts (FRBs), similar to the new population of sources that was discovered recently at cosmological distances.
Credit: M. Weiss/CfA
When it comes to the challenges posed by interstellar travel, there are no easy answers. The distances are immense, the amount of energy needed to make the journey is tremendous, and the time scales involved are (no pun!) astronomical. But what if there was a way to travel between stars using ships that take advantage of natural phenomena to reach relativistic velocities (a fraction of the speed of light).
Already, scientists have identified situations where objects in our Universe are able to do this – including hypervelocity stars and meteors accelerated by supernovae explosions. Delving into this further, Harvard professors Manasvi Lingam and Abraham Loeb recently explored how interstellar spacecraft could harness the waves produced by a supernova explosion in the same way that sailing ships harness the wind.
Last week (Friday. Feb. 14th), the Breakthrough Listen Initiative released about 2 petabytes of optical and radio data that they have accumulated over the past four years. This is the second data release by the non-profit effort (as part of Breakthrough Initiatives) and the public is once again invited to search through the data for possible signs of extraterrestrial communications.
Planets everywhere. So where are all the aliens? Credit: ESO/M. Kornmesser
This week, the non-profit research organization Breakthrough Listen announced that it was entering into a partnership with scientists from the NASA Transiting Exoplanet Survey Satellite (TESS) mission. This new collaboration will direct the resources of the former with data and expertise of the latter to the search for extra-terrestrial intelligence (SETI) like never before!
One of the Daya Bay detectors.
Roy Kaltschmidt, Lawrence Berkeley National Laboratory
In 1960, famed theoretical physicist Freeman Dyson made a radical proposal. In a paper titled “Search for Artificial Stellar Sources of Infrared Radiation” he suggested that advanced extra-terrestrial intelligences (ETIs) could be found by looking for signs of artificial structures so large, they encompassed entire star systems (aka. megastructures). Since then, many scientists have come up with their own ideas for possible megastructures.
Like Dyson’s proposed Sphere, these ideas were suggested as a way of giving scientists engaged in the Search for Extra-Terrestrial Intelligence (SETI) something to look for. Adding to this fascinating field, Dr. Albert Jackson of the Houston-based technology company Triton Systems recently released a study where he proposed how an advanced ETI could use rely on a neutron star or black hole to focus neutrino beams to create a beacon.
Illustration of the supermassive black hole at the center of the Milky Way. It's huge, with over 4 times the mass of the Sun. But ultramassive black holes are even more massive and can contain billions of solar masses. Image Credit:
Credit: NRAO/AUI/NSF
In the course of looking for possible signs of Extra-Terrestrial Intelligence (ETI), scientists have had to do some really outside-of-the-box thinking. Since it is a foregone conclusion that many ETIs would be older and more technologically advanced than humanity, those engaged in the Search for Extra-Terrestrial Intelligence (SETI) have to consider what a more advanced species would be doing.
A particularly radical idea that has been suggested is that spacefaring civilizations could harness radiation emitted from black holes (Hawking radiation) to generate power. Building on this, Louis Crane – a mathematician from Kansas State University (KSU) – recently authored a study that suggests how surveys using gamma telescopes could find evidence of spacecraft powered by tiny artificial black holes.
Artist’s impression of the surface of the planet Proxima b orbiting the red dwarf star Proxima Centauri. The double star Alpha Centauri AB is visible to the upper right of Proxima itself. Credit: ESO
In recent years, the number of extra-solar planets discovered around nearby M-type (red dwarf stars) has grown considerably. In many cases, these confirmed planets have been “Earth-like“, meaning that they are terrestrial (aka. rocky) and comparable in size to Earth. These finds have been especially exciting since red dwarf stars are the most common in the Universe – accounting for 85% of stars in the Milky Way alone.
Unfortunately, numerous studies have been conducted of late that indicate that these planets may not have the necessary conditions to support life. The latest comes from Harvard University, where postdoctoral researcher Manasvi Lingam and Professor Abraham Loeb demonstrate that planets around M-type stars may not get enough radiation from their stars for photosynthesis to occur.
Artist's impression of a Dyson Sphere. The construction of such a massive engineering structure would create a technosignature that could be detected by humanity. Credit: SentientDevelopments.com/Eburacum45
In 1961, famed astronomer Frank Drake created a formula for estimating the number of extra-terrestrial intelligences (ETIs) that could exist within our galaxy. Known as the “Drake Equation“, this formula demonstrated that even by the most conservative estimates, our galaxy was likely to host at least a few advanced civilizations at any given time. About a decade later, NASA officially kicked of its search for extra-terrestrial intelligence (SETI) program.
These efforts have experienced a major infusion of interest in recent decades thanks to the discovery of thousands of extrasolar planets. To address the possibility that life may exist out there, scientists are also relying on sophisticated tools to search for telltale indicators of biological processes (aka. biosignatures) and technological activity (technosignatures), which could indicate not only life but advanced intelligence.
Project Starshot, an initiative sponsored by the Breakthrough Foundation, is intended to be humanity's first interstellar voyage. Credit: breakthroughinitiatives.org
On October 19th, 2017, the Panoramic Survey Telescope and Rapid Response System-1 (Pan-STARRS-1) in Hawaii announced the first-ever detection of an interstellar asteroid, named 1I/2017 U1 (aka. ‘Oumuamua). In the months that followed, multiple follow-up observations were conducted that allowed astronomers to get a better idea of its size and shape, while also revealing that it had the characteristics of both a comet and an asteroid.
Interestingly enough, there has also been some speculation that based on its shape, ‘Oumuamua might actually be an interstellar spacecraft (Breakthrough Listen even monitored it for signs of radio signals!). A new study by a pair of astronomers from the Harvard Smithsonian Center for Astrophysics (CfA) has taken it a step further, suggesting that ‘Oumuamua may actually be a light sail of extra-terrestrial origin.
This illustration shows the evolution of the Universe, from the Big Bang on the left, to modern times on the right. Image: NASA
During the 1930s, astronomers came to realize that the Universe is in a state of expansion. By the 1990s, they realized that the rate at which it is expansion is accelerating, giving rise to the theory of “Dark Energy”. Because of this, it is estimated that in the next 100 billion years, all stars within the Local Group – the part of the Universe that includes a total of 54 galaxies, including the Milky Way – will expand beyond the cosmic horizon.
At this point, these stars will no longer be observable, but inaccessible – meaning that no advanced civilization will be able to harness their energy. Addressing this, Dr. Dan Hooper – an astrophysicist from the Fermi National Accelerator Laboratory (FNAL) and the University of Chicago – recently conducted a study that indicated how a sufficiently advanced civilization might be able to harvest these stars and prevent them from expanding outward.
The Ramfjordmoen Facility of the European Incoherent Scatter Scientific Association (EISCAT) near Tromso, Norway. The facility contains several radio telescopes used to study interactions between the sun and the Earth's ionosphere and magnetosphere. At the left, the circular dish is the 32 meter diameter steerable dish that was used to transmit a message toward's Luyten's star or GJ273. This star is known to be circled by a potentially habitable extrasolar planet known as GJ273b.
The ‘Language in the Cosmos’ symposium
Three times in October, 2017 researchers turned a powerful radar telescope near Tromsø, Norway towards an invisibly faint star in the constellation Canis Minor (the small dog) and beamed a coded message into space in an attempt to signal an alien civilization. This new attempt to find other intelligent life in the universe was reported in a presentation at the ‘Language in the Cosmos’ symposium held on May 26 in Los Angeles, California.
METI International sponsored the symposium. This organization was founded to promote messaging to extraterrestrial intelligence (METI) as a new approach to in the search for extraterrestrial intelligence (SETI). It also supports other aspects of SETI research and astrobiology. The symposium was held as part of the International Space Development Conference sponsored by the National Space Society. It brought together linguists and other scientists for a daylong program of 11 presentations. Dr. Sheri Wells-Jensen, who is a linguist from Bowling Green State University in Ohio, was the organizer.
METI International
This is the second of a two part series about METI International’s symposium. It will focus on a presentation given at the symposium by the president of METI International, Dr. Douglas Vakoch. He spoke about a project that hasn’t previously gotten much attention: the first attempt to send a message to a nearby potentially habitable exoplanet, GJ273b. Vakoch led the team that constructed the tutorial portion of the message. Dr. Douglas Vakoch, president of METI International. (Credit: Per Bifrost public domain)
Message to the stars
The modern search for extraterrestrial intelligence began in 1960. This is when astronomer Frank Drake used a radio telescope in West Virginia to listen for signals from two nearby stars. Astronomers have sporadically mounted increasingly sophisticated searches, when funding has been available. The largest current project is Breakthrough Listen, funded by billionaire Yuri Milner. Searches have been made for laser as well as radio signals. Researchers have also looked for the megastructures that advanced aliens might create in space near their stars. METI International advocates an entirely new approach in which messages are transmitted to nearby stars in hopes of eliciting a reply.
The project to send a message to GJ273b was a collaboration between artists and scientists. It was initiated by the organizers of the Sónar Music, Creativity, and Technology Festival. The Sónar festival has been held every year since 1994 in Barcelona, Spain. The organizers wanted to commemorate the 25th anniversary of the festival. To implement the project, the festival organizers sought the help of the Catalonia Institute of Space Studies (IEEC), and METI International. The Sónar Music, Creativity, and Technology Festival of Barcelona, Spain was a sponsor of the message to GJ273b.
To transmit the message, the team turned to The European Incoherent Scatter Scientific Association (EISCAT) which operates a network of radio and radar telescopes in Finland, Norway, and Sweden. This network is primarily used to study interactions between the sun and Earth’s ionosphere and magnetic field from a vantage point north of the arctic circle. The message was transmitted from a 32 meter diameter steerable dish at EISCAT’s Ramfjordmoen facility near Tromso, Norway, with a peak power of 2 megawatts. It is the first interstellar message ever to be sent towards a known potentially habitable exoplanet.
The target system
The obscure star known by the catalogue designation GJ273 caught the attention of the Dutch-American astronomer Willem J. Luyten in 1935. Luyten was researching the motions of the star. The star caught his attention because it was moving through Earth’s sky at the surprising rate of 3.7 arc seconds per year. Later study showed that this fast apparent motion is due to the fact that GJ273 is one of the sun’s nearest neighbors, just 12.4 light years away. It is the 24th closest star to the sun. Because of Luyten’s discovery it is sometimes known as Luyten’s star.
Luyten’s star is a faint red dwarf star with only a quarter of the sun’s mass. It caught astronomers’ attention again in March 2017. That’s when an exoplanet, GJ273b, was discovered in it’s habitable zone. The habitable zone is the range of distances where a planet with an atmosphere similar to Earth’s would, theoretically, have a range of temperatures suitable to have liquid water on its surface. The planet is a super Earth, with a mass 2.89 times that of our homeworld. It orbits just 800,000 miles from its faint sun, which it circles every 18 Earth days. Artist’s impression of a habitable exoplanet orbiting a red dwarf star. The habitability of the planets of red dwarf stars is conjectural (Credit ESO/M. Kornmesser public domain)
This exoplanet was chosen because of its proximity to Earth, and because it is visible in the sky from the transmitter’s northerly location. Because GJ273b is relatively nearby, and radio messages travel at the speed of light, a reply from the aliens could come as early as the middle of this century.
The Message
Comparisons with Voyager
The GJ273b transmission is not the first time a message intended for extraterrestrials has been sent into space. Probably the most familiar interstellar message is the one carried on board the Voyager 1 and 2 spacecraft. NASA launched these interplanetary robots in 1977. They traveled on trajectories that hurtled them into interstellar space after they completed their missions to explore the outer solar system.
The message carried aboard each Voyager spacecraft was encoded digitally on a phonographic record. It was largely pictorial, and attempted to give a comprehensive overview of humans and Earth. It also included a selection of music from various Earthly cultures. These spacecraft will take tens of thousands of years to reach the stars. So, no reply can be expected on a timescale relevant to our society.
In some ways the GJ273b message is very different from the Voyager message. Unlike the Voyager record, it isn’t pictorial and doesn’t attempt to give a comprehensive overview of humans and Earth. This is perhaps because, unlike the Voyager message, it is intended to initiate a dialog on a timescale of decades. It resembles the Voyager message in that it contains music from Earth, namely, music from the artists that performed at the Sónar music festival.
The message consists of a string of binary digits—ones and zeros. These are represented in the signal by a shift between two slightly different radio frequencies. The ‘hello’ section is designed to catch the attention of alien listeners. It consists of a string of prime numbers (numbers divisible only by themselves and one). They are represented with binary digits like this:
01001100011100000111110000000000011111111111
The message continues the sequence up to 193. A signal like this almost certainly can’t be produced by natural processes, and can only be the designed handiwork of beings who know math.
The tutorial
After the ‘hello’ section comes the tutorial. This, and all the rest of the message, uses eight bit blocks of binary digits as the basis for its symbols. The tutorial begins by introducing number symbols by counting. It uses base two numbers like this:
The leading ‘1’ allows numbers to be distinguished from other 8 bit symbols that don’t represent numbers.
After counting, the tutorial introduces symbols for the operations of arithmetic by showing sample problems. Here’s a sampling of some of the symbols for math operations:
The tutorial then proceeds to geometry using combinations of numbers and symbols to illustrate the Pythagorean theorem. It eventually progresses to sine waves, thereby describing the radio wave carrying the signal itself. Finally the tutorial describes the physics of sound waves and the relationships between musical notes.
Besides the numbers, the tutorial introduces 55 8-bit symbols in all. It provides the instructions that aliens would need to properly reproduce a series of digitally encoded musical selections from the Sónar Festival.
During its journey of 70 trillion miles, the message is sure to become corrupted with noise. To compensate, the tutorial was transmitted three times during each transmission, requiring a total of 33 minutes to transmit. The entire transmission was repeated on three separate days, October 16, 17, and 18, 2017. A second block of three transmissions was made on May 14, 15, and 16, 2018.
The music
Each transmission included a different selection of music, with the works of 38 different musicians included in all. You can hear recordings of all this music at the Sónar Calling GJ273b website.
The rationale behind the message
Current and past SETI projects conducted by astronomers here on Earth assume that advanced aliens would make things easy for newly emerging civilizations by establishing powerful beacons that would broadcast in all directions at all times. Thus, SETI searchers generally use the same sort of highly directional dish antennae often used for other research in radio astronomy. They listen to any one star for only a few minutes, searching each one in turn for the beacon.
Unlike the always-on beacons imagined as the objects of Earth’ SETI searches, the Sónar message was only transmitted for 33 minutes on each of three days, and on only two occasions. Vakoch admits that “our message would likely be undetected by a civilization on GJ273b using the same strategy” favored by beacon searching SETI researchers on Earth.
However, some researchers have called traditional SETI assumptions and strategy into question, and studies of alternative search technologies have already been conducted. Vakoch notes that “we humans already have the technological capacity, and need only the funding, to conduct an all-sky survey that would detect intermittent transmission like ours”.
A larger problem is that the message was directed at just one planet. Although GJ273b orbits within its star’s habitable zone, we really know little what that means for whether the planet is actually habitable, or whether it has life or intelligence. Earth itself has been habitable for billions of years. But it has only had a civilization capable of radio transmissions for a century.
Vakoch conceded that “The only way we will get a reply back from GJ273b is if the galaxy is chock full of intelligent life, and it is out there just waiting for us to take the initiative. More realistically, we may need to replicate this process with hundreds, thousands, or even millions of stars before we reach one with an advanced civilization that can detect our signal”. METI International aims to conduct a design study for such a large scale METI project in hopes that funding will materialize from governmental or other sources.
