Sónar, Barcelona's music, creativity and technology festival celebrates its 25th anniversary. Since its inception in 1994, Sónar has remained true to its name and has continued to track the most innovative, radical and engaging music on the planet. To celebrate its 25th year, Sónar has decided to reverse its role, switching from radar to antenna. This is how the Sonar Calling project GJ273b was born in which a quarter of a century of musical exploration will be condensed and sent it into space, specifically to the exoplanet Luyten Star b, with the objective of making first human contact with an extra-terrestrial intelligence.

Sónar leads this artistic-scientific experiment in collaboration with two pioneering institutions in the detection of extra-terrestrial life: the IEEC (Catalonia Institute of Space Studies) and METI International (Messaging Extra-terrestrial Intelligence). The project involves 35 artists linked to the festival, from diverse musical origins and discourses. The IEEC is a research institute that studies all areas of space science, including the planet Earth, the Solar System, exoplanets, stellar physics, astroparticle physics, and cosmology. The IEEC conducts projects on the discovery of habitable planets and has supported the search for extra-terrestrial intelligence (SETI, SETI@home and BOINC) for more than a decade and hosts the website SETI.cat. The project’s second partner is METI International, the ground breaking organization in the design of messages capable of being understood by extra-terrestrial civilizations. Founded in 2017, it carries out scientific research and educational programs on the sending of Intelligent Extra-terrestrial Messages (METI) and the Search for Extra-terrestrial Intelligence (SETI).

Contact with an extra-terrestrial intelligence has been an object of interest and fascination for decades. In the 70's, the first SETI named projects (search for extra-terrestrial intelligence) were carried out, which included the use of the Arecibo radio telescope (Puerto Rico) both to detect possible emissions of civilizations in other star systems and for the sending of radio messages, and materials in space probes, to interplanetary space. Much energy has been focused on listening to different stars to detect signs of alien intelligence. Thus far there have been no positive results, apart from a single signal, the so-called “Wow!”, which has yet to be explained. Since 1974, transmissions have been sent to well known brightly shining stars, as well as to stars with giant exoplanets. There has been no success to date. In recent years many exoplanets have been discovered orbiting stars similar to the Sun, with some of them seeming to meet the requirements for habitable worlds. It is therefore the perfect time to make a first attempt at communication with these planet’s hypothetical civilizations.

For the second transmission in May 2018 the project counts with the collaboration of the Canadian astrophysicist Dr. Yvan Dutil who back in 1999 together with his colleague Stéphane Dumas defined a small “dictionary” of symbols or concepts, each described with an image of a few pixels. The tutorial section of our message presents the different concepts little by little, as if we were teaching a baby to talk.

From a scientific point of view, this experiment is unique as it directs a transmission to a specific nearby exoplanet that appears to offer the necessary conditions to house life. The encoding, cadence and power used to send the message is also unique and significantly increases the chances of it being received and understood by a non-terrestrial intelligence. The design of the message by IEEC and METI is propaedeutic: each section of the message contains the necessary information to decode the next section. The message contains both basic information about humanity and several pieces of music. From a musical standpoint, this project is innovative due to the active participation of a significant number of musicians of renown who have created special musical pieces to be sent to Luyten's Star b.

The transmission is directed at the Luyten Star, also known as GJ 273. Luyten's Star is located in the Canis Minor constellation at a distance of 12.4 light years from Earth. It is a much cooler star than our Sun with a temperature of around 3,000ºC (compared to the Sun’s 5,500ºC) and is therefore more reddish in colour. We estimate a mass and a radius that is approximately one third of our sun’s. The star is not visible without a telescope. It was named after a Dutch-American astronomer, Willem Jacob Luyten, who measured its movement (compared to other distant stars). In 2017 he announced the discovery of two orbiting planets. One of them, with a mass almost three times greater than the Earth, is located in the innermost edge of the habitable zone of the star. Its year is equivalent to 19 days on our own planet. It is called the Luyten Star b. This planet also has a nearby smaller neighbour with a mass 30% more than that of our own planet and whose year lasts around 5 days, it is called Luyten’s Star c. We do not know if Luyten’s Star b has water, nor if retains an atmosphere that makes it habitable. But presently we also have no reason to think otherwise. If it did, it would be a world with oceans like ours, perhaps hotter, with a sky lit by a star larger in appearance than the sun, shining with a reddish glow.

This is not the first time that a message has been sent into space. On November 16, 1974, a message known as the Arecibo Message was sent from the Arecibo radio telescope in Puerto Rico in the direction of the M13 cluster of stars (Globular Cluster). It is estimated that this transmission will reach its destination in around 27,000 years. Messages have also been sent to 25 other stars, including the bright Polar and Altair stars which are unlikely to have habitable planets, and other stars where giant planets have been discovered (lifeless as far as we know). These are the projects carried out to date: https://en.wikipedia.org/wiki/Active_SETI

Unlike the majority of previous communications, this message has been designed with scientific and technical rigor. It has a specific destination, the exoplanet around Luyten's Star (or GJ 273), which is a nearby planet (12.4 light-years away) with the potential to support life and a distance that allows us to calculate the estimated time of arrival and when we could expect to receive an answer. Also the content in previous messages meant that the necessary information to decipher them depended excessively on a specific form of human knowledge (for example, the convention of graphic representations in two dimensions, or the codification of text characters and of course human languages). This message is unique in that to be understood it will not require the need for terrestrial convention. Likewise, the cadence for the transmission of information is sufficiently slow (for the antenna and power used) to allow its correct decoding at that distance, using antennas and receivers similar to our own. As for the music, it is the first time that a set of musical pieces has been created specifically to be transmitted into space, preceded by sufficient 'explanations' to decode and listen to them.

The Luyten's Star planet was chosen after assessing all available options. It is a relatively nearby and potentially habitable exoplanet, so the message should arrive in just over 12 years. In addition, Luyten's Star is observable from the high terrestrial latitude occupied by the EISCAT antenna in Tromsø, which allows the transmission to be made from this location.

No, there have been other radio-frequency music transmissions directed towards space. In 2001 the 'Teen Age Message' was sent, with various musical pieces using the 'Theremin' instrument, to several relatively nearby stars (45 to 70 light years away), one of which appears to have 3 planets similar to Jupiter orbiting around it. In 2008 the Beatles song 'Across the Universe' was sent to the Polar star. Meanwhile in 1977 the aptly titled Voyager Mission included a 90-minute recording in the form of a physical disc, known as the Golden Disc, representing music from Earth and a message of goodwill from Humanity.

Our interstellar message is a radio wave emission, similar to a radio broadcast on Earth, only at a different frequency and with a much higher power output. A radio signal (like any radio program) is linear: information bits and sound follow one another over time. Therefore, this medium is particularly suitable for transmitting information that is also linear, such as music or text. Of course, images can also be transmitted by radio waves, and was done, for example, in the Arecibo message in 1974, but this requires a degree of complication in the encoding of the message, which reduces the chances of being deciphered by a hypothetical extra-terrestrial intelligence. Choosing between the two forms of linear communication, music and text, was easy: music, or more generally speaking, an audio signal, offers the possibility of transmitting spoken word (an option which a significant number of artists contributing to the project have opted for), while the reverse option is impossible, unless some form of written musical coding is included, something that would again increase the artificiality of the transmission and reduce the chances of being understood by a non-human intelligence.

Sónar festival has selected 35 musicians or groups, with the criteria that they provide a complete and varied representation of Sónar’s 25-year lifecycle, and what it may become in the future. The criterion is in no way stylistic. The questions we have asked are: Who are the creators who have opened new musical pathways in recent years? Who do we think will do so in the years to come? This selection will be completed with 3 musicians or groups’ chosen in an 'open call' to the general public. We want to take this special opportunity to discover new talents. Furthermore, it would be inconceivable for Sónar not to involve its public in such a project.

In order to optimize the transmission via radio antenna, and considering the very slow data rate (only 500 bits per second, about 250 thousand times slower than a typical MP3), the musicians have composed pieces lasting just 10 seconds and of very low digital sound quality. Specifically, a PCM encoding of only 8 bits, monaural, where a sample rate of only 8 kilohertz has been used. As a reference, a Compact Disc uses 16-bit PCM coding, stereo and 44.1 kilohertz. This means that the transmitted pieces cannot contain high pitches (due to the low kilohertz sampling) and that, moreover, they will be heard with some digital noise (8 bits). It is worth noting that no type of audio compression (such as MP3) is used, but the music is transmitted in the most basic digital format. Not only that, but the musical pieces are preceded by a brief 'tutorial' that easily describes the digital coding of sound waves, using different frequencies and harmonics. This should allow an intelligent extra-terrestrial species to 'understand' and 'listen' to this music.

The message has been organized in several parts. Firstly a greeting is transmitted at the minimum cadence, and is purposely designed to attract the attention of any extra-terrestrials, indicating that it is not a natural radio signal created by an object or astronomical phenomenon. Next, some basic human information is transmitted: numbers, mathematical equations, physical concepts, etc. Subsequently a short musical tutorial is transmitted describing our method for digitally encoding sounds, which will allow for the ability to decipher and understand the last part of the message: music. The message concludes with a brief farewell, consisting of the initial greeting transmitted in reverse.

An exoplanet or extrasolar planet is a planet that orbits a different star to the Sun and therefore does not belong to the Solar System.

The first confirmation of an exoplanet occurred in the 1990s. Although today we know that an object announced in 1992 is probably an exoplanet, the discovery of 51 Peg b in 1995 by Michel Mayor and Didier Queloz is considered to be the start of the investigation into exoplanets. As of October 2017, 3,671 planets and 2,751 planetary systems have been detected, of which 616 contain more than one planet. The main techniques for discovering exoplanets are indirect, that is, they are not based on observing the planet directly but on the effects that it exerts on its star, whether by changing its speed, position or brightness. Thus, the most successful methods are radial velocities (or the Doppler effect) and transits. The first allows us to discover planets and measure their mass from the oscillating movements that a star undergoes because of a (invisible) planet that orbits it. The second allows us to discover planets and measure their radius if the orbital plane of the planet coincides with our line of sight, which therefore enables us to observe eclipses during which the planet covers part of the star thereby decreasing its brightness.

The transmissions will take 12.4 light years to reach Luyten's star b. If intelligent life indeed exists and wanted to contact Earth, we could expect an answer within 25 years. As a scientific experiment, the hope would be to receive a response from Luyten's star b, which would unimaginably be the first Human contact with an extra-terrestrial civilization. As a musical experiment, the project is considered successful from the moment the first transmission is made. Irrespective of receiving an answer, the success of the project lies in the examination of the collective conscience concerning the feeling of belonging to humanity; why transmit, why transmit music and what music should we transmit?

The messages sent from Tromso in October 2017 and May 2018 will arrive at their destination after traveling through space for 12 years and 145 days, that is to say, in the year 2030. We do not know the precise distance to Luyten's Star, therefore the arrival time will occur around this date plus / minus one month.

The transmissions are made from the EISCAT facilities in Tromsø, Norway, using a 32-meter diameter antenna with a transmission power of 1.5 megawatts. As a reference, the largest NASA antennas measure around 70 meters and use approximately 0.4 megawatts. In the case of Sónar’s message we have used a 'radar' type antenna that emits pulses at a certain radiofrequency (around 930 megahertz) separated by silences. We have designed the transmission so that only 1 bit ('zero' or 'one') is sent in each of these pulses (using one frequency for 'zero' and another for 'one'). With this method, the message clearly indicates an intrinsic binary nature and a clear separation between consecutive bits. In addition, the transmission speed is very slow (from 62.5 to 500 bits per second), to maximize the chances of correct message decoding upon reception.

SETI, the extra-terrestrial intelligence search project, has for decades been looking for evidence that we are not alone in the Universe. Due to the incredible distances between stars, it is not feasible (at least for now) to directly observe another planet, let alone to see if it is inhabited. Therefore, indirect techniques are used to detect evidence of extra-terrestrial life, and not only life, but intelligent life. The technique most commonly used by SETI is based on 'listening' for possible radio frequency signals emitted by ETs. The problem lies in discerning natural signals (for example those emitted by objects and astronomical phenomena, such as pulsar stars, supernovae (or even normal stars) from artificial signals created by ET intelligence. Furthermore radio signals suffer great attenuation over the enormous interstellar distances. For this reason, SETI needs large antennas (such as the Arecibo radio telescope), complex mathematical algorithms, as well as a lot of data and huge computational power to try to single out a signal from all the cosmic noise. One of the most successful initiatives is the SETI@home project, whereby anyone in any country can help in this search by simply installing a program on their personal computer. Apart from the search for radio signals, SETI is also looking for optical signals, based on the assumption that extra-terrestrial intelligence is using powerful lasers to communicate between planets and stars.

A light year is not a unit of time but of distance. It is equivalent to approximately 10 trillion km (9,460,730,472,581 km) and is calculated by the distance that light travels in one year. The light year is the unit of distance used to talk about the stars in the solar environment. The closest to us, Proxima Centauri, is 4.2 light-years away, and the brightest star in the sky, Sirius, is 8.6 light-years away. Our galaxy, the Milky Way, has a diameter of about 150 thousand light years and the nearby Andromeda galaxy, one of the closest, is approximately 2.5 million light years from us.

We do not know. Science is attempting to answer this question and technology is advancing fast enough so that perhaps we will soon be able to gather enough evidence to provide an answer. What we have only recently learnt is that planets around other stars are extremely abundant and many of them are rocky (like ours) and located in the habitable zone of their stars. Estimates indicate that a minimum of one in four or five stars may have suitable planets that could sustain life. Moreover, when observing our own planet, we realize that life adapts to very extreme conditions. There are organisms, called extremophiles, that can withstand high pressures, highly acidic environments, high temperatures and extreme nuclear radiation conditions, and that can adapt to survive and multiply under these circumstances. Thus, if habitable environments are abundant and life adapts to extreme conditions, this leads us to speculate that life may be common in the universe. But we cannot say this definitively yet. The crucial question is: in a place where suitable conditions exist, what is the likelihood that life would emerge from nothing? Maybe it happens in 100% of cases, maybe one in a trillion, where the consequences would be totally different. Scientific research will hopefully provide us with an answer.

Human beings are curious by nature, and this curiosity has led us to the current levels of scientific, technological and social progress. We should not stop here. It would contradict our very way of being. The desire to understand and explore should extend to that which surrounds us on the largest possible scale. What is the context of the human being’s place in the universe? Are there other intelligent civilizations? To establish communication, someone has to take the first step and transmit. Maybe we are dealing with the zoo hypothesis.

We might think “revealing” our presence through radio transmissions involves the risk of a hypothetical “hostile” reaction on the part of another civilization. We do not know the nature of possible reactions, but this should not be a reason to avoid making ourselves known. Why dismiss a positive reaction? It is possible that a civilization in our Galaxy that has the technology to travel to our planet in fact detected us a long time ago. Our radio and television transmissions and airport radars have been emitting radiation/radio waves into space for 100 years now, meaning these transmissions have already travelled 100 light-years.

We know nothing about the conditions on the potentially habitable exoplanets that we have discovered so far. Perhaps these worlds are in fact inadequate for the presence of life. And even if there were life, we do not know if it would be complex and intelligent. Life appeared on Earth around 3.8 billion years ago. But this was in the form of bacteria until about 500 million years ago, when animals and complex plants appeared. Humans have been around for just 10,000 years and have had the ability to develop more or less sophisticated “technology”. So, if we use the evolution of life on Earth as a reference, it is highly likely that simple organisms incapable of communication may inhabit these planets.

The most commonly used technique is radio astronomy, which consists of focusing large parabolic antennas on the coordinates of the objects we wish to 'hear' (as if it were an artificial satellite from which we wanted to obtain a television signal). Strictly speaking, you are not able to 'listen' to the universe, since sound, as we know it, requires atmospheric pressure to propagate (and the space between planets and stars is empty). However, radio waves received with satellite dishes can be 'translated' into sound signals. When carried out correctly, it is possible to hear quite extraordinary sounds. Here are some examples: http://canyouactually.com/nasa-actually-recorded-sound-in-space-and-its-absolutely-chilling/ and https://www.pcmag.com/feature/353576/10-creepy-sounds-recorded-in-space-by-nasa/3

If the message does receive a response, it will be news of historical proportions. Humanity would also enjoy the unique opportunity to think of itself as a single species, to act with a truly global mentality and to respond in a way that represents everyone on the planet. It would provide the opportunity for a full-fledged revolution, the realization that we are not alone in the universe. This could in fact turn out to be the greatest political challenge to be addressed by the United Nations.

No, not all the artists who have contributed to this project will perform at Sónar 2018. A complete and representative sample of Sónar's 25-year history cannot be limited to one festival edition’s line-up. However all the selected artists have performed at Sónar at least once (some more than once!) or may do so in the near future.

The musical pieces from the 36 musicians or groups that have contributed to the transmission can be heard here. They will also be able to be heard during Sónar 2018 in a purpose built space.

No, we do not foresee sending further messages in the years to come.

This project will last a minimum of 25 years. Our message will take 12 and a half years to reach GJ 273b, traveling at Light Speed (which is the maximum speed at which information can travel in the Universe, according to Einstein's Theory of Relativity), and a hypothetical response would take the same time to return to Earth. It will therefore be possible to detect any responses from GJ 273b 25 years after the first transmission. However it could be extended, in the hope that, for example, the first message is received and answered, thereby opening an exchange with as yet unknown beings.