Get A Radio Signal From Space: The Most Mysterious Messages From The Universe To Mankind

We know that sound does not propagate in space. Sound is a wave, mechanical vibrations of particles of a material medium, and space is an almost perfect vacuum, devoid of matter to transmit these waves. But this does not mean that space is silent. In fact, it constantly “buzzes” in the radio range as if trying to tell us something.

Each radio signal from space, like a message in a bottle fished out from the endless ocean of stars, makes us think about our place in the Universe and the possibility of other civilisations’ existence. We insistently try deciphering the language used, but many remain a mystery. This article will tell you about such mysterious radio signals from space. But first, a bit of background.

What Was The First Radio Signal From Space?

The first space radio signal was discovered in 1932 by American radio engineer Karl Jansky. He worked at Bell Telephone Laboratories and was researching sources of radio interference that could affect transatlantic radio-telephone communications. At that time, radio communications were the newest technology, and interference was a serious problem.

For his research, Jansky constructed a large antenna nicknamed the “Jansky’s Merry-go-Round.” It consisted of a wooden frame with an array of dipole antennas mounted on four wheels from an old Ford Model T. The entire structure rotated, making one revolution every 20 minutes, which allowed it to scan the sky in different directions.

One day, while observing at 20.5 MHz, Jansky captured a faint but persistent hissing noise he could not explain. The noise was unlike any other interference he had ever heard. It exhibited a strange periodicity – its intensity varied throughout the day, peaking every 23 hours 56 minutes.

Jansky excluded all possible terrestrial noise sources and concluded that the unexplained radio signal comes from space — and not from the Sun but from the direction of the Sagittarius constellation, where the centre of our Milky Way galaxy is located. Thus, Karl Jansky became the discoverer of cosmic radio emission and the founder of radio astronomy — a section of astronomy that allows us to listen to space in radio range.

How Do We Listen To Space?

A radio telescope is the radio astronomer’s primary tool. The most powerful devices can capture signals of frequency from a few megahertz to hundreds of gigahertzes, amplifying and converting them for further analysis.

Signals can come from any astronomical object, i.e., pulsars, galaxies, stars, planets, etc. The choice of frequency depends on what exactly we want to study:

• Low frequencies: suitable for observing cold gas clouds and pulsars.
• High frequencies: allow studying hot objects such as quasars and active galactic nuclei.
• Frequency 1420 MHz (hydrogen line): a special frequency because that’s where hydrogen atoms, the most common element in the Universe, “sound.” Thanks to signals at this frequency, scientists can study the distribution of hydrogen in galaxies and intergalactic space. 

Why Is 1420 MHz Forbidden?

The thing is, any terrestrial transmissions at 1420 Mhz can interfere and “jam” a weak space radio signal. Imagine trying to hear a whisper on a noisy street — it will be next to impossible. That’s why the International Telecommunication Union (ITU) banned the use of 1420 MHz for terrestrial transmitters not to “interfere” with astronomers “listening” to space.

What Are The Radio Sounds Coming From Space?

The Universe is a real orchestra of radio sounds. Depending on the object they emanate from, they can sound like crackling, humming, chirping, whistling, splashing, and even whispering, which is what we habitually call relic radiation background. Usually, all these sounds are of natural origin. However, scientists sometimes record signals that raise doubts about their natural character. Such signals are distinguished by their unusual structure, intensity, or periodicity and are called “techno signatures”. What does this mean?

Imagine that we are looking for traces of aliens. Biosignatures are like footprints in the sand; they indicate the presence of some kind of life. Technosignatures are signals that may indicate the existence of technologically advanced extraterrestrial civilisations or astrophysical phenomena unknown to us; for example, these could be impulses from some structures or space stations, artificial radio bursts, changes in the atmospheric composition of exoplanets, etc.

Not all unusual space signals are techno signatures. That’s why scientists carefully analyse each signal, eliminating all possible interference and alternative explanations. Let’s find out how successful they are in this regard.

1. “Little Green Men” (1967)

In 1967, at the height of the Cold War, a young Cambridge University PhD student named Jocelyn Bell discovered unusual pulsating signals while studying the flickering of quasars using a new radio telescope. They were so regular (with a period of 1.33 seconds) that Bell and her supervisor, Antony Hewish, initially suggested that they might be signals from an extraterrestrial civilisation. The source of the signal was even given the name LGM-1 (Little Green Men).

However, it soon turned out that these signals had been coming from previously unknown objects – rapidly rotating neutron stars called pulsars. This discovery was a major milestone in the development of astronomy and astrophysics, and Antony Hewish was awarded the Nobel Prize in Physics in 1974. Unfortunately, Jocelyn Bell’s contribution to this discovery was not appreciated, but this did not stop her from becoming one of the most outstanding astrophysicists in the world.

2. WOW And The Silence (1977)

What was the radio signal from space in 1977? On August 15, 1977, the Big Ear radio telescope at Ohio State University Observatory, working as part of the SETI (Search for Extraterrestrial Intelligence) project, recorded an unusual signal that went down in history as the “Wow!” signal. This short but very powerful signal from deep space lasted 72 seconds and came from the constellation Sagittarius. Its characteristics — a narrow frequency band and significant amplification compared to background noise — corresponded to the expected signal from an extraterrestrial civilisation. Astronomer Jerry Ehman, who found this signal on a data printout, was so amazed that he circled it with a red pen and wrote, “Wow!” However, despite all subsequent attempts, the “Wow!” signal never repeated itself, and its source was never identified.

In 2024, researchers from the Arecibo WOW project tried to find similar space signals. To do this, they analysed data from the Arecibo telescope for 2017-2020 and discovered less bright Wow! mimicry signals, which were the result of activity in interstellar clouds of cold hydrogen (HI). Based on their discovery, the scientists suggested that the origin of the wow signal could be a magnetar — a type of neutron star with a very strong magnetic field that could excite hydrogen atoms in the clouds.

3. Jupiter Singing (1996)

In 1996, the Galileo spacecraft approached Jupiter and detected unusual signals coming from the giant planet. These signals, called “electromagnetic choirs,” sounded like the whistling and chirping of birds. Astronomers believe they are caused by the interaction of Jupiter’s powerful magnetic field with charged particles.

Galileo also detected decametre radio bursts associated with volcanic activity on Jupiter’s moon Io. These observations helped scientists better understand processes occurring in Jupiter’s magnetosphere and the planet’s interactions with its satellites.

4. SHGb02+14a — Message In “Hydrogen Language” (2003)

As part of the SETI@home project, aimed at searching for extraterrestrial intelligence using distributed computing on volunteer computers, a weak signal called SHGb02+14a was recorded three times in 2003. The signal came from the area between the constellations Pisces and Aries, which has no visible stars or planets. SHGb02+14a was detected at that same frequency forbidden on Earth, 1420 MHz, which corresponds to the emission line of neutral hydrogen, the most common element in the Universe. This led scientists to the idea that an extraterrestrial civilisation may use this “universal” frequency to attempt communication. Unfortunately, SHGb02+14a has not been repeated, and scientists have not been able to obtain additional information about its nature; still, many consider it a “greeting” from aliens and are waiting for a recurrence.

5. Cosmic Roar (2006)

In 2006, astronomers conducted the ARCADE (Absolute Radiometer for Cosmology, Astrophysics, and Diffuse Emission) experiment to study the cosmic microwave background radiation. To do this, they launched a high-altitude balloon with a radiometer to an altitude of 37 km above Texas.

Instead of the expected uniform signal of the relic radiation, scientists found unexplained radio noise, the intensity of which was six times greater than theoretical predictions. This noise was called the “cosmic hum.”

The “cosmic hum” remains an unexplained radio signal from space. One hypothesis states that it is an echo of the first stars and galaxies formed in the Universe. However, this hypothesis cannot fully explain the high intensity of the noise. Another hypothesis links the “cosmic hum” to radio emission from hot gas in galactic halos, and some scientists associate its origin with the annihilation of dark matter particles.

6. Lorimer Burst (2007)

In 2007, astronomer Duncan Lorimer, while analysing archived data from the Parkes radio telescope in Australia, discovered an unusual, short-lived emission burst emanating from a point located at 3° from the Small Magellanic Cloud, about one gigaparsec (about 3 billion light-years) away. The burst, which lasted only a few milliseconds, was so powerful that its energy was comparable to the energy released by the Sun over several days.

The discovery was initially met with disbelief, but soon, other telescopes started to detect similar bursts, which were officially named fast radio bursts (FRBs).

The origin of FRBs remains a mystery. Possible sources include magnetars (neutron stars with extremely strong magnetic fields), black holes, colliding neutron stars, and even extraterrestrial civilisations using powerful transmitters for interstellar communication. Some FRBs repeat periodically, making their identification even more difficult.

7. An Unknown Radio Source In The Cigar Galaxy (2010)

In April 2010, while observing the Messier galaxy M82 (also known as the “Cigar” due to its elongated elliptical shape), astronomers from the Jodrell Bank Observatory at the University of Manchester detected an unusual radio source.

M82, located 10 million light years from Earth, is known for its vigorous activity: it undergoes intense star formation, with stars being born 10 times faster than in our Milky Way galaxy. However, the space signal detected by the observatory’s main instrument, the Lovell radio telescope, was unlike any known astronomical phenomenon. It had unique characteristics that did not correspond to the radiation of pulsars, quasars, or other known space objects. Scientists have put forward several hypotheses about its origin, including a microquasar with unusual properties or a relativistic outburst from a massive black hole. However, none of the versions has been definitively confirmed. The signal from galaxy M82 remains one of the biggest mysteries of radio astronomy.

8. Big Hello From HD 164595 (2015)

In 2015, the Russian RATAN-600 radio telescope in Karachay-Cherkessia detected a powerful signal coming from the star HD 164595, located 95 light years from Earth in the constellation Hercules. This star is similar to our Sun and has at least one known exoplanet, a gas giant similar to Neptune. The signal lasted only 2 seconds but was so strong that if it had been emitted isotropically (evenly in all directions), its generation would have required energy comparable to the energy consumption of our entire planet. In other words, the signal was powerful enough to be considered a potential sign of technological activity.

This has generated a lot of interest from extraterrestrial intelligence researchers. However, the signal did not repeat itself, and after detailed analysis, scientists came to the conclusion that it was most likely caused by some yet unknown astronomical phenomenon, such as gravitational lensing, a star flare, or, even more prosaically, interference or reflections from satellites.

9. A Mysterious Metronome From The “Сarpenter’s Square” (2018)

In 2018, Curtin University student Natasha Hurley-Walker, while analysing data from the Murchison Widefield Array (MWA) radio telescope in Australia, recorded an unusual, repeated radio signal from space every 18 minutes. This signal, designated GLEAM-X J162759.5-523504.3, came from the direction of the constellation Norma (or Carpenter’s square) and had several strange features.

First, its period was incredibly long and precise for all known pulsating objects in space — exactly 18 minutes 18 seconds, which is why it was nicknamed the metronome. Second, each pulse lasted from 30 to 60 seconds, which is also unusually long. Third, the brightness of the signal varied greatly from flash to flash.

Scientists have put forward several hypotheses about the nature of this repeating radio signal, but so far, none of them can fully explain all of its features. Perhaps it is an ultra-long period magnetar — a neutron star with a strong magnetic field and very slow rotation. Or it is a white dwarf with unusual properties. Or maybe we have encountered something entirely new that will turn our understanding of the Universe upside down?

The mystery of GLEAM-X J162759.5-523504.3 remains unsolved. The signal was observed for three months in 2018 and then disappeared, leaving even more questions behind. Scientists continue to study the data, hoping to find answers and solve the mystery of this cosmic metronome.

10. A Message 8 Billion Years Old (2022)

In June 2022, the Australian Square Kilometre Array Pathfinder (ASKAP) radio telescope detected a short and incredibly powerful pulse of radio waves, dubbed FRB 20220610A. This FRB was four times more energetic than other fast radio bursts, but that’s not all the features making it unique. 

In October 2023, researchers from the European Southern Observatory (ESO) using the Very Large Telescope (VLT) in Chile found that FRB 20220610A comes from a distant galaxy located 8 billion light-years from Earth. To measure the age of the signal, the dispersion method was used — the delay of the signal at different frequencies due to passage through the interstellar medium, which contains free electrons. In simple terms, this method measures the amount of matter through which the signal has passed, and the more matter there is, the greater the distance the signal has travelled.

Thus, the detection of the 8 billion-year-old radio signal gives us a unique opportunity to look back in time to a period when the Universe was only 5.8 billion years old and, thus, better understand its evolution. Let’s agree, this is an incredible discovery.

What Is The Universe Trying To Tell Us?

Every mysterious radio signal from space is a reminder of how much we still don’t know about the Universe. These messages in bottles fished out from the ocean of stars fuel our curiosity and inspire new research. Perhaps one day, we will be able to unravel their secrets and receive long-awaited proof of the extraterrestrial civilisations’ existence. In the meantime, all we can do is watch, listen, and continue searching because deep space is full of wonders just waiting to be discovered.

References And Additional Information:

• Radio source https://www.britannica.com/science/radio-source
• The Science of Radio Astronomy https://public.nrao.edu/radio-astronomy/the-science-of-radio-astronomy/
• WOW https://phl.upr.edu/wow/summary
• What is the Hydrogen Line? http://www.setileague.org/askdr/hydrogen.html
• Technosignatures https://www.newscientist.com/definition/technosignatures/
• The SETI Episode in the 1967 Discovery of Pulsars https://www.researchgate.net/publication/235358985_The_SETI_Episode_in_the_1967_Discovery_of_Pulsars
• Mystery object in Starburst Galaxy M82 possible micro-quasar https://www.sciencedaily.com/releases/2010/04/100413202858.htm
• Radio Frequency Signals in Jupiter’s Atmosphere  https://www.jstor.org/stable/2890211
• Fast Radio Bursts https://astronomy.swin.edu.au/research/utmost/?page_id=103
• Unknown space object beaming out radio signals every 18 minutes remains a mystery https://edition.cnn.com/2022/01/26/world/unusual-space-object-transient-scn/index.html
• A mysterious radio signal from 8 billion years ago has just reached Earth https://www.indy100.com/science-tech/radio-signal-reaches-earth-2669260161