Antenne per esplorazioni interplanetarie

Signals from the deep space

A mysterious electromagnetic wave has reached our radio telescopes, scientists are trying to find answers to this enigma.

by Luca Longo
16 November 2020
6 min read
by Luca Longo
16 November 2020
6 min read

Five hundred million years ago, a mysterious radio signal was launched from a far-away galaxy, now known by the rather dull name SDSS J015800.28 + 654253.0. When this electromagnetic wave started, the first trilobites of the Cambrian Period had just begun to swim about in the Earth’s seas, and it would be another 200 million years before the first reptiles set foot on land. Since this galaxy with the unpronounceable name is 500 million light years away from Earth, the signal has only just arrived. It was picked up by the radio telescopes of the Canadian Hydrogen Intensity Mapping Experiment Fast Radio Burst Project (CHIME/FRB).

This battery of radio telescopes has a total surface area of 2000 m2 and is in the White Lake National Park in Canada. From these remote hills, sheltered from almost all manmade electromagnetic disturbance, radio telescopes scan the sky looking for signals coming from the cosmos on radio frequencies between 400 and 800 MHz. This one from the distant galaxy has been catalogued as an anomalous Fast Radio Burst (FRB). These types of powerful radio signals were discovered in 2007, but it is not yet clear what produces them. We only known that enormous energy sources are needed, the size of nuclear fusions occurring on stars much larger than our Sun.

An unusual signal

However, until now, all the FRBs discovered have sent out sudden and unpredictable signals. Some have sent a single signal, others more than one, but without any particular rhythm. That said, this most recent prehistoric signal from deep space is something of a surprise. It is as precise as a Swiss watch and repeats exactly over a period of just over two weeks. To be precise, after exactly 4 days of intense activity, the mysterious radio source turns off for just over 12 days, and then begins again with a regular rhythm. The entire cycle lasts exactly 16.35 days and was observed over 28 times from 16 September 2018 to 30 October 2019. This FRB, catalogued as FRB 180916.J0158 + 65, not only has unprecedented regularity, but is also the closest emission to Earth detected since the first FRBs were identified. Numerous research groups have attempted to answer questions about the energy bursts that might be producing these regular signals. We know where they are, but we don't know what they are yet.

The radio telescopes of the Canadian Hydrogen Intensity Mapping Experiment Fast Radio Burst Project

Waiting for an answer

Possible explanations can be put into two broad categories: models that suggest that the environment surrounding the FRB is responsible for the regular rhythm and models that assume that the source itself is being periodically switched on and off. One theory in the first category is that the FRB is orbiting a black hole. Because of this, it may only be able to emit signals towards us when it is in a certain stage of its orbit, when the black hole is unable to swallow the radio signal. But it could be a binary system, where a giant star and a second, very small but very dense star classified as a type of neutron star called a Pulsar, are revolving around each other.

In this case, the radio bursts emitted by the neutron star would be periodically eclipsed by the electromagnetic storms generated by its giant companion. The other category of theories begins with the idea that it is the source itself producing strong emissions at times and then as many pause periods. In fact, another particular class of neutron stars, called Magnetars, is made up of stars that rotate on their axis at very high speed and are able to emit strongly magnetised periodic radio signals. But in all the cases observed so far, Magnetars have periods of rotation that can only be measured for a few seconds, certainly not compatible with a complete cycle of over 16 days.

In the midst of this research by radio astronomy teams around the world, ufologists are also trying to get in on the act, claiming these signals are being sent by extraterrestrial civilisations. We can’t rule out the possibility that extraterrestrial civilisations exist and that they are trying to contact their neighbours by transmitting messages encoded in radio signals. Here on Earth we tried the same thing 45 years ago with the Arecibo radio telescope. But if this FRB were produced by an intelligent life form, we would have to conclude that, while animal life was just beginning on Earth, someone, 500 million light years away, already had the capability to use nuclear fusion from entire Suns to signal their presence. More surprisingly, in the following 500 million years, they didn’t have the inclination or time to come and visit us!

Stay tuned

Meanwhile, radio astronomers from all over the world are trying to make sense of this phenomenon and the CHIME/FRB team are analysing the mountain of data already collected over recent years. At the same time they are scanning surrounding space looking for other FRBs that have a similar frequency rhythm to this mysterious radio signal, which as of today is absolutely unique in the entire known Universe and at the same time our neighbourDoes anything change for us? Today, when we want to know what time it is we only have to look at our smartphones, smartwatches or any of the electronic devices we have at hand. The hours and minutes change with precision on our home screens, constantly synchronised thanks to our Internet connections.

Even when daylight saving time changes, we don't have to do anything now, but we all remember just a few years ago, having to check a reliable source from time to time. We turned to the TV time signal and the more sophisticated among us used our radio-controlled clock to pick up the DCF77 signal emitted by the Frankfurt radio station that reached the whole of Italy, except Sicily. But from today, if we really want to show off, we can use a radio telescope tuned to galaxy SDSS J015800.28 + 654253.0 to stay perfectly synchronised wherever we are in the Universe –including Sicily!