Mysterious signals from the nearest star – what are they?

BLC1 is not a signal from an intelligent extraterrestrial civilization, but rather a radio interference. Detailed research results are described in Nature Astronomy. This means that we have to wait a little longer for a message from the “aliens”.

The BLC1 signal was detected in April 2019, when Andrww Zic of the University of Sydney began observing the star Proxima Centauri. An object 4.22 light-years away is the closest star to us, though too faint to be seen with the naked eye. Zic observed a Proxima Centauri flare – similar to the one emitted by the Sun (along with coronal mass ejections). This is the trait of all stars.

There is a planet – Proxima Centauri b – orbiting around Proxima Centauri, which is constantly influenced by the cosmic weather. While this does not preclude the existence of life there, the surface of the planet is likely to be extremely inhospitable. Scientists have long wondered whether Proxima Centauri b may have conditions conducive to the emergence of life. Perhaps one day we will find out about it, because this system is one of the few that we can visit in our lifetime.

A spacecraft traveling at a speed close to the speed of light would need around 9 years for a round trip. It is still too far for our technological capabilities, but in the near future, nanostats using space sail technology may reach there. That is why it is important to understand this planetary system.

The detected BLC1 signal was intriguing, although scientists remained aloof for a long time. Sofia Sheikh from Penn State University was responsible for the BLC1 analysis. There are many indications that BLC1 may be a sign of an extraterrestrial technology – the so-called technosignature. Surprisingly, BLC1 was only detectable when we were looking towards Proxima Centauri (no so-called out-of-source observations) – this is unusual because most astronomical phenomena are visible from all directions. Moreover, the signal only occupies one narrow frequency band, while emissions from stars or other astronomical objects typically occur over a wider range.

The analysis of Sofia Sheikh’s team showed that the BLC1 most likely has an earthly origin. It’s probably a radio interference from our planet. Scientists found similar signals after scanning the entire frequency range of the Parkes Observatory.

We do not know exactly what the source of BLC1 is, or why the signal was not detected in the off-source observations. Some suggest that BLC1 is a so-called intermodulation, which is the phenomenon where two frequencies mix together to create a new signal. This can be seen, for example, during “distortion” while playing the guitar. BLC1 is probably just such a signal. However, this does not mean that we should stop observing the sky, because Proxima Centauri is only one of hundreds of billions of stars in the Milky Way.