A scientific programme recently discovered radio bursts from a source in a galaxy about three billion light years away from Earth. What does that mean for us?
The search for extraterrestrial life (ET) has fascinated man for centuries, certainly since Copernicus established that the Earth was not the centre of the universe. But the hunt moved beyond conjecture and theorizing only in the 20th century, as we came to understand the universe better, and even travelled out into space. One recent initiative is the Breakthrough Listen project, launched two years ago by Russian tech investor Yuri Milner and cosmologist Stephen Hawking, which plans to survey one million stars, the galactic plane and 100 neighbouring galaxies in the search for intelligent life.
On 26 August, the Breakthrough Listen team detected 15 FRBs, or fast radio bursts, that originated from the location FRB 121102, named thus because it was discovered on 2 November 2012. According to a news release on the Breakthrough Listen website, FRBs are “brief, bright pulses of radio emission from distant galaxies". University of California, Berkeley postdoctoral researcher Vishal Gajjar, originally from Gujarat, who is with both the Berkeley SETI (Search for Extraterrestial Intelligence) Research Center and the Listen team, discovered this activity with the help of a backend instrument—a set of parallel processing computers that analyse signals collected from the telescope—at the Green Bank Telescope in West Virginia.
Gajjar and the Breakthrough Listen team search for broadband-like signals, which could indicate extraterrestrial civilizations. In an email interview, Gajjar explains how these detections are different from previous anomalies. Edited excerpts:
How brief were these radio bursts? How far is the source of these radio bursts from Earth?
The bursts we detected were only a few milliseconds wide. This allows us to constrain the size of the emission region to a width of only a few hundred kilometres. The distance between us and the source is truly enormous. Light travels at roughly 300,000 kilometres per second, yet it would take three billion years for any electromagnetic signals to reach us from this source. The signal we just received originated from the source around three billion years ago—a time when Earth did not have any complex life. If you think about it, it’s truly a remarkable thing that we are able to constrain the size of an astrophysical object to only a few hundred kilometres.
How powerful is the backend instrument at the Green Bank Telescope? What sort of data bandwidth were you dealing with?
The instrument we have used is one of a kind, a marvel of technology. It would be among some of the best backends available at any radio telescope. It is capable of simultaneously recording 6-GHz of bandwidth at a very high time resolution. We roughly record around 100 TB of data every hour of observation.
For our current observations, we have only used 4 GHz of the total bandwidth because the telescope only allows the signals from 4-8 GHz of radio frequencies at this particular frequency band.
How is this bunch of radio bursts different from some previous ones?
We have yet to understand so many things about this source and currently, many detailed investigations are underway, including ours. Our detections are unique compared to previous observations because this source has never been observed at such a high frequency, with such a wide bandwidth. In addition, we have noticed that the bursts we have detected with our backend show different frequency structures for individual bursts. In other words, the signal jumps around across the 4 GHz of our recorded bandwidth. This was only possible to investigate with the data collected by a backend like ours.
News releases mentioned that these radio bursts could be “directed energy sources used by extraterrestrial civilizations to power spacecraft"...
There are a number of theories being proposed to explain the origin of these FRBs, from black holes to neutron stars. A professor at Harvard University recently proposed that if extraterrestrials are accelerating their interstellar spacecraft using a microwave beacon, it might appear as the FRBs we are seeing here. But I think this particular signal we received is less likely to originate in an intelligent civilization, because we see these types of sources all over the sky. When pulsars were first discovered, they were also thought to come from ETs. But soon people started finding pulsars across the sky, and now the ET hypothesis is not favoured.
A similar argument can be raised regarding the ET spacecraft. Unless a good fraction of ETs use a similar technique—which is a long stretch—it’s unlikely that all FRBs have an artificial origin. Having said that, I think if ET would like to communicate with us, mimicking an FRB type signal and modulating it with an artificial message, it would not be difficult for us to find them, using similar techniques to those we have used here.
I think if ET would like to communicate with us, mimicking an FRB-type signal and modulating it with an artificial message, it would not be difficult for us to find them, using similar techniques to those we have used here.- Vishal Gajjar
So, what does this development mean?
The question of other life in the universe has been near the centre of human interest in the scientific era. At SETI we look for signals of an artificial nature originating from our own galaxy and beyond. Breakthrough Listen also pushes the envelope, using the highest quality instruments, at a range of radio frequencies, to conduct the most sensitive search for intelligent life.
Detecting these pulses originating from a galaxy three billion light years away, at the highest radio frequencies and with the widest bandwidth ever attempted, demonstrated the extraordinary capabilities of our instrument. Such a high-quality instrument can certainly help us explore various other types of signals perhaps produced by intelligent civilizations in our own Milky Way galaxy and beyond. In other words, our discovery gives us confidence in the capabilities of this instrument to conduct a sensitive search for signs of intelligent life in the universe.
Where does your research go from here?
With this discovery, we have sort of sounded an alarm for the entire FRB community that the source is in a new active state, which motivated various other observations from several different telescopes. We are also currently collaborating with different telescopes (from X-ray to various other radio frequencies) around the globe in a campaign to monitor its activity. We have also observed this source at an even higher frequency of up to 12 GHz. I think the next few months are going to be very exciting, with plenty of new observations already being planned.