• Home
  • /
  • Astronomy
  • /
  • Mysteries of our universe – Fast Radio Bursts (FRBs)
Picture credit - AASNOVA
Picture Credit - AAS Nova

Mysteries of our universe – Fast Radio Bursts (FRBs)

Astronomy, the science of the physical universe is limited only by human perception. We have been able to explore our surroundings based on what we perceive as the physical universe. The guide for this perception is electromagnetic radiation, and anything beyond the boundaries of electromagnetic radiation is an unknown to the human species.

Photo Credit – Wikipedia

Within electromagnetic radiation we depend to a greater extent on a particular frequency of waves called as ‘radio waves’, they operate in the range of 300 GHz and 3kHz with a wavelength that ranges between 1mm and 100km. When you look at the electromagnetic spectrum, these waves occupy the lowest portion amongst all other signals.

A brief history of radio astronomy

For most of human history, astronomers have depended on visible light and optical telescopes to observe the observable universe until radio telescopes were invented in 1932 by Karl Guthe Jansky at Bell laboratories. Karl’s radio telescope was more a radio antenna made out of an array of dipoles and reflectors to receive shortwave radio signals and was built to identify sources that were interfering with radiotelephone signals. An amateur radio astronomer by name Grote Reber further optimised this concept who later came to be known as one of the pioneers in the field of radio astronomy. Grote built the first parabolic ‘dish’ 9m in diameter in his backyard.

A segue from this brief history of the radio telescope is the practical applications and discoveries being made by this device in our present times. Today arrays of radio telescope around the world are helping astronomers understand the characteristics of celestial bodies in our immediate surroundings and also far outside our Milky Way galaxy. These telescopes can detect thermal radiation from solid bodies such as planets, interstellar hot gas mediums, synchrotron radiation from electrons in weak magnetic fields, spectral line radiation from atomic transitions in gaseous envelops around stars and pulsed radiation from rapidly rotating neutron stars. Using radio telescopes equipped with sensitive spectrometers, radios astronomers have discovered chemical compounds such as water, formaldehyde, ethyl alcohol, ammonia, methanol and carbon dioxide.

Fast Radio Bursts

One of the fascinating phenomenon captured by radio astronomers in the recent past is a Fast Radio Burst also know as FRB. FRBs are high energy signals detected by radio telescopes lasting not more than a few milliseconds. What makes these signals quite intriguing is that we are yet to understand the origins of this signal. The definition of FRBs found on the Internet is as follows:

[mks_pullquote align=”centre” width=”800″ size=”18″ bg_color=”#b9d6ad” txt_color=”#000000″]“Fast radio bursts are bright, unresolved (point-source-like), broadband (spanning a large range of radio frequencies), millisecond flashes found in parts of the sky outside the Milky Way.”[/mks_pullquote]

The burst usually appears as a single spike of energy without any change in its strength over time. The bursts last for a period of several milliseconds (thousandths of a second). The bursts come from all over the sky and not concentrated on the plane of the Milky Way.

The burst usually appears as a single spike of energy without any change in its strength over time. The bursts last for a period of several milliseconds (thousandths of a second). The flashes come from all over the sky and not concentrated on the plane of the Milky Way. The nature and the origins of these FRBs have given rise to a lot of speculation. Astronomers have not been able to understand the source of FRBs however fully. Theoretically, they seem to originate in the surroundings of a dense neutron star or a black hole. The irony is that we don’t have a complete understanding of the characteristics of both the black hole and neutron stars.

Discovery of FRBs

Since 2007 radio astronomers have been able to detect FRBs from around 30 sources, and the vocabulary used to identify them is based on the date of discovery in the format “FRB YYMMDD”.

The first FRB called  Lorimer Burst FRB010724 was discovered in 2007 when Duncan Lorimer assigned his student David Narkevic to look through archival data taken in 2001 by the Parkes radio dish in Australia.

FRB 121102

These radio transmissions have been one-off events from individual sources until in 2012 FRB 121102 was detected in the direction of constellation Auriga in the northern hemisphere using the Arecibo radio telescope. In November 2015, astronomer Paul Scholz at McGill University in Canada found ten non-periodically repeated fast radio pulses in archival data gathered in May and June 2015 by the Arecibo radio telescope from the same source that broadcasted FRB 121102.

As of January 2017, FRB 121102 is thought to be co-located in a dwarf galaxy about three billion light-years from earth with a low-luminosity active galactic nucleus, or a previously unknown type of extragalactic source, or a young neutron star energising a supernova remnant.

On 26 August 2017 the Breakthrough Listen project using the Green Bank Telescope in West Virginia and a Dutch team using the William E Gordon Telescope at the Arecibo Observatory in Puerto Rico simultaneously identified 16 new bursts during a 10-hour period.

They were able to identify distortions in the signals that led to believe that these radio waves were highly polarised (highly twisted-transverse waves) and that can only happen when the messages come under the influence of a cosmic body which has an incredibly strong magnetic core.

FRB 121102 and its connection to Alien life theories

One of the more popular theories for the origin of FRBs until 2017 was that it could be signals generated by collisions of extremely dense magnetic core cosmological bodies such as neutron stars and black holes. Since the source never repeated the message, this theory was widely accepted and compared to gamma-ray bursts. However, the discovery of repeated bursts from FRB 121102 has squashed this theory. In the case of FRB 121102 radio astronomers calculated that the source must be emanating as much energy as 500 million suns in the space of a millisecond, to explain how it was still detectable three billion years after the event. Quite clearly, astronomers do not yet understand the circumstances under which neutron stars would unleash such powerful blasts of radiation.

The uncertainty of a plausible explanation has resulted in an idea that these signals are broadcasts from an alien civilisation. Scientists cannot refute the fact that this is one of the more potential candidates for communication with a life that is not Earth. Since the signal is extremely short and lasts only a few milliseconds, current technology does not give us the tools to get anything meaningful in decoding the message. However, advanced alien civilisations could communicate in far smaller pieces of code than what we are accustomed to deciphering.

A more rational explanation

Radio telescopes from all over the world are pointed in the direction of FRB 121102 trying to find a more logical answer to the phenomenon. Recently a group of researchers presented their findings at the 231st meeting of the American Astronomical Society, and their paper is available in the journal Nature. According to their research, FRB 121102 inhabits an extreme magneto-ionic environment. Links to this journal has been provided as footnotes on this blog for your reference.

Another train of thought is that astronomers may have overestimated the amount of energy expelled from this source, as it is possible that the magnetic field acts as a form of cosmic magnifying glass, making the source appear ten or 100 times brighter than the fact.

No matter where the research leads to; this is an exciting time in the field of radio astronomy. The mystery of fast radio bursts is a bounty waiting to be snatched by the right explanation.

Further Reading

Leave a Reply