Astronomers may have finally found the origin of radio waves discovered a decade ago, in a highly magnetised gas filled region of space, outside of the galaxy. The findings found within database records suggest other examples of particular radio waves may be discovered within this archival data in the future.
A new class of radio wave known as fast radio bursts FRBs were discovered in the last decade, a high energy astrophysical phenomenon which contains a transient radio pulse lasting only a fraction of a second. With the origin of these bursts being previously unknown, astronomers speculated FRBs may originate from other stars or even be evidence of extra-terrestrial intelligent life. A more likely explanation by Loeb and colleagues argued the bursts might be from extremely energetic events, for example the collapse of a neutron star into a black hole, the resultant waves may travel billions of light years. Stellar flares and two types of star might be a source; a small mass star or solar-mass “contact” binaries which orbit so closely to each other they may influence each other, both types of star may significantly fluctuate in the level of light emitted. Earlier research suggested the radio bursts had energy to come from within the milky way galaxy however, contact binary systems may be a source of FRBs from within the milky way.
A new study by Masui and colleagues (3) may have indicated where the FRBs originated. After analysing 650 hours of archival data the team discovered the most detailed record ever found of a FRB. The team found the FRB by using specialist software created by Masui and Jonathan Sievers from the university of Kwazulu-Natal in Durban, South Africa. A challenging task of analysing 40 terabytes of information ensued with the additional smearing out of the FRB signal due to its journey through space, intensifying this. Findings indicate the signal to have originated around 6 billon light years away based on dispersion delay, this estimates the distance radio waves may have travelled, although this may also cloud the detection of an FRB. The new software cancelled out the effects of dispersion and restored the burst to its original form.
One particular signal with greater polarisation information became isolated due to its rare makeup, “Hidden within an incredibly massive dataset, the team found a very peculiar signal, one which matched all the known characteristics of a fast radio burst, [although] with a tantalising extra polarisation element far from seen before” commented Jeffrey Peterson, co-author. Polarisation an element of electromagnetic radiation includes light and radio waves and indicates the orientation of a wave. The team used these findings to demonstrate the FRB displayed faraday rotation, a magneto-optical phenomenon which rotates the polarisation of the wave, the twisting radio waves may be acquired by passing through a powerful magnetic field.
“This tells astronomers something about the magnetic field the burst travelled through on its way to Earth, giving a hint about the burst’s environment” said Masui. “It also gives theorists a bit more to work with when coming up with explanations for these bursts.”
Measurements of the dispersion delay show the FRBs more than likely originated in another galaxy and this also rules out the bursts being created in the galaxy. The team may have shown how the signal probably passed through two regions of ionised gas called “screens” during its journey to Earth. Additionally, the location of the source of the signal may have been pinpointed using data of the location and interplay of the screens; at around a hundred thousand light years away. The research shows how the burst originated in a highly magnetised region of space, maybe characteristic of a supernova or an active star forming nebula.
“Taken together, these remarkable data reveal more about an FRB than have ever been seen before and give important constraints on these mysterious events. An exciting new tool is also now available to search through otherwise overwhelming archival data to uncover more examples and get closer to truly understanding the nature of FRBs.” Said Masui.
What other types of communication may be capable of being received from outer space?