Fast radio bursts may be firing off everysecond21 September 2017

This artist's impression shows part of the cosmic web, afilamentary structure of galaxies that extends across theentire sky. The bright blue, point sources shown here arethe signals from Fast Radio Bursts (FRBs) that mayaccumulate in a radio exposure lasting for a fewminutes. The radio signal from an FRB lasts for only afew thousandths of a second, but they should occur athigh rates. Credit: M. Weiss/CfA

When fast radio bursts, or FRBs, were firstdetected in 2001, astronomers had never seenanything like them before. Since then, astronomershave found a couple of dozen FRBs, but they stilldon't know what causes these rapid and powerfulbursts of radio emission.

For the first time, two astronomers from theHarvard-Smithsonian Center for Astrophysics (CfA)have estimated how many FRBs should occur overthe entire observable universe. Their workindicates that at least one FRB is going offsomewhere every second.

"If we are right about such a high rate of FRBshappening at any given time, you can imagine thesky is filled with flashes like paparazzi takingphotos of a celebrity," said Anastasia Fialkov of theCfA, who led the study. "Instead of the light we can

see with our eyes, these flashes come in radiowaves."

To make their estimate, Fialkov and co-author AviLoeb assumed that FRB 121102, a fast radio burstlocated in a galaxy about 3 billion light years away,is representative of all FRBs. Because this FRBhas produced repeated bursts since its discovery in2002, astronomers have been able to study it inmuch more detail than other FRBs. Using thatinformation, they projected how many FRBs wouldexist across the entire sky.

"In the time it takes you to drink a cup of coffee,hundreds of FRBs may have gone off somewherein the Universe," said Avi Loeb. "If we can studyeven a fraction of those well enough, we should beable to unravel their origin."

While their exact nature is still unknown, mostscientists think FRBs originate in galaxies billions oflight years away. One leading idea is that FRBs arethe byproducts of young, rapidly spinning neutronstars with extraordinarily strong magnetic fields.

Fialkov and Loeb point out that FRBs can be usedto study the structure and evolution of the Universewhether or not their origin is fully understood. Alarge population of faraway FRBs could act asprobes of material across gigantic distances. Thisintervening material blurs the signal from the cosmic microwave background (CMB), the left overradiation from the Big Bang. A careful study of thisintervening material should give an improvedunderstanding of basic cosmic constituents, suchas the relative amounts of ordinary matter, darkmatter and dark energy, which affect how rapidlythe universe is expanding.

FRBs can also be used to trace what broke downthe "fog" of hydrogen atoms that pervaded the earlyuniverse into free electrons and protons, whentemperatures cooled down after the Big Bang. It isgenerally thought that ultraviolet (UV) light from the

1 / 3

first stars traveled outwards to ionize the hydrogengas, clearing the fog and allowing this UV light toescape. Studying very distant FRBs will allowscientists to study where, when and how thisprocess of "reionization" occurred.

"FRBs are like incredibly powerful flashlights thatwe think can penetrate thise fog and be seen overvast distances," said Fialkov. "This could allow usto study the 'dawn' of the universe in a new way."

The authors also examined how successful newradio telescopes – both those already in operationand those planned for the future – may be atdiscovering large numbers of FRBs. For example,the Square Kilometer Array (SKA) currently beingdeveloped will be a powerful instrument fordetecting FRBs. The new study suggests that overthe whole sky the SKA may be able to detect morethan one FRB per minute that originates from thetime when reionization occurred.

The Canadian Hydrogen Intensity MappingExperiment (CHIME), that recently beganoperating, will also be a powerful machine fordetecting FRBs, although its ability to detect thebursts will depend on their spectrum, i.e. how theintensity of the radio waves depends onwavelength. If the spectrum of FRB 121102 istypical then CHIME may struggle to detect FRBs.However, for different types of spectra CHIME willsucceed.

The paper by Fialkov and Loeb describing theseresults was published in the September 10, 2017issue of The Astrophysical Journal Letters, and isavailable online.

More information: Anastasia Fialkov et al. A FastRadio Burst Occurs Every Second throughout theObservable Universe, The Astrophysical Journal(2017). DOI: 10.3847/2041-8213/aa8905 , arxiv.org/abs/1706.06582

Provided by Harvard-Smithsonian Center forAstrophysicsAPA citation: Fast radio bursts may be firing off every second (2017, September 21) retrieved 12 July2022 from https://phys.org/news/2017-09-fast-radio.html

2 / 3

This document is subject to copyright. Apart from any fair dealing for the purpose of private study or research, nopart may be reproduced without the written permission. The content is provided for information purposes only.

Powered by TCPDF (www.tcpdf.org)

3 / 3