Ask an Astronomer: What Are Mysterious Fast Radio Bursts? Pragya Chawla Demystifies FRBs, CHIME Telescope, and More | The Weather Channel – Articles…

The cosmic universe is full of unknown, exciting mysteries! Among all, a relatively recent phenomenon of Fast Radio Bursts, and its repeated detection, has attracted immense global attention. These are the intense bursts of radio emissions from unknown origins and last for only milliseconds, making it difficult to study them.

Astronomers observed the first traces of FRBs while examining archival data of Magellanic clouds pulsar survey in 2007. As per the data from the US space agency NASA, astronomers have recorded more than 1,000 FRBs originating from various sources since then. More than 15 of them have also been associated with galaxies other than our own.

To know more about this mysterious phenomenon, The Weather Channel spoke to Pragya Chawla, a research scholar at McGill University, Canada. She is among a few leading astronomers studying FRBs and rotating radio transients using Green Bank Telescope and CHIME (Canadian Hydrogen Intensity Mapping Experiment). Heres what she had to say about the phenomenon:

Fast Radio Burst have attracted significant traction in recent years. Can you briefly explain what they are and what their scientific importance is?

An infographic showing the path of FRB 18112 passing through the halo of an intervening galaxy.

Fast radio bursts (or FRBs) are bright flashes of radio light, lasting for microseconds to milliseconds. These bursts are so bright that they can be detected on Earth even though they are located in galaxies billions of light-years away from us.

On their way to Earth, the radio waves emitted by FRBs interact with electrons and magnetic fields. These interactions get imprinted in the properties of FRBs. FRBs can thus be used as cosmological probes and help us study the material located between galaxies.

If FRBs last only a few milliseconds, how do scientists study these signals? What are the challenges?

We study these signals using radio telescopes located on Earth that can point to different locations in the sky. These telescopes have extremely sensitive antennas which can measure changes in the brightness of radio light every millisecond. The challenge lies in processing the large amounts of data recorded by these telescopes.

The antennas can detect signals produced by microwaves, cellphones, aeroplane transmitters and other devices. Our detection algorithms have to be carefully designed so that they can distinguish FRBs from terrestrial signals.

How does the CHIME telescope detect these strange signals? What is the working mechanism of such telescopes?

CHIME telescope

The CHIME telescope is made up of four half-cylinderseach 100 metres in length and 20 metres in diameter. Each cylinder is fitted with 256 antennas. Radio waves from the sky are reflected by the surface of these cylinders and directed towards the antennas. The signals from the antennas are processed by hundreds of GPUs and amount to a data rate of 7 Terabits per second. This data rate is about 5% of the global mobile data traffic.

In 2007, the discovery of FRBs came as a surprise for the scientific community. Why was such a phenomenon not predicted before?

The discovery came as a surprise because FRBs are a million times more energetic than any bursts of radio emission we had observed from neutron stars in our galaxy. There are so many known astrophysical explosions (supernovae, merging stars, flares from magnetars etc.) that it is hard to predict every phenomenon that these sources could show. It is common for theoretical predictions to inspire observations, but it is great that in the field of FRBs, observations lead to so many theories being proposed!

Despite years of research on the source of FRBs, theories range from neutron star circles to cataclysmic cosmic collisions. What is the current scientific consensus on the origin of FRBs? What are the lingering mysteries?

Artist's impression of SGR 1935+2154, a highly magnetised stellar remnant, also known as a magnetar.

We think that at least some fraction of FRBs is produced by highly magnetised neutron stars or magnetars. Neutron stars are the cores of massive stars that collapsed onto themselves. The consensus that magnetars could produce FRBs emerged after the detection of an FRB-like burst from a magnetar in our own Galaxy in April 2020. We still don't know whether magnetars produce all FRBs.

Also, some FRBs are observed to repeat, i.e. bursts are detected from the same sky location after several weeks or months. We don't yet know whether repeating, and non-repeating FRBs originate from the same type of astrophysical object. There are many more unanswered questions, which is why it is an exciting time to study these bursts!

Tell us a bit about your research on FRBs.

As a member of the CHIME/FRB collaboration, I study FRBs using the CHIME telescope. Specifically, I work on understanding the propagation effects, i.e. properties of FRBs that change as their signals travel through the intervening medium. This allows us to study the environments that FRBs are located in and the medium between galaxies in great detail. I also characterise the time CHIME spends on each sky position and use it to understand how often FRBs burst.

Recently, CHIME detected the largest cache of FRBs that could signify some of its distinct features. Could you tell us more about this?

Artist's impression of a magnetar in outburst, showing complex magnetic field structure and beamed emission, here imagined as following a crust cracking episode.

CHIME detected 535 bursts in its first year of operations. For comparison, the total number of FRBs discovered in the decade before CHIME started operating was 60. Such a large number of detections led us to calculate how often FRBs burst. We estimate that 800 FRBs are happening in the sky each day. We dont detect all of these bursts with CHIME as it only sees 1% of the sky at any time.

We also found that FRBs that repeat are different from those that burst only once. Repeating FRBs emit bursts of longer duration, and the radiation is detected in a narrower range of frequencies. This discovery could suggest that repeating and non-repeating FRBs are located in different astrophysical environments or are generated by different astrophysical objects.

As space exploration continues to gain very high importance this decade, especially in terms of space tourism, what should be of the highest priority for the scientific community?

With regards to space exploration, it's great that we are exploring our solar system with missions such as the recently launched Perseverance rover. It is also important to expand our research efforts to locate the nearest habitable planets beyond the solar system. As we explore our local neighbourhood, we shouldn't lose sight of the big picture and continue to develop an understanding of the evolution of the universe.

The interview is a part of a series titled Ask An Astronomer. Here is the last interview of this series:

Prof P Ajith Explains How Studying Gravitational Waves Can Enrich Our Understanding of Universe

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Ask an Astronomer: What Are Mysterious Fast Radio Bursts? Pragya Chawla Demystifies FRBs, CHIME Telescope, and More | The Weather Channel - Articles...