Missing Matter’ Breakthrough With Rare Capture Of Fast Radio Burst

CSIRO’s Parkes radio telescope catches a FRB in real-time. (Swinburne Astronomy Productions)
CSIRO’s Parkes radio telescope catches a FRB in real-time. (Swinburne Astronomy Productions)

The 64-m Parkes radio telescope of the Commonwealth Scientific and Industrial Research Organization (CSIRO), Australia, detected a fast radio burst (FRB) on April 18, 2015. The detection of the FRB triggered an international alert for prompt follow-up with other telescopes around the world.

Within hours, high-end telescopes including Australia Compact Array (ATCA) of CSIRO, Australia, and Effelsberg Radio Telescope, Germany were scouring for the detected FRB signal.

But why this much fanfare for a rare occurrence in the stars?

Fast Radio Bursts (FRBs)

FRBs are incredibly rare, very difficult to detect, and conceal lots of valuable information about the nature of the universe. They are mysterious bright radio flashes that last for only a few milliseconds. For now, their origin remains a mystery, although there are plenty of theories on how or why they come about.

The SUPERB project

Before April 18, 2015, scientists had only detected 16 FRBs. Interestingly, these 16 FRBs were not revealed by an active telescope. Scientists found them by sifting through recorded data, several months/years after they had occurred.

This made studying FRBs an uphill task, because by the time scientists discover them, it is often too late to perform follow up observations. Therefore, quick detection of FRBs was necessary. This led to the development of the Survey for Pulsars and Extragalactic Radio Bursts (SUPERB) project.

The international research team behind the project includes scientists from the Max Planck Institute for Radio Astronomy (MPIfR) in Bonn, Germany. The project uses a combination of radio and optical telescopes to detect FRBs within seconds, identify the precise location of the FRB, and immediately alert other telescopes to search for more evidence in the aftermath of the initial flash, when there is still time.

Fast Radio Burst
The infrared image on the left shows the field of view of the Parkes radio telescope with the area where the signal came from marked in cyan. On the right are successive zoom-ins. At the bottom right is the Subaru optical image of the FRB galaxy, with the superimposed elliptical regions showing the location of the fading 6-day afterglow seen with ATCA. Credit: D. Kaplan (UWM), E. F. Keane (SKAO)

The rare FRB occurrence

After the 64-m Parkes telescope of the CSIRO detected the FRB, the six 22-m dishes of the ATCA, also managed by the CSIRO, enabled the research team to pinpoint the location of the FRB signal, and detected a radio afterglow related to the event.

The radio afterglow lasted for around 6 days before fading away. Within that time, the team was able to pinpoint the location of the FRB with an outstanding accuracy that is 1000 times more precise than for previous FRB events.

Going forward, the team then used the 8.2-m Subaru optical telescope of the National Astronomical Observatory of Japan (NAOJ), Hawaii, to resolve the location of the occurrence to an elliptical galaxy that is 6 billion light years away from Earth.

According to lead scientist, Evan Keane, this is the first time scientists are able to identify the host galaxy of an FRB and the distance of the host galaxy from Earth.

Scientists were also able to find out more about the FRB like figuring out that it is not a repeater, but rather the result of a cataclysmic event in that distant galaxy.

The ‘missing matter’ breakthrough

However, by far the most important application of data from the FRB occurrence was comparing the FRB-sourced frequency-dependent dispersion with the current model of the distribution of matter in the Universe.

The aim of the comparison, according to co-author Simon Johnston, was to enable scientists weigh the Universe, or at least weigh the normal matter in the Universe.

According to estimates backed by the current model of distribution, the Universe contains 70% dark energy, 25% dark matter, and 5% ‘ordinary matter’. ‘Ordinary matter’ refers to matter that makes everything we see.

However, astronomers through innumerable observations of hydrogen, stars, and galaxies had only been able to account for around half of the ordinary matter. Since scientists could not see the remainder directly, scientists had dubbed these invisible ordinary matter as ‘missing.’

That is until the SUPERB team’s observations of the April 2015 FRB and the model matched, thus revealing the elusive ‘missing matter.’ Marking the first time scientists use an FRB to conduct a cosmological measurement.

Immense potential of FRBs

The ‘missing matter’ breakthrough uncovers the immense potential of FRBs as new tools for cosmology. As scientists position the Square Kilometer Array to detect more FRBs and pinpoint their host galaxies, scientists are hopeful a larger sample will enable precise measurements of cosmological parameters like the distribution of matter in the Universe as well as provide a better understanding of dark energy.