Astronomy News for January 2024: Astronomers are finally beginning to learn something about Fast Radio Bursts (FRBs).

We all know that the cosmic zoo has many weird and wild inhabitants. In addition to the familiar stars, planets, moons, asteroids and comets there are quasars, black holes, neutron stars and brown dwarfs to name just a few. One of the least understood types of objects are known as Fast Radio Bursts (FRBs) which were first discovered in 2007. FRBs are exactly what their name implies, extremely powerful radio emissions that only last for a few thousandths of a second.

Galaxies are just one kind of animal in the Cosmic zoo, but still there are many different types of them! Add in the black holes, supernova, pulsars and etc. and you get quite a plethora of different kinds of objects. (Credit: Futurism)

The fact that FRBs only last around a millisecond makes them very hard to study. Think about it; let’s say a radio astronomer is studying the Andromeda galaxy when out of nowhere, bam there’s a burst of radio energy that’s gone before he can react to it. Hopefully the scientist’s instruments have recorded something but there certainly wasn’t time to make any detailed measurements of the FRB.

A Fast Radio Burst (FRB) is exactly what it sounds like, a short but powerful emission of radio waves from somewhere across the Universe. Like a brief flash of light you see out of the corner of your eyes such things are obviously not easy to study. (Credit: Space.com)

For several years it was thought that FRBs were one offs, that is to say whatever object had generated an FRB would never generate another. Just a couple of years ago however the first repeating FRBs were identified and now it is thought that astronomers have identified about 50 repeating FRBs. The question then is whether all FRB sources are actually repeaters, although with different time scales.

Actual measured data from an FRB. (Credit: Centre for Astrophysics and Supercomputing)

Recognizing some FRBs as periodic has allowed radio astronomers to train their instruments on a known repeater and then just wait to catch the full event. Recently this technique has enabled astronomers to catch the furthest ever seen FRB at a distance of about 8 billion light years away. To be able to be heard from such an enormous distance the FRB, which has been given the designation FRB 20220610A, had to pack as much energy as our Sun emits in 30 years into a pulse less that one thousandth of a second.

Hubble Space Telescope image of the host galaxy of FRB 20220610A. Most of the other objects in this image are galaxies as well, each one a home to billions of stars. Makes ya feel kinda small! (Credit: Hubblesite.org)

Although there is a great deal that is still unknown about FRBs a consensus of opinion is growing that FRBs are generated by neutron stars with extremely strong magnetic fields known as magnetic-stars or magnetars. (See my post of 21November 2020 concerning neutron stars) Neutron stars are the remnants of big stars, at least 10 times the mass of our Sun, that have exploded as supernovas., Whatever is left, about the mass of our Sun, is crushed down to a size about 20-40km in diameter, becoming in a sense a big atomic nucleus made almost exclusively of neutrons. Even though astronomers have begun to agree on the source of FRBs however there was still a debate over how magnetars stars generated the radio outbursts, the two leading candidates being either something like a solar flare or some kind of starquake in the magnetar’s surface.

One theory for how FRBs are generated proposes that flares released by highly magnetic neutron stars (Magnetars) collide with matter released from previous flares. Some of the energy of that collision is emitted as intense radio waves. (Credit: CivilsDaily)

Recently a new study by Tomonori Totani and Yuya Tsuzuki at the University of Tokyo’s Department of Astronomy has compared the time and energy distribution of some 7,000 FRBs from those 50 repeating sources to seismic measurements of nearly 6,000 Earthquakes from Japan. What the two found was several similarities between the two sets of data, especially when it came to aftershocks. In summary the similarities were:

1. The probability for an aftershock occurring was 10-50%

2. The probability for an aftershock decreased with time as a power of time.

3. The probability for an aftershock remains constant even as the mean rate of the original FRB changes.

4. There is no correlation between the energies of the main FRB and any aftershocks.

We’re all aware of the power of an Earthquake. Just imagine such a thing happening on a neutron star! (Credit: New Straights Times)

On the other hand the astronomers found no relationship between FRBs and solar flares. This analysis strongly suggests that FRBs are generated by starquakes on the surface of magnetars. If that is true then we may be able to use the data from FRBs to help us better understand these ultra-dense onjects.

Almost beyond imagination is the idea of a quake on an object as massive as our Sun yet as small as a city. (Credit: Scienceline)

Doctors Totani and Tsuzuki intend to continue their analysis, hoping that further measurements from more FRBs may tell us more about FRBs and the weird cosmic wonders that generate them.

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