Fast Radio Bursts: Enigmatic Signals from Across the Universe

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Profile Richard M Lawn
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Message 1984813 - Posted: 12 Mar 2019, 21:10:17 UTC

Astronomers thrive on the appearance of new phenomenon that can stimulate novel theoretical explanations. This often results from the development of an advanced instrument that permits observations that are more sensitive than previous ones, allow us to probe a new time scale, or allow us to see the universe in a new part of the electromagnetic spectrum. But novel discoveries can also come from careful analysis of data already collected by our eyes and ears on the cosmos. SETI efforts, for example, thrive on new ways to find possible signals in the sea of data that you help analyze via SETI@home. In past decades, transient energy bursts at a variety of frequencies have yielded novel classes of astronomical phenomena including pulsars and gamma ray bursts.

In 2007, while searching through archival pulsar survey data collected by the Parkes Radio dish in Australia, Duncan Lorimer and David Narkivic found a sharp radio whistle that descended in frequency for 15 milliseconds. (see the image below from their paper in Science. )

This was the first detection of what were dubbed fast radio bursts (FRB). They searched for more such whistles from that direction in existing data sets and additional observation, but none were found. If it was ET signaling Earth, where was the rest of the message? Some suggested that the burst was an accidental reflection of a mega-energetic pulse of energy meant to push an interstellar light sail, much like our plans for the Breakthrough Starshot program. Or even more fancifully, it might have been a blast from a battle of starships. Of course, a number of explanations due to natural physical phenomenon were also proposed, some of them being rather exotic in their own right. The non-repeating nature of the signal naturally suggested a catastrophic origin, such as the collision of two massive objects or some type of supernova explosion.

Over 100 FRBs have now been detected. The wide scatter of their locations across the sky has been cited as an argument against an extraterrestrial technological source, presuming that aliens would be concentrated in one location. An especially informative discovery was the detection of an FRB source that did repeat its signal many times (roughly 100 repeated bursts have been found). This allowed a series of dedicated observations by many instruments which localized the repeating source to an optically faint irregular galaxy whose red shift placed it 2.5 billion light years away. The distance to other FRBs can be estimated by the nature of the frequency decay during the burst. We know that electromagnetic waves travel through the vacuum at the speed of light. But this represents an upper speed limit. The velocity of visible light is retarded when traveling through glass, water or other media, and the amount of slowing is frequency-dependent. Radio waves emitted from the source of an FRB are also retarded in a frequency-dependent manner as they traverse charged particles both near the source and in the interstellar medium on their way to Earth. Hence the frequency dispersion of the whistle “weighs” the amount of ionized gas between us. Models of the distribution of such intervening ionized gas allows the estimate of the distance to each FRB. All the FRBs measured this way turn out to be well beyond the confines our own Milky Way Galaxy. That means the energy at the source must be enormous. They outshine typical radio blasts from pulsars in our galaxy, yet are millions of times farther away.


Now that astronomers know the type of signal to anticipate, radio telescopes have been humming with searches for more FRBs. In February, the CHIME radio telescope in Canada reported 13 new FRBs, including the second known repeating source. Other radio telescopes including ASKAP in Australia may add hundreds of new detections per year. Both the general distribution of sources (not concentrated in the plane of the Milky Way disc) and their distances estimated from the frequency drift continue to indicate that the current catalog of detected FRBs are all extra-galactic. A local detection would be welcome. None has yet occurred in our galaxy, but such a close FRB could be strong enough to be heard on your cell phone. And the observation of numerous extra-galactic FRBs has an added bonus. The frequency dispersion allows the mapping of ionized gas in the intervening distance that is difficult to detect by other means. This helps to firm up our understanding of the structure and over-all mass distribution of the universe.

A number of models have been proposed to cause FRBs, not only those due to intelligent extra-terrestrials or the opening of nearby microwave ovens (which actually was found to account for one group of potential FRB signals). The collision of massive neutron stars or black holes might fit the bill for one-time FRBs. Such cosmic collisions are known to produce gamma ray bursts and the gravity waves so famously detected by LIGO in recent years. (In this case, repeating and non-repeating FRBs would be distinct phenomenon.) Perhaps a rotating object emits energy in a beam which only sweeps our way transiently, as in the case of pulsars. The observed polarized nature of FRB signals suggest that they arise in a strong magnetic field. This informs the popular theory that they are the product of massive flares arising from stars with magnetic fields dwarfing that of our Sun, which are called magnetars. Magnetars may be neutron stars left over from the explosion that marks the death of massive stars. Our Sun emits much weaker radio bursts when shock waves produced by solar flares travel though its surrounding plasma. A giant cousin of such an event in a more massive compact object could explain the behavior of FRBs. When a giant flair of charged particles rises from its surface it slams into the surrounding debris and the interaction of the shockwave with the strong magnetic field emits a burst of radiation in radio frequencies.

There is a class of super-luminous supernovae of uncertain origin whose explosions could be the parent of such magnetars and the surrounding debris cloud that produce FRBs. Even more exotic astrophysical sources have also been proposed, such as the oscillation of hypothetical cosmic strings produced in the early universe, or other phenomena that stretch the current understanding of relativity and quantum mechanics. While no one model seems to satisfy all of the observations to the point of general acceptance, the study of fast radio bursts is certainly a hot topic for both observational and theoretical astronomers. It also reminds us that the efforts of scientists to expand the capability of detecting and analyzing transient astronomical phenomenon can continue to yield exciting new discoveries, which may someday even include an unequivocal signal from extraterrestrial intelligence.
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Richard M. Lawn
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Message 1984909 - Posted: 13 Mar 2019, 8:44:27 UTC - in response to Message 1984813.  

I'm truly fascinated by the ideas behind these studies. Not the idea of alien lifeforms trying to communicate - it might after all just be an alien opening their microwave oven... but rather I'm fascinated by the idea of extragalactic origins of signals and the distances involved.
It's enough to try and get one's head around the distances involved with our own galaxy but other galaxies? A whole new order.
If one adds to that the idea that light travels at a fairly finite speed apart from being slowed down by gas and so on, then those signals that come from 2.5+ billion light years away are in fact coming to us from the dawn of time.
Which adds another level of complexity to the paradigm.
Then, if you really want this to get more complex, consider that the universe is expanding outwards, and apparently expanding at an accelerating rate and that each part is expanding away from all other parts as well. Kind of like an expanding gas cloud. Then signals arriving here from there to put it simply, are adding a mathematical calculation to the idea that I have no hope of working out. You have a source that is moving away at an ever faster rate, reaching us following, but not quite following ... that source at apparently the same rate but also moving slightly away from the plane of the trajectory of the origin or source of the signal. hmmm.

I'm told that the universe is expanding outward, which indicates a central point, but that we are not "following" objects/galaxies that are further out. There is no 'further out' but rather that every part of the universe is expanding away from all other parts. So this leads me to think that those parts that are closer to the "center" of the cloud are further back in time and that perhaps we can't even see them.
Let me give an example. Strike a match in a still, closed room. Blow it out almost immediately. The smell of the sulpha and the carbon molecules permeate the room in moments. There was a source, but is it possible to locate the source now that the match is out.
So the Big Bang was the match head and we - the carbon molecules, are still expanding to fill the room.


Red-shift and speed

Astronomers see red-shift in virtually all galaxies. It is a result of the space between the Earth and the galaxies expanding. This expansion stretches out the light waves during their journey to us, shifting them towards the red end of the spectrum. The more red-shifted the light from a galaxy is, the faster the galaxy is moving away from Earth. (BBC.com)


So are any galaxies moving toward earth? or at least galaxies moving toward our galaxy?

In any case. A very interesting and thought-provoking article, and while I would think that anyone trying to contact others is more likely to be from a planet in our own galaxy, it adds to the whole project to think that there is no reason at all why intelligent life is not scattered throughout the universe.
Robert Chalmers
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Message 1984990 - Posted: 13 Mar 2019, 21:46:42 UTC - in response to Message 1984813.  

Mr. Lawn,
Thank you for this most interesting and fun post. Please post often here.
Dave Elliott
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Message 1985009 - Posted: 13 Mar 2019, 23:36:54 UTC - in response to Message 1984909.  


So are any galaxies moving toward earth? or at least galaxies moving toward our galaxy?


I think I remember reading that there will be a collision between our galaxy and another or else there was a collision. If there is going to be a collision would that qualify as some galaxy "moving toward earth"?

Tom
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Message 1985513 - Posted: 16 Mar 2019, 18:27:30 UTC - in response to Message 1984909.  

The argument used to express how all galaxies are expanding away from each other, like the blowing up of balloon, finds fault. Example: if all galaxies in the universe are receding from our location, or red-shifted, then how is it predicted that our nearest neighbor, Andromeda, is on a collision coarse with our galaxy? And therein lies the fault. The Milky Way galaxy is roughly 100,000 light years across. Andromeda is roughly 200,000 light years across, at a distance of 2.537 million light years away. When they collide in about 4 billion years, neither galaxy would survive as we know it, and will become the Milkomeda galaxy. I rather doubt there will be actual collisions, as the distance between objects is just too great.

Continuing: either all galaxies everywhere are expanding away from all other galaxies in the universe, or they're not because some of them are on a collision course. I am of the opinion that we are but in the infancy of what we "think" we know, and will have to push the math to exceed current boundaries. I've seen accredited science shows that take the position that no matter where you place your starting point out in space, pick a star, it will always be a position that sees everything else around it expanding away from said location. Well, all except for Andromeda it would seem. No pun intended, but it would appear that there is indeed, a fault in our stars. That's what I love about cosmological study: it never ends. There can never come a time when we know everything. And while I'm betting there are alien life forms out there that are millions of years more advanced than us, money says they don't know everything either, and have to have things aboard their interstellar craft like mechanical and medical bays, toiletries, recycling centers for food, water and air, sleeping quarters, rec rooms, kitchens, and what not.

As for why I would even place my bet on something this, is because in all these years they seem to be stuck with the same technology limiting them to the same type of craft that run around at about the same speed they always have, where Moore's Law seems to concern itself with more than just computer chips, and is what I call the Omega Factor. Having reached the pinnacle of what's obtainable, you concentrate your efforts not on going faster, because no matter how fast you go in the vast expanse of space it will always be slow (such as the limiting factor keeping the speed of light at the cosmological constant of what is 186,000 MPS, even to where it takes light eight minutes to reach the third rock out from its sun, and in the great expanse of space that's no distance at all where every passing minute sees everything else getting that much farther away, but on what amounts to those shortcuts cutting down the distances between point A to point B. And there's only way you do that: you stay interstellar. And even then, it has to be close because, at roughly 60,000 MPH (my estimated top speed of these types of craft,) it would take 4,952,563 years (444 light years/60,000 MPH) just to get from our nearest interstellar neighbor, the Pleiades, to planet Earth at 444 light years in distance.

Yet, things get worse. Imagine, if you will, that you had the technology to travel faster than the speed of light. The instant you went to warp, your spacecraft would no longer have any way to reference anything because the signal going out would still be limited to the speed of light, and would be left in the interstellar dust trying to reach you on the return trip. In fact, it never would. So if it's true that there are galaxies existing on the very outer edge of the universe that are traveling faster than the speed of light, we would never know. Well, all except maybe for the odd, curious FRB (Fast Radio Burst) that's created when the speed of light is exceeded. Exceed even this, what is our imagined warp drive capability, and you would forever be lost in the dark void of what lies outside the known universe with no way back because all of existence is now rendered pitch black, where not even one photon exists beyond the confines of your ship's hull. And although your craft is still traveling many times the speed of light, it's still, for all scientific intent and purposes, forever going nowhere. Even if you hit the brakes, you would still have a lifetime to kill, while waiting for the light you left behind to catch back up with you. Food for scientific thought is all. Na-nu Na-nu.

Genesis
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Message 1985749 - Posted: 18 Mar 2019, 11:46:22 UTC - in response to Message 1984813.  

saludos Richard M Lawn
interesante como siempre tus expresiones y conceptos sobre el tema de las FRB , he reflexionado sobre estas señales y no dejo de pensar en la forma en que se pudiera recibir una señal de radio proveniente de otras áreas del universo. Pensando en un plano o esfera isotropico pudiera entender que son señales atrapadas y que se manifiestan por dentro de esta esfera isotropica , pero también pueden viajar por fuera de esa esfera isotropica ,o sea que puedes escuchar o recibir dos señales a la vez , una mas fuerte que la otra , pero serán siempre la misma señal solo varia la distancia de origen . Es como el efecto rebote de las señales de radio que escuchamos en este transporte que es la tierra , una la escuchamos por vía corta y la otra que es la misma, por la vía larga .
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Message 1985793 - Posted: 18 Mar 2019, 15:19:40 UTC - in response to Message 1984813.  

Thanks for sharing your insight, Mr. Lawn.
TobyB | Blog
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Message 1985818 - Posted: 18 Mar 2019, 16:50:42 UTC - in response to Message 1985749.  

saludos Richard M Lawn
interesante como siempre tus expresiones y conceptos sobre el tema de las FRB , he reflexionado sobre estas señales y no dejo de pensar en la forma en que se pudiera recibir una señal de radio proveniente de otras áreas del universo. Pensando en un plano o esfera isotropico pudiera entender que son señales atrapadas y que se manifiestan por dentro de esta esfera isotropica , pero también pueden viajar por fuera de esa esfera isotropica ,o sea que puedes escuchar o recibir dos señales a la vez , una mas fuerte que la otra , pero serán siempre la misma señal solo varia la distancia de origen . Es como el efecto rebote de las señales de radio que escuchamos en este transporte que es la tierra , una la escuchamos por vía corta y la otra que es la misma, por la vía larga .


I think this is a mechanical translation:

Greetings Richard M Lawn interesting as always your expressions and concepts on the subject of the FRB, I have reflected on these signals and I can not stop thinking about the way in which a radio signal could be received coming from other areas of the universe. Thinking about a plane or isotropic sphere you could understand that they are signals trapped and that they manifest within this isotropic sphere, but they can also travel outside that isotropic sphere, that is, you can hear or receive two signals at once, one more stronger than the other, but they will always be the same signal only varies the distance of origin. It is like the rebound effect of the radio signals that we hear in this transport that is the land, one we hear it by short route and the other one that is the same, by the long way.


Tom
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Message 1986020 - Posted: 19 Mar 2019, 20:59:01 UTC - in response to Message 1985513.  

"Continuing: either all galaxies everywhere are expanding away from all other galaxies in the universe, or they're not because some of them are on a collision course."

That's an absurd reduction. There are local galaxy groups which interact due to gravity, but in general everything we see is rushing away from us. Simple.
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Message 1986084 - Posted: 20 Mar 2019, 9:59:34 UTC

Awesome read Dr. Lawn
Thanks for sharing.
I feel more like an Astrophysicist every time I read your posts!
We are all Alien. It just depends on which planet you are standing on.
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Message 1986891 - Posted: 24 Mar 2019, 13:22:24 UTC - in response to Message 1984990.  

Echoing, "thank you for your great post on FRBs."
And joining the chorus of asking you to please post often here Mr. Lawn.

Carl Kruse
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Message 1987490 - Posted: 27 Mar 2019, 20:54:15 UTC

Why doesn't the space inside galaxies and even solar systems expand at the same rate as the space between galaxies? I understand that the Milky Way and Andromeda are on a collision course but why isn't Andromeda red shifted when viewed minus the gravitational attraction between the two galaxies? Does gravity between two objects prevent the space between them from expanding in some cases? I'm trying to form a working picture in my mind of whats going on.
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Message 1987623 - Posted: 28 Mar 2019, 16:10:50 UTC

Yes, gravity is the overriding force in many cases, such as where relatively nearby galaxies are approaching us, due to our mutual gravitational attraction, and within solar systems, where a star's gravity dominates the scene. The spacetime domain, which contains all the matter in the universe is expanding. This is especially obvious when observing objects a very long way away. The effect of this expansion on the scale of our solar system, or that of nearby galaxies is negligible.
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Message 1988732 - Posted: 4 Apr 2019, 15:13:29 UTC - in response to Message 1984813.  

Interesting pattern. Clearly non-random, but hard to believe that it contains any information, so unsure why any aliens would want to send such a simple burst. Anyway, fascinating article, and good to know that SETI may help to throw some light on these mysterious bursts
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Message 1988738 - Posted: 4 Apr 2019, 15:48:35 UTC - in response to Message 1988732.  

It's just possible that those very brief bursts of radio energy contain a great deal of highly compressed information. It's already been noted that there is 'structure' discernible in some of the bursts. These might not be merely 'simple bursts, after all.
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Message 1988827 - Posted: 5 Apr 2019, 1:10:00 UTC - in response to Message 1985513.  

Excellent post.
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Message 1988840 - Posted: 5 Apr 2019, 2:52:16 UTC - in response to Message 1988827.  

I agree. When seti will find a et life, it will be greatest thing over there
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Message 1988859 - Posted: 5 Apr 2019, 5:32:10 UTC - in response to Message 1985009.  

As mentioned the Andromeda Galaxy will "collide" with the Milky Way Galaxy but the best analogy I can think of is of two smoke rings merging so no actual explosive collision :)
There is anybody out there!
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Message 1989405 - Posted: 10 Apr 2019, 3:14:15 UTC - in response to Message 1988859.  

So probably no collisions or not many of them. What are the chances of a passing star taking our solar system of planets away from our star? Or ruining planetary orbits? Or sending rogue planets smashing through our solar system wreaking havoc?
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Message 1989525 - Posted: 10 Apr 2019, 17:26:23 UTC - in response to Message 1984813.  

Interesting article, but would it be too much to ask to display the text in black on white, rather than white on black? That would be much easier on the eyes, and would avoid most of the wasted ink if we wanted to print a portion for later study.

As a temporary workaround, I highlighted the text with the mouse; this inverts the background and foreground. My eyes didn't strain as much as I read it.

As to the content, I noticed that although differences in light speed through non-vacuous media by frequencies were mentioned as accounting for the changes in frequency of the signals with time (the description sounds like the "chirp" sometimes heard in a Morse code signal, but of course THAT is caused by entirely different phenomena within the transmitter). But Doppler shift wasn't mentioned. Because of the background red shift from cosmic expansion, these "radio" sources may not necessarily have emitted their signals in the radio portion of the spectrum. Was the possibility that some of them may have been bursts of visible light, infrared, ultraviolet, or even gamma rays which were red shifted down to radio frequencies, as the CMB has been shifted.
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Message boards : SETI Perspectives : Fast Radio Bursts: Enigmatic Signals from Across the Universe


 
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