New Fast Radio Burst Discovery Finds 'Missing Matter' In the Universe (phys.org)

According to a study published today, an international team of scientists has for the first time managed to identify the location of a fast radio burst. FRBs are bright radio flashes that generally last for a few milliseconds. While their origin is unknown, the results are a missing distribution of matter in the universe. Now, using a combination of radio and optical telescopes, scientists have found the FRB. According to Benjamin Stappers, Professor of Astrophysics at the University of Manchester, "Discovering more FRBs will allow us to do even more detailed studies of the missing matter and perhaps even study dark energy."

Comments

Lecture from Virginia Tech

[coastwalker]

https://www.youtube.com/watch?... Fast Radio Bursts

Looks at the hardware challenges

"Published on Nov 6, 2015

Fast radio bursts (FRBs) are mysterious single pulses recently discovered in routine L-band pulsar searches. They are very brief (~milliseconds), and exhibit dispersion and spatial distribution which suggests large -- possibly cosmological -- distances. Although they probably occur at a rate of about 10,000/sky/day, they are quite difficult to find due to the very narrow field of view of suitably-equipped radio telescopes, and also due to the prevalence of interference at L-band. In this talk I will give an overview of instrumentation that has been developed to detect FRBs in large numbers and with better information (polarization, improved localization, etc.). In particular I will describe GBTrans, a new instrument we (VT, WVU, and NRAO) have developed at Green Bank for continuous real-time FRB searching, and plans for a new instrument called LASA (Large Array of Small Arrays), which would be purpose-built for this task. Both systems feature real-time continuous acquisition and analysis of about 400 MHz of L-band spectrum, using FPGAs to compute dynamic spectra and GPUs to search 1000s of possible dispersion signatures simultaneously. LASA would replace the GBTrans 20-m dish antenna with 2 m x 2 m arrays of 256 tightly-coupled crossed dipole antennas each, forming 16 independently-steerable beams simultaneously. This problem requires mitigation of copious interference from active users of the L-band spectrum, and I'll explain how we manage to do that in real time as well."

Found the missing _baryons_

[StupendousMan]

Astronomers have known for years that the ordinary matter we see every day -- made up of protons, electrons, and neutrons -- can only make up a small fraction of the mass-energy density needed to explain the large-scale structure of the universe. This ordinary, or "baryonic" matter, makes up around 4% of the critical amount. Another 23% or so is "dark matter", which isn't made of protons, electrons or neutrons, but does exert gravitational forces like baryonic matter; and the remaining 73% or so is the very mysterious "dark energy", which acts sort of like anti-gravity.

When most scientists see the phrase "missing matter", they think of the "dark matter" portion of the universe -- the 23%.

But this new result gives us information on a portion of the 4%, the ordinary baryonic matter. We think it should make up 4% of the critical density because of the relative abundances of hydrogen, helium, and lithium which were produced soon after the Big Bang ... but when we add up the stuff that we can see with telescopes -- stars and gas -- we find only about 1% of the critical amount. So, about 3% of the baryons were hiding somewhere.

This new study looked at radio waves from an event in a very distant galaxy. Those radio waves had to traverse a very long distance to reach us. As they flew through space, IF that space had even very thin traces of gas, waves of some frequencies would travel just a bit faster than others. That dispersion in frequency acts to spread out the arrival of the radio waves by the time they reach the Earth. The astronomers mentioned here observed a small spread in arrival times and used to to figure out how much gas the waves must have encountered in between the galaxies. The result: just the right amount of gas to account for all those hidden baryons.

So, yes, this study found missing baryons. It did not produce any direct measurements of dark matter or dark energy. On the other hand, if we can pinpoint other fast radio bursts in the future and study their host galaxies, we may learn something about those other entities, too.

Re:I thought

[DrJimbo]

Nope. The mass of the universe universe is 70% dark energy, 25% dark matter, 5% familiar matter. But only about half of that 5% can be accounted for by direct observation - the rest is "missing".

Correct.

TFA claims that the radio burst let researchers find a very dim (radio) galaxy that would not have otherwise been found - the matter is "missing" simply because you have to point a very good telescope at exactly the right part of the sky for a long time to find it.

Incorrect. It doesn't even make sense that finding one more galaxy would somehow account for half the normal mass of the Universe. Finding the originating galaxy was part of the solution but it helped because it gave them the distance to the FRB source. They already knew the dispersion (different frequencies arriving at different times) of the FRB. The dispersion tells you how much non-dark matter the signal passed near during its trip here. By also knowing the distance to the source, they were able to calculate the average density of the non-dark matter along the line of travel. This average density was then be used to estimate the amount of non-dark matter in the Universe.