by BeAChooser » Tue Mar 07, 2023 5:47 pm
https://earthsky.org/space/cosmic-burst ... r-mystery/
Has mystery of universe’s missing matter been solved?
What it boils down to is that up till now they've found only about half the ordinary matter they claimed there should be back in the late 1990s. But using fast radio bursts, they appear to have found the rest. Here's what they realized back in 2007 ...
As these bursts of radiation traverse the universe and pass through gases and the theorized WHIM, they undergo something called dispersion.
The initial mysterious cause of these FRBs lasts for less a thousandth of a second and all the wavelengths start out in a tight clump. If someone was lucky enough – or unlucky enough – to be near the spot where an FRB was produced, all the wavelengths would hit them simultaneously.
But when radio waves pass through matter, they are briefly slowed down. The longer the wavelength, the more a radio wave “feels” the matter. Think of it like wind resistance. A bigger car feels more wind resistance than a smaller car.
The “wind resistance” effect on radio waves is incredibly small, but space is big. By the time an FRB has traveled millions or billions of light-years to reach Earth, dispersion has slowed the longer wavelengths so much that they arrive nearly a second later than the shorter wavelengths.
Therein lay the potential of FRBs to weigh the universe’s baryons, an opportunity we recognized on the spot. By measuring the spread of different wavelengths within one FRB, we could calculate exactly how much matter – how many baryons – the radio waves passed through on their way to Earth.
At this point we were so close, but there was one final piece of information we needed. To precisely measure the baryon density, we needed to know where in the sky an FRB came from. If we knew the source galaxy, we would know how far the radio waves traveled. With that and the amount of dispersion they experienced, perhaps we could calculate how much matter they passed through on the way to Earth?
Unfortunately, the telescopes in 2007 weren’t good enough to pinpoint exactly which galaxy – and therefore how far away – an FRB came from.
So fast forward to today's technology and instruments ...
It was 11 years until we were able to place – or localize – our first FRB. In August 2018, our collaborative project called CRAFT began using the Australian Square Kilometre Array Pathfinder (ASKAP) radio telescope in the outback of Western Australia to look for FRBs. … snip …
ASKAP captured its first FRB one month later. Once we knew the precise part of the sky the radio waves came from, we quickly used the Keck telescope in Hawaii to identify which galaxy the FRB came from and how far away that galaxy was. The first FRB we detected came from a galaxy named DES J214425.25–405400.81 that is about 4 billion light-years away from Earth, in case you were wondering.
The technology and technique worked. We had measured the dispersion from an FRB and knew where it came from. But we needed to catch a few more of them in order to attain a statistically significant count of the baryons. So we waited and hoped space would send us some more FRBs.
By mid-July 2019, we had detected five more events, enough to perform the first search for the missing matter. Using the dispersion measures of these six FRBs, we were able to make a rough calculation of how much matter the radio waves passed through before reaching Earth.
We were overcome by both amazement and reassurance the moment we saw the data fall right on the curve predicted by the 5% estimate. We had detected the missing baryons in full, solving this cosmological riddle and putting to rest two decades of searching.
In my opinion, this is how science is supposed to work.
[url]https://earthsky.org/space/cosmic-bursts-unveil-universe-missing-matter-mystery/[/url]
[quote]Has mystery of universe’s missing matter been solved?[/quote]
What it boils down to is that up till now they've found only about half the ordinary matter they claimed there should be back in the late 1990s. But using fast radio bursts, they appear to have found the rest. Here's what they realized back in 2007 ...
[quote]As these bursts of radiation traverse the universe and pass through gases and the theorized WHIM, they undergo something called dispersion.
The initial mysterious cause of these FRBs lasts for less a thousandth of a second and all the wavelengths start out in a tight clump. If someone was lucky enough – or unlucky enough – to be near the spot where an FRB was produced, all the wavelengths would hit them simultaneously.
But when radio waves pass through matter, they are briefly slowed down. The longer the wavelength, the more a radio wave “feels” the matter. Think of it like wind resistance. A bigger car feels more wind resistance than a smaller car.
The “wind resistance” effect on radio waves is incredibly small, but space is big. By the time an FRB has traveled millions or billions of light-years to reach Earth, dispersion has slowed the longer wavelengths so much that they arrive nearly a second later than the shorter wavelengths.
Therein lay the potential of FRBs to weigh the universe’s baryons, an opportunity we recognized on the spot. By measuring the spread of different wavelengths within one FRB, we could calculate exactly how much matter – how many baryons – the radio waves passed through on their way to Earth.
At this point we were so close, but there was one final piece of information we needed. To precisely measure the baryon density, we needed to know where in the sky an FRB came from. If we knew the source galaxy, we would know how far the radio waves traveled. With that and the amount of dispersion they experienced, perhaps we could calculate how much matter they passed through on the way to Earth?
Unfortunately, the telescopes in 2007 weren’t good enough to pinpoint exactly which galaxy – and therefore how far away – an FRB came from.[/quote]
So fast forward to today's technology and instruments ...
[quote]It was 11 years until we were able to place – or localize – our first FRB. In August 2018, our collaborative project called CRAFT began using the Australian Square Kilometre Array Pathfinder (ASKAP) radio telescope in the outback of Western Australia to look for FRBs. … snip …
ASKAP captured its first FRB one month later. Once we knew the precise part of the sky the radio waves came from, we quickly used the Keck telescope in Hawaii to identify which galaxy the FRB came from and how far away that galaxy was. The first FRB we detected came from a galaxy named DES J214425.25–405400.81 that is about 4 billion light-years away from Earth, in case you were wondering.
The technology and technique worked. We had measured the dispersion from an FRB and knew where it came from. But we needed to catch a few more of them in order to attain a statistically significant count of the baryons. So we waited and hoped space would send us some more FRBs.
By mid-July 2019, we had detected five more events, enough to perform the first search for the missing matter. Using the dispersion measures of these six FRBs, we were able to make a rough calculation of how much matter the radio waves passed through before reaching Earth.
We were overcome by both amazement and reassurance the moment we saw the data fall right on the curve predicted by the 5% estimate. We had detected the missing baryons in full, solving this cosmological riddle and putting to rest two decades of searching.[/quote]
In my opinion, this is how science is supposed to work.