Missing Half of Normal Matter in the Universe Has Been Detected

Baryons are neutrons and protons (or matter that has mass). Just looking into the night sky and seeing all the stars and galaxies, and yes, including black holes, white dwarfs, brown gas giants, etc., still only accounts for 10% of the universe.

What about the other 90%?

That is where cosmology comes in to play. There are concepts and ideas you need to know.

Big Bang – The idea that the entire universe, when placed on a backward time-line, as if it was a movie playing in reverse, was an infinitely small, singularity. Space and time did not exist. Then, it all blew up into a hot mess that needed room to expand into. The idea is that there was a “great expansion” allowing room for all the electromagnetic radiation (that was all there was) to expand into and cool down enough to become particles is still debated over by various cosmologists.

Cosmic Microwave Background (Radiation) – Usually referred to CMB (the radiation part is inferred), this what all that hot particle soup from the Big Bang cooled down to. The lovely temperature of 3 K (2.725 to be precise). This was finally measured by satellite in the 1990s by the COBE mission.

Galaxy – A cluster of stars held together by gravitation. Typically, like the Milky Way, a massive or supermassive black hole at the center. Our galaxy is a lovely spiral but there are other types.

Dark Matter – This is a fun one! Some argue that it is not baryons while others use the term as “matter that is not detected”. They both agree that DM is affected by gravity. There are times when you need to be specific and say “non-baryon”. Wikipedia.

Now we can put it all together!

Scientists have computer models of galaxy formations. The more we observe the better the models reflect the observations. One of the better models have what are called “filaments” between galaxy pairs. These filaments are baryon filled but due to their sparseness they are not visible.

In the following news story, two different teams paired up galaxies and CMB readings between them. One group did 600,000 pairs while the other went over a million.

There’s no sweet spot – no sweet instrument that we’ve invented yet that can directly observe this gas,” says Richard Ellis at University College London. “It’s been purely speculation until now.” Because it's not quite hot enough for X-ray telescopes to observe.

Both teams took advantage of a phenomenon called the Sunyaev-Zel’dovich effect that occurs when light left over from the big bang passes through hot gas to find another way to definitively show that these threads of gas are really there. As photons of light travel, some of them scatters off the electrons in the gas, leaving a dim patch in the cosmic microwave background from the birth of the cosmos that were to faint to be mapped by the Planck satellite in 2015.

Both teams selected pairs of galaxies from the Sloan Digital Sky Survey that were expected to be connected by a strand of baryons. They stacked the Planck signals for the areas between the galaxies, making the individually faint strands detectable en masse.

Observations of galaxies and galaxy clusters in the local universe can account for only 10% of the baryon content -made of particles called baryons rather than dark matter- inferred from measurements of the cosmic microwave background and from nuclear reactions in the early Universe. Locating the remaining 90% of baryons has been one of the major challenges in modern cosmology. The missing links between galaxies have finally been found. This is the first detection of the roughly half of the normal matter in our universe – protons, neutrons and electrons – unaccounted for by previous observations of stars, galaxies and other bright objects in space.

DailyGalaxy.com, Oct. 9, 2017 – "Everybody Knew It Had To Be There" --Missing Half of Normal Matter in the Universe Has Been Detected.

To those that say it is a waste of money look at what has been accomplished. By using the Sloan Digital Sky Survey, the Plank satellite, the CMB observations, and computer modeling, something we did not know before has been demonstrated!

Still in peer review at the arXiv, the paper is awaiting publication.

Cool. Science is cool!

very cool.
i wish i wasnt so stupid so i could understand this stuff better.

something i heard a long time ago and still baffled me

the big bang was not an explosion IN space. it was an explosion OF space.

trippy #

Very cool! And very well done thread TEO
You did an excellent job presenting the info.

a reply to: TEOTWAWKIAIFF

Those guys are really, really smart. Came up with a hypothesis and demonstrated it to be valid.

Lots of atoms between galaxies. Awesome.

Now, what the hell is dark matter and how can it be found?

a reply to: TinySickTears

You'e got the gist of it! The part that is difficult is the article says, "half" which is 50%. The other percentage is 90%.

If I read it correctly, 45% of matter (not dark matter) has been detected and confirmed by another team, as existing between galaxies in strings of particles.

This is a big answer to many questions. But you know, so is kicking it on a warm summer night looking up at the vastness of it all!

a reply to: zosimov

Thanks!

Explaining things is one method of learning. For a more precise definition please see other sources! I just like the "it was right there the whole time" nature of this one!

Even their headline stated it: "Everybody knew it had to be there"

So does non-baryon dark matter even exist? Like if they keep looking and go from 90% to 100% of matter accounted for...

a reply to: Phage

That is question. If we can't detect *these filaments* with our x-ray telescopes what about real dark matter?

My best guess would be another indirect measurement but this time with gravity (somehow). Maybe the LHC can shed some light on how to directly observe dark matter.

One team getting a significant sigma of measurement would be cool news. But two? Yup, real smart people thought this up!

That is a noodle bender. How in the vastness of space do you measure something you can't detect?

a reply to: TEOTWAWKIAIFF

How in the vastness of space do you measure something you can't detect?

I give up. How?

The gravitational effects are measured though.

a reply to: TEOTWAWKIAIFF

Excellent post but I have one tiny (in fact subatomic) bone to pick. Baryons not only include the nucleons (protons and neutrons) but all tri-quark particles, which would also include hyperons like the lambda zero particle, or the omega minus particle. Hyperons are strange little things, and that was a play on words. To get it read The Eightfold Way by Murray Gell Mann and Yuval Neʾeman.

a reply to: FocusedWolf

I think it is the other way round. 10% of visible matter accounted for by galaxies and observation. That left 90% as "dark matter". This news announcement cuts that amount in half now.

There is only 45% unaccounted for. The "how to see un-seeable matter?" is a great question.

a reply to: F4guy

And the new Omega Chi one as well.

I did enough to explain the article!

And now everybody knows! lol. I'm an armchair scientist, especially space! I know enough to be dangerous with the terms! Except computer science and discrete math where I know even more than enough to be dangerouser!

ATS... Disclaimer: For a more proper source than the ramblings of TEOT, please see "subject matter experts" and those working in the field.

We're all in this together!

a reply to: TEOTWAWKIAIFF

The estimated gas density in these 15 Megaparsec-long filaments is approximately 6 times the mean universal baryon density, and overall this can account for ∼30% of the total baryon content of the Universe. This result establishes the presence of ionised gas in large-scale filaments, and suggests that the missing baryons problem may be resolved via observations of the cosmic web.

Cosmic web. Gotta love it.

It sounds like the remaining normal matter is expected to be found with more observation, now that they know where to look.
arxiv.org...

a reply to: Phage

Because WIMPs are so "weakly interacting" — that is, they cannot interact with normal matter via the electromagnetic, strong or weak forces — XENON1T can detect them only by looking out for lucky collisions between WIMPs and atoms in a chamber filled with pure liquid xenon cooled to minus 139 degrees Fahrenheit (minus 95 degrees Celsius).

space.com - The World's Most Sensitive Dark Matter Detector Is Now Up and Running.

There is this thing! I thought there was another one as well somewhere else in Europe that was doing the same type of experiment. This one is in Italy. The other? I don't recall. Germany? Gah. There are probably several but those are the ones I remember.

Yeah, the gravity interaction has been measured (sorry, didn't mean that it hasn't) which is why we have an estimate on what is out there. But I'm not sure how to detect it.

Do you know of a way? I've given my best guess but a rather pathetic attempt.

a reply to: TEOTWAWKIAIFF

I couldn't even figure out how to find that normal stuff.

a reply to: Phage

That's cosmology for you!

I love thinking about things unthinkable. Like the cosmic web (how groovy!) means galaxies are connected to each other. Like neurons in the brain.

Hey TinySickTears, I'll join you on the couch sipping a beer and pondering how trippy this stuff is!

Maybe we need a ghost detector (he says half jokingly)!

are we still open to my electric universe cause i gotta tell ya.....Tesla leaned that way

electric universe doesn't need D M.....

a reply to: GBP/JPY

Wouldn't discovering more matter mean the opposite of an electric universe?

I'm really asking because I looked at the EU (ha!) before and moved on.

If there is free flowing electricity around, it would follow the filaments between galaxy pairs and be even more brain like! Especially if galaxies "talk" to each other.

If a galaxy collides with one another in the EU what happens? If they were similar charged, wouldn't they repel each other?

You can have your EU theory! Until this paper, 90% of matter was considered "not there" and now look!

It's all good.

originally posted by: TEOTWAWKIAIFF
Baryons are neutrons and protons (or matter that has mass). Just looking into the night sky and seeing all the stars and galaxies, and yes, including black holes, white dwarfs, brown gas giants, etc., still only accounts for 10% of the universe.

What about the other 90%?

My understanding is quite different from this. I thought the baryons we observed locally accounted for 2.5% of the mass energy content in the corresponding region of space, and that the estimated baryonic content was 5% of the mass energy content the same region. This 10% figure as I understand it applies to a much larger scale and implies that of the 5% of the universe which is baryonic, that only 10% of that or 0.5% is (or was) observable. This is lower than the 2.5% seen locally because most of the universe is much further away. So I think what they claim to have found is some of the gap between the 0.5% baryonic mass energy content previously observed and the 5% of the baryonic mass energy content believed to exist.

See this similar article from December 2005 which talks about finding more baryonic matter locally and talks about some of the figures I'm citing.

Universe's missing mass found in the cosmic web

Observations of the afterglow of the Big Bang known as the cosmic microwave background (CMB) suggest that protons, neutrons and other (three-quark) baryon particles only account for about 5% of the universe's energy density – the rest is believed to consist of enigmatic dark matter and dark energy. However, the combined mass of all of the stars within a radius of about a billion light-years from Earth only amounts to about 2.5% of the energy density within that region. Computer simulations predict that the missing baryons instead exist within low-density plasma filaments millions of light-years long.

Your OP implies maybe this has something to do with dark matter but I'm not clear on that and I'm not clear that it really does, but it seems like it's just about missing baryonic matter though if anybody has a better understanding it's welcome.

The paper Anna de Graaff et al cited for their 10% figure spells out that dark matter is something else, if I'm reading it correctly:

The baryon content of the Universe

First, let us note that the baryon mass-to-light ratio corresponds to the mass-to-light ratio of stars, and not to the dynamical one which usually includes dark matter (DM). In fact, the presence of DM in the internal parts of spiral galaxies is very evident (Persic & Salucci 1991), so we cannot ignore its contribution to the mass of a galaxy.

So does non-baryon dark matter even exist? Like if they keep looking and go from 90% to 100% of matter accounted for..

a reply to: FocusedWolf

You misunderstand what was found. Which is understandable because it took me a minute to figure it out too.

The majority (perhaps even consensus) view in Cosmology is that the mass of the Universe is about 68% Dark Energy, 27% Dark Matter, and 5% 'Regular' Matter/energy. (Exact numbers differ according to calculation assumptions, but 'Regular' Matter is between 5% and 10% of the total mass of the universe).

Until now we have been able to account for only half of that 5% - or only 2.5% of the total mass of the universe. The new study appears to have 'found' the other 2.5%.

We still don't know what exactly Dark Matter is, though we can absolutely detect its gravitational effects.

We still don't know what exactly Dark Energy is (or even if it is something that actually corresponds to what we experience as 'energy'), though we are making progress on figuring out what its properties would need to be and therefore what we might be looking for. Dark Energy is measured in mass because, you know, E = MC^2 and all that Einstein business.

Missing Half of Normal Matter in the Universe Has Been Detected

My wife finally came out of the can?