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The puzzle of the strange galaxy made of 99.9% dark matter is solved
phys.org ^ | October 13, 2020 | by Instituto de Astrofísica de Canarias

Posted on 10/13/2020 12:45:50 PM PDT by Red Badger

Image and amplification (in color) of the ultra-diffuse galaxy Dragonfly 44 taken with the Hubble space telescope. Credit: Teymoor Saifollahi and NASA/HST.

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At present, the formation of galaxies is difficult to understand without the presence of a ubiquitous, but mysterious component, termed dark matter. Astronomers have measure how much dark matter there is around galaxies, and have found that it varies between 10 and 300 times the quantity of visible matter. However, a few years ago, the discovery of a very diffuse object, named Dragonfly 44, changed this view. It was found that this galaxy has 10,000 times more dark matter than the stars. Taken back by this finding, astronomers have made efforts to see whether this object is really anomalous, or whether something went wrong in the analysis of the observations. Now we have the answer.

An international team led by the Kapteyn Institute of the University of Groningen (the Netherlands), with participation by the Instituto de Astrofísica de Canarias (IAC) and the University of La Laguna (ULL), has found that the total number of globular clusters around Dragonfly 44 and, therefore, the dark matter content, is much less than earlier findings had suggested, which shows that this galaxy is neither unique nor anomalous. The result was recently published in Monthly Notices of the Royal Astronomical Society (MNRAS).

The galaxy Dragonfly 44 was discovered in a deep survey of the Coma cluster, a cluster with several thousand galaxies. From the start, the galaxy was considered remarkable by the researchers because the quantity of dark matter they inferred was almost as much as that in the Milky Way, the equivalent of a billion solar masses.

However, instead of containing around a hundred thousand million stars, as has the Milky Way, DF44 has only a hundred million stars, a thousand times fewer. This means that the amount of dark matter was ten thousand times greater than that of its stars. If this had been true, it would have been a unique object, with almost 100 times as much dark matter as that expected from the number of its stars.

Nevertheless, by an exhaustive analysis of the system of globular cluster around Dragonfly 44, the researchers have detected that the total number of globular clusters is only 20, and that the total quantity of dark matter is around 300 times that of the luminous matter, which means that it is not way outside the normal value for this type of galaxies.

"The fact that in our work we found only 20 globular clusters, compared with the 80 previously claimed, reduces drastically the amount of dark matter which the galaxy is believed to contain," explains Ignacio Trujillo, an IAC researcher and a co-author of the article. "Moreover, with the number of globular clusters we found, the amount of dark matter in Dragonfly 44 is in agreement with what is expected for this type of galaxies. The ratio of visible to dark matter is no longer 1 in 10,000 but one in 300," adds Trujillo.

"Dragonfly 44 has been an anomaly all these years that could not be explained with the existing galaxy formation models. Now we know that the previous results were wrong and that DF44 is not extraordinary. It is time to move on," points out Teymoor Saifollahi, researcher at the Kapteyn Institute and the first author of the article.

"Our work shows that this galaxy is not so singular nor unexpected. That way the models of galaxy formation can explain it without the need for modification," says Michael A. Beasley, another IAC researcher, specialist in globular clusters, and a co-author of the article.

The total number of globular clusters is related to the total mass of a galaxy. So, if the number of globular clusters is measured, the quantity of dark matter can be found, especially if the quantity of visible matter is only a small fraction of the total.

"However, we don't have a physical explanation for this relation between the total number of globular clusters and the total mass of the galaxy. This is purely observational knowledge. It could be that it has to do with the quantity of the original gas from which the stars, and the globular clusters themselves, have formed. The more dark matter there is in a galaxy, the more gas it contains," suggests Johan H. Knapen, an IAC researcher and also a co-author of the article.

Explore further The dark side of the diffuse galaxies:

https://phys.org/news/2016-05-dark-side-diffuse-galaxies.html

More information: Teymoor Saifollahi et al, The number of globular clusters around the iconic UDG DF44 is as expected for dwarf galaxies, Monthly Notices of the Royal Astronomical Society (2020). DOI: 10.1093/mnras/staa3016 Journal information: Monthly Notices of the Royal Astronomical Society

Provided by Instituto de Astrofísica de Canarias

https://phys.org/journals/monthly-notices-of-the-royal-astronomical-society/


TOPICS: Astronomy; Education; History; Science
KEYWORDS: astronomy; darkenergy; darkforce; darkmatter; dragonfly44; galaxy; science; speedofdark
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To: Red Badger

How do they know something exists that can’t be measured, observed, or tested?


21 posted on 10/13/2020 2:51:25 PM PDT by Blood of Tyrants (Where do you find the word "except" in the 2nd Amendment?)
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To: Blood of Tyrants
It can be observed. You certainly cannot identify position and direction/momentum at the same time. You can approximate one or the other. The particle can be in several different probable places at the same time. To try to identify its superposition causes it to "collapse". Quantum mechanics is sort of like that kind of woman that drives you nuts if you pay any attention to her. It's best left to the experts.
22 posted on 10/13/2020 3:14:46 PM PDT by BipolarBob (Rome wasn't built in a day. All Hail the night shift!)
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To: Olog-hai

Just think...if you could eliminate the empty space between the nucleus and electrons then there would be no fat people.


23 posted on 10/13/2020 3:30:03 PM PDT by MtnClimber (For photos of Colorado scenery and wildlife, click on my screen name for my FR home page.)
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To: Red Badger

It sounds like dark matter is just a fudge factor.


24 posted on 10/13/2020 4:16:10 PM PDT by The Duke (President Trump = America's Last, Best Chanca)
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To: The Duke

Isn’t dark matter just like Hillary’s emails? You can’t see them, can’t find them, but there out there somewhere.


25 posted on 10/13/2020 4:38:07 PM PDT by TheGreatFazool (The Great Fazool)
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To: The Duke

Isn’t dark matter just like Hillary’s emails? You can’t see them, can’t find them, but they’re out there somewhere.


26 posted on 10/13/2020 4:38:37 PM PDT by TheGreatFazool (The Great Fazool)
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To: BipolarBob

Dark comedy?


27 posted on 10/13/2020 4:49:35 PM PDT by Getready (Wisdom is more valuable than gold and diamonds, and harder to find.)
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To: BipolarBob

It is inferred...not observed. One presupposes those cosmic structures hsve been out there so long...some undetectable force MUST be holdimg them together. There is not enuf visible or observable matter to do the trick. No thing we can observe solves the problem. Viola...it must be dark matter by elimination of all other possibilities. Maybe our assumptions are incorrect??


28 posted on 10/13/2020 4:56:57 PM PDT by Getready (Wisdom is more valuable than gold and diamonds, and harder to find.)
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To: Red Badger

Matter is something...Dark matter is nothing...Nothingness...It’s the empty spaces between matter...


29 posted on 10/13/2020 4:57:44 PM PDT by Iscool
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To: Red Badger

Neutrinos don’t have much mass but the Universe makes them in gigantic quantities. As the Universe has expanded it has stretched out the background radiation all the way to radio waves. It has also slowed down a bunch of neutrinos that use to travel near light speed, enough so that they now orbit galaxies as dark matter.


30 posted on 10/13/2020 6:08:55 PM PDT by Nateman (If the left is not screaming, you are doing it wrong!)
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To: MtnClimber

Wouldn’t even be two-dimensional people either.


31 posted on 10/13/2020 6:57:31 PM PDT by Olog-hai ("No Republican, no matter how liberal, is going to woo a Democratic vote." -- Ronald Reagan, 1960)
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To: Olog-hai; All

>the empty space between the nucleus and electron shells of atoms...

A question. If the speed of light in a vacuum is a constant and and a vacuum is a space devoid of matter, “space” is not perfect and even the deepest interstellar void has a density of an atom per cubic whatever (meter, light year, etc).

At the atomic scale a photon traveling through a semi-transparent substance is in a “space devoid of matter”, yet the speed of the photon is less than c as given by the refractive index of the material it is passing through.

Looks to me that there is something I’m missing here.

There’s another question that has me a bit confused. If a “big-bang” is a given, (not quite sure how or if Plank Space or the Vacuum Energy field (whatever that is) could have been around BEFORE the Universe popped into existence), matter and energy being interchangeable, the sum total of each at any point in time during the existence of the Universe would be the same. A Universe a picosecond old would be really really hot and dense but also very very small, an elderly Universe tens or hundreds of billion years old would be way way colder and less dense as well as being Hugh (and series) but both would have exactly the same total amount of matter and energy.

The one thing that I have never seen factored in to the question of the missing mass is weather the massive quantity of kinetic energy from all the “Stuff” moving through space, some portion of it moving at some percentage of C, thus increasing it’s mass the closer to c it gets, might negate the need for “dark matter”

Am I all wet or perhaps just covered in quantum foam?


32 posted on 10/14/2020 2:52:03 AM PDT by ADemocratNoMore (The Fourth Estate is now the Fifth Column)
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To: blueunicorn6

If that galaxy is 99.99% Dark matter, why can we see it?...................


33 posted on 10/14/2020 5:05:46 AM PDT by Red Badger (Sine Q-Anon.....................very............)
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To: jimmygrace

AND it comes out FAST AND FURIOUS!.......................


34 posted on 10/14/2020 5:11:20 AM PDT by Red Badger (Sine Q-Anon.....................very............)
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To: Blood of Tyrants

35 posted on 10/14/2020 5:21:31 AM PDT by Red Badger (Sine Q-Anon.....................very............)
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To: Nateman

Klaatu- Little Neutrino:

https://www.youtube.com/watch?v=yk0Is8-gGSQ


36 posted on 10/14/2020 5:35:30 AM PDT by Red Badger (Sine Q-Anon.....................very............)
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To: Iscool

Space is absence of Matter.

Matter is absence of Space........................


37 posted on 10/14/2020 5:36:44 AM PDT by Red Badger (Sine Q-Anon.....................very............)
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To: The Duke

38 posted on 10/14/2020 5:41:14 AM PDT by Red Badger (Sine Q-Anon.....................very............)
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