Missing mass (split from Dark Matter)

[SergUpstart]

29 minutes ago, Markus Hanke said:

3. A modification of the laws of gravity. The idea here is that in actual fact there is no DM, but that gravity on larger scales is not well described by the GR field equations, requiring some amended (scale-dependent?) law of gravity on those scales. The appearance of DM is then simply the difference between what GR predicts, and what the actual motion of test particles under the amended gravity law is like.

In astronomy, the problem of hidden mass has often arisen. For example, at the beginning of the 19th century, an anomaly was discovered in the motion of the planet Uranus and the question arose whether Newton's law of gravity is correct or there is still a planet in the solar system. This question was resolved in 1846 by the discovery of the planet Neptune. Then an anomaly in the movement of Mercury was discovered, and astronomers began to look for another planet between Mercury and the Sun. She was even given the name Vulcan. But in 1915, Einstein explained the anomaly in the motion of Mercury from the perspective of a new theory of gravity, and the search for the Volcano stopped.

 

In the mid-20th century, this question arose again with the discovery of anomalies in the orbital velocities of stars in galaxies. I believe that this time the question will not be solved unambiguously by detecting the hidden mass or changing the law of gravity, but both will be needed.

[SergUpstart]

Along with the search for and explanation of dark energy and dark matter, astronomers are faced with a third task: to find the missing "normal" (or as it is also called baryonic) matter of the Universe, writes IFLS.

https://www.iflscience.com/space/a-little-of-the-universes-missing-matter-has-just-been-found-close-to-home/

The scientists ' innovative approach found that a tiny fraction of the missing matter lurks close enough (by astronomical standards) to the Solar System, suggesting that such zones are quite common.

Unlike dark matter and dark energy, the missing matter must be a normal gas and possibly a small amount of dust, like the universe we can see.

"The problem is that when we look back at the early universe, we can measure the amount of matter that was then present in it, but in more recent observations, half of it has disappeared," the study authors write.

Even if we allow the transformation of matter into the energy of stars, the most visible matter will not be so much. Over the past few years, astronomers have made considerable progress in finding this missing matter, for example, they found most of it in diffuse gas between galaxies hundreds of millions of light-years away. However, this is still not enough.

Yuanming Wang, a PhD candidate at the University of Sydney's School of Physics, has developed a rather unusual method to help find the missing matter. She used her technique to determine a hitherto undetected stream of cold gas in the Milky Way about 10 light-years from Earth.

"This gas is impossible to detect using traditional methods, as it does not emit its own visible light and is simply too cold to detect using radio astronomy," Wang said.

She found it when she was looking at the twinkling galaxies. Astronomers have long known that some galaxies flicker when observed with radio telescopes.

 

[beecee]

1 hour ago, SergUpstart said:

Along with the search for and explanation of dark energy and dark matter, astronomers are faced with a third task: to find the missing "normal" (or as it is also called baryonic) matter of the Universe, writes IFLS.

https://www.iflscience.com/space/a-little-of-the-universes-missing-matter-has-just-been-found-close-to-home/

The scientists ' innovative approach found that a tiny fraction of the missing matter lurks close enough (by astronomical standards) to the Solar System, suggesting that such zones are quite common.

Unlike dark matter and dark energy, the missing matter must be a normal gas and possibly a small amount of dust, like the universe we can see.

"The problem is that when we look back at the early universe, we can measure the amount of matter that was then present in it, but in more recent observations, half of it has disappeared," the study authors write.

Even if we allow the transformation of matter into the energy of stars, the most visible matter will not be so much. Over the past few years, astronomers have made considerable progress in finding this missing matter, for example, they found most of it in diffuse gas between galaxies hundreds of millions of light-years away. However, this is still not enough.

Yuanming Wang, a PhD candidate at the University of Sydney's School of Physics, has developed a rather unusual method to help find the missing matter. She used her technique to determine a hitherto undetected stream of cold gas in the Milky Way about 10 light-years from Earth.

"This gas is impossible to detect using traditional methods, as it does not emit its own visible light and is simply too cold to detect using radio astronomy," Wang said.

She found it when she was looking at the twinkling galaxies. Astronomers have long known that some galaxies flicker when observed with radio telescopes.

 

https://www.csiro.au/en/News/News-releases/2020/Cosmic-bursts-unveil-missing-matter

Cosmic bursts unveil Universe’s missing matter: 20th May 2020

The researchers have now found all of the missing 'normal' matter in the vast space between stars and galaxies, as detailed today in the journal Nature  .

 

extract:

 

"Intergalactic space is very sparse," he said. "The missing matter was equivalent to only one or two atoms in a room the size of an average office."

"So it was very hard to detect this matter using traditional techniques and telescopes."