By: April Carson
Dark matter theories
The claim that dark matter exists in the Universe was first made by American astrophysicist Fritz Zwicky in the 1930s to explain the mismatch between his measured galactic motion and the expected speed based on the total mass of matter in the cluster discovered with a telescope. The presence of a sufficient amount of previously unknown stuff, known as dark matter, might explain the overly high speeds observed in galaxies.
This idea was confirmed in the 1970s by observations of astronomer Vera Rubin, who timed the rotational speeds of stars on the outskirts of the Andromeda galaxy and discovered that they were near to those found around the center, which again contradicted what was observed. The problem was solved when Zwicky found a great many undetectable matter, which should have been tens of times greater in mass than baryonic matter, and the distance between them.
Role of dark matter
Our work confirms the theory that dark matter is necessary for galaxies, clusters of galaxies, and even entire clusters of galaxies to form. Furthermore, it has been confirmed that without this stuff, galaxies and their clusters would not have had time to develop throughout the course of the Universe's existence.
Because of its role in explaining the movement of galaxies and clusters, the discovery of galaxies that don't contain dark matter was a surprise to experts. The ultradiffuse dwarf galaxies discovered in this study are comprised of stars with a matter density and luminosity ten to a hundred times lower than that of the Milky Way.
Later, the oddness of these galaxies was called into question: it turned out that one of them had been incorrectly measured, resulting in an incorrect estimate of the masses of different sorts of stuff in it, and the second, a nearby massive galaxy could generate dark matter from the first. It appears that these modifications have resolved the mystery of galaxies existing without dark matter.
Galaxy ACG 114905, which has little or no dark matter
In 2021, a research group from the United Kingdom, the Netherlands, and the United States comprised of Pavel E. Mancera Piña of the University of Groningen and ASTRON Institute, as well as other scientists, discovered AGC 114905, a galaxy with little or no dark matter.
This galaxy is located at a distance of 76 ± 5 megaparsecs from the Earth, and it's a disk in which star density decreases as e-r/R as you move away from the center at r, and the typical distance scale R is 1.79 ± 0.04 kiloparsecs.
The total mass of the galaxy is (1.4 ± 0.3) × 10 9 suns. From July to October 2020, the VLA Telescope studied the galaxy for a total of 40 hours. The ultradiffuse dwarf galaxy AGC 114905, like the previous two candidates for galaxies without dark matter, is mostly composed of gas.
Rotation rates of matter in the galaxy
The researchers used the Hubble Space Telescope to examine the galaxy's rotational speeds, and they discovered that dark matter is not required to explain them - there is enough baryonic material concentrated in stars and interstellar gas. If there is dark matter in a galaxy, it does not outweigh baryonic matter by more than ten times, as it does in the majority of galaxies (or at least five). This does not correspond to contemporary cosmological models of galaxy creation.
The researchers think that the long and careful study of AGC 114905, which they performed, rules out the possibility of a significant error in determining its distance. This is precisely why the mistaken conclusion about the lack of dark matter in one of the earlier instances was reached. In addition, there is no sufficiently massive companion nearby AGC 114905 that could take dark matter out of it.
Another alternative to the riddle of a galaxy with an unusually light dark matter mass is the enormous size of the halo, which has a low density. However, this, like the aforementioned low density, does not accord with current theories of galaxy formation. To test this hypothesis, greater distances must be observed for matter in the galaxy's center.
Researchers sometimes utilize one particular hypothesis to explain the lack of dark matter particle sightings in lab experiments. The proposed modifications to General Relativity (GR) attempt to explain the discrepancy between observed galaxy movement speeds and theoretical predictions while maintaining conventional GR equations. It claims that dark matter does not exist, and the contradiction between observable galaxy movement speeds and GR theory is resolved by modifying gravitational law on a galactic scale.
This concept, known as Modified Newtonian Dynamics (MOND), is one of several competing modifications to Albert Einstein's General Theory of Relativity (GTR). The predictions of this theory, however, run counter to AGC 114905's observed characteristics.
Because of the inclusion of the new data, however, they conclude that this error is "too small to be quantified or explained." However, according to their findings, the most likely source of confusion is the incorrect calculation of the galaxy's tilt angle.
Furthermore, five more galaxies without dark matter were recently discovered, with a different inclination to the line of sight from the Earth. Astrophysicists believe that more astronomical observations are required to prove the lack of dark matter in certain ultradiffuse dwarf galaxies.
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About the Blogger:
April Carson is the daughter of Billy Carson. She received her bachelor's degree in Social Sciences from Jacksonville University, where she was also on the Women's Basketball team. She now has a successful clothing company that specializes in organic baby clothes and other items. Take a look at their most popular fall fashions on bossbabymav.com
To read more of April's blogs, check out her website! She publishes new blogs on a daily basis, including the most helpful mommy advice and baby care tips! Follow on IG @bossbabymav
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