Properties of galaxies reveal the invisible hand of dark matter

Astronomical computer simulations point to strong evidence that dark matter exists, supported by observations of features in galaxies that are hard to explain without it

Computer simulations made by astronomers, including those at the University of California at Irvine, support the existence of dark matter. Although dark matter has not been directly detected, many scientists believe it must exist to explain various phenomena in the observable universe.
Computer simulations made by astronomers, including those at the University of California at Irvine, support the existence of dark matter. Although dark matter has not been directly detected, many scientists believe it must exist to explain various phenomena in the observable universe.

Computer simulations made by astronomers, including those at the University of California at Irvine, support the existence of dark matter. Although dark matter has not been directly detected, many scientists believe it must exist to explain various phenomena in the observable universe.

The article refers to a fundamental debate in astrophysics - does dark matter have to exist to explain how the universe works the way it does, or can physicists only explain how things work based on the matter we can directly observe? Today, many physicists think that something like dark matter must exist to explain the motion of stars and galaxies.

"Our paper shows how we can use real observed relationships as a basis for examining two different models to describe the universe," said Francisco Mercado, lead author. "We propose a robust test to differentiate between the two models."

The test involved running computer simulations with both types of matter - normal and dark - to explain the presence of intriguing properties measured in real galaxies. The team reported their results in the Monthly Notices of the Royal Astronomy Society.

The features in the galaxies the team found "are expected to appear in a universe with dark matter but would be difficult to explain in a universe without dark matter," Mercado said. "We show that these features appear in observations of many real galaxies. If we take these data simply, they reaffirm the position of the dark matter model as the model that best describes the universe we live in."

These features that Mercado noted describe patterns in the motions of stars and gas in galaxies that appear to be possible only in a universe with dark matter.

"Observed galaxies seem to obey a tight connection between the matter we see and the inferred dark matter we detect, so much so that some have suggested that what we call dark matter is actually proof that our theory of gravity is wrong," said co-author James Bullock. "We showed that not only does dark matter predict the connection, in many galaxies it can also explain what we see more naturally than modified gravity. I am even more convinced that dark matter is the right model."

The features also appear in observations made by followers of a universe without dark matter. "The observations we tested—the very observations where we found these features—were made by proponents of theories without dark matter," said co-author Jorge Moreno. "Despite their obvious presence, the community has analyzed these properties very little, if at all. To start the conversation, people like us, scientists who work with both normal matter and dark matter, were needed."

"As stars are born and die, they explode into supernovae, which can shape the centers of galaxies, naturally explaining the existence of these features," Moreno said. "Simply, the properties we tested in the observations require both the existence of dark matter and the inclusion of the physics of normal matter."

Now that the dark matter model of the universe seems to be leading, the next step is to see if it will remain consistent in a dark matter universe.

"It will be interesting to see if we can use the same relationship to differentiate even between different models of dark matter," Mercado said. "Understanding how this relationship changes in different dark matter models could help us constrain the properties of dark matter itself."

for the scientific article

More of the topic in Hayadan: (Beresheet is the Hebrew name for the book of Genesis)

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