New Study Says Space Science Was Wrong in Understanding Dark Matter

Rodiano Bonacci
Settembre 13, 2020

So, objects on the far side of that gravitational field, such as distant galaxies, appear to us magnified, smeared, duplicated, and distorted. And models of the early universe create galaxies and clusters of galaxies by building structures formed by dark matter. The characteristic of the cosmic microwave background can be explained by the presence of dark matter. So, dark matter remains as elusive as the Cheshire Cat in Alice in Wonderland - where you see only her smile (in the form of gravity) but not the animal itself. The fact that this model gets the big picture so right was their favor.

But a new study shows that the same models get the details wrong - with a full-scale sequence.

(Nanowerk News) Astronomers have discovered that there may be a missing ingredient in our cosmic recipe of how dark matter behaves.

The new study, performed by an global team of researchers, took advantage of a phenomenon called gravitational lensing.

This effect in space that results from a star or even a galaxy curving space and thus bending the path of light as it passes the object. A lovely example of this is an Einstein ring, where a single object appears multiple times forming a ring-like arrangement.

One of the ways astronomers can detect dark matter is by measuring how its gravitational pulls distort space, an effect called gravitational lensing. What they found could change current numerical models of the universe entirely.

The researchers used gravity lensing to set up an experiment that was at least theoretically very simple. We created a model of the early universe showing how dark matter helped structure the first galaxies and attract them into the cluster. These models, as they move forward, provide an explanation of how the distribution of that dark object should have been at different points in the history of the Universe up to the present.

According to these models, the Universe was built hierarchically.

Because a higher concentration of dark matter in a cluster gives a more dramatic light-bending effect, the team surmised that the presence of the nested lenses were being produced by the gravity of dense pockets of dark matter inside the individual cluster galaxies that had magnified and warped the passing light. The extra gravitational force at the points where the fibers intersect will be drawn in the regular case, which will lead to the first galaxies. Using this map, scientists traced lensing distortions by examining how matter distorts light and mapping dark matter in clusters with high accuracy. Not only are they closely related to each other by the gravitational pull of dark matter, the individual cluster galaxies themselves are also filled with dark matter. By measuring lens distortions, astronomers can track the amount and distribution of dark matter.

Meanwhile, in the real universe...

...

Hubble's crisp images were taken by the telescope's Wide Field Camera 3 and Advanced Camera for Surveys. Follow-up imaging, using a very large telescope, helped to identify the distances of those objects based on how much their light was transferred to the red edge of the spectrum by the expansion of the universe - the larger redshift, and the more distant the object.

The reference: "An excess of micro-gravitational lenses observed in galaxy clusters" by Massimo Mingetti, Guido Davoli, Pietro Bergamini, Piero Rosati, Priamvada Natarajan, Carlo Giocoli, and Gabriel B. Kamenya, R., Francesco Calura, Claudio Grillo, Amata Mercurio and Eros Vanzella, 11 September 2020, Science.

When the team sat down to analyse the data, they found the large-scale lensing effects as expected to be produced by the galaxy as a whole. The researchers found a strong agreement between the lenses' appearance of objects and the location of individual galaxies, which allowed them to verify their mass-distribution calculations.

For now, however, there are already likely to be teams with additional data in hand that could perform similar analysis, so we'll have to wait for those to be done. They did so to identify possible lens locations and where they could create the greatest distortion.

The two do not match. Areas that make up more distortion in the real-universe galaxy were significantly larger than those in the model.

Dark matter is the invisible glue that keeps stars bound together inside a galaxy.

This isn't the first discrepancy of the sort we've seen. Normal matter, the stuff we can find, only accounts for about five percent of the larger cosmos, so the theory goes. But even the slightest hold we do possess might be missing a significant thing. So it seems that both problems require adjustment in opposite directions, rather than finding two problems that can be solved by one adjustment.

Research published this week revealed an unexpected discrepancy between observations of dark matter concentrations in three massive clusters of galaxies encompassing trillions of stars and theoretical computer simulations of how dark matter should be distributed. Since both of those get the big picture of the Universe largely right, however, the issue is going to be a subtle one and consequently hard to identify, should these results get an independent confirmation.

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