New data from the Hubble Space Telescope unveils much higher concentrations of dark matter than previously believed in some galaxies, by over an order of magnitude.
It would be, let’s say, very optimistic to claim that we have a good handle on the dark matter situation. But even the slightest hold we do possess might be missing a significant thing.
The recently found concentrations intrigue scientists, and they might need some extra work to figure everything out. Thanks to Hubble, we might be closer to the truth than we might know. Here is what you need to know.
A Hubble Discovery That Matters Too Much
The concentrations discovered are incompatible with theoretical models, indicating a huge gap in our understanding – the models could be wrong, or there could be a dark matter property we don’t understand completely. Or at least, that’s what a research team thinks.
Discussing possible origins for this difference, astrophysicist Massimo Meneghetti of the National Institute for Astrophysics in Italy, offered few details. He stated: “One possible origin for this discrepancy is that we may be missing some key physics in the simulations.”
A way to indirectly “see” dark matter is via gravitational lensing. Massive objects, such as clusters of galaxies, produce an intense gravitational field that spacetime bends – it means that any light reaching that area moves on a curving path. So, objects on the far side of that field, like distant galaxies, seem to us magnifies, duplicated, and distorted.
Studying those twists and putting the galaxies back together, researchers can find how the light was distorted. And they can also map the gravitational field – the bigger the twist, the stronger the gravitational field and subtract the visible matter to obtain a map of the dark matter.
Such a thing is what Meneghetti and his team were doing. They observed 11 galaxy clusters utilizing the Hubble Space Telescope and the European Southern Observatory’s Very Large Telescope.
The Team’s Findings
The team discovered large-scale lensing effects as expected to be made by the galaxy as a whole. But, what it found next, it’s more intriguing.
Researchers spotted some small lenses, generated by individual galaxies within the clusters. Such things didn’t appear in simulations of the clusters, indicating an excess of dark matter.
Meneghetti added: “[the galaxy clusters] are ideal laboratories to understand if computer simulations of the Universe can reliably reproduce what we can infer about dark matter […].”
The team’s final results include a much greater dark matter concentration in those individual galaxies than the models allowed. The models, however, were based on the researcher’s best understanding of dark matter.
More work is still needed to find where the additional mass comes from.
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