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Astronomers seem to have revealed a puzzling detail in the way dark matter behaves.
They found small, dense concentrations of dark matter that bend and magnify light much
more strongly than expected.
Dark matter is a mysterious, invisible substance that makes up the bulk of a galaxy. The gravitational
pull exerted by dark matter is thought to tie galaxies together throughout the universe.
There is so much regular matter and dark matter concentrated in massive galaxy clusters that
their gravity magnifies and warps light from distant background objects.
We call this effect “gravitational lensing.” We can map where the dark matter is in galaxy
clusters by observing how the light bends.
Gravitational lensing distorts the appearance of background galaxies into deformed shapes
and elongated arcs. Pictures of lensing galaxy clusters are filled with the smeared images
of remote background galaxies.
The higher the concentration of dark matter in a galaxy cluster, the more dramatic its
light-bending power is. Smaller clumps of dark matter associated with individual galaxies
in the galaxy cluster create more distortions. In some sense, the galaxy cluster acts as
a large lens that has many smaller lenses embedded inside of it.
But strangely, astronomers found that three galaxy clusters used in their study had concentrations
of dark matter that are so massive that the lensing effects they produce are 10 times
stronger than originally expected.
Hubble’s crisp images, coupled with observations from the very large telescope in Chile, helped
astronomers produce a more accurate dark-matter map.
By measuring the lensing distortions, astronomers could trace out the amount and distribution
of dark matter.
This recent study could signal a gap in our current understanding of the nature of dark
matter and its properties. It shows us that there’s clearly a missing feature of the
real universe that we simply are not capturing in our current theoretical models.
With studies like this, astronomers look forward to continuing to pin down the intriguing nature
of dark matter to better understand the secrets of our mysterious universe.
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