Our understanding of dark matter just became even more warped — literally
Our understanding of dark matter just became even more warped — literally.
Two eyes are better than one
Because astronomers are unable to see dark matter directly, they study ordinary matter around a target, measuring how it is affected by the invisible source of gravity.
One method ofmeasuring dark matteris studying the way light from distant clusters of galaxies bends as it travels past a clump of dark matter. This effect, known as gravitational lensing, can magnify, or even make multiple images from, distant objects.
Astronomers recently examined 11 distant galaxy clusters, using theHubble Space Telescopeand the Very Large Telescope (VLT) in Chile. These groups of galaxies are rich with dark matter both within the galaxies (small-scale clumps) and joining the clusters together (large-scale clumps).
Razor-sharp images from Hubble, combined with advanced spectral analysis from the VLT provided astronomers with the tools they needed to probe these distant galactic clusters. These observations revealed dozens of background targets with their light paths bent bydark matter. By studying these targets, researchers were able to map out the amount and placement of pockets of invisible dark matter.
Examination of this data revealed gravitational lensing from small-scale dark matter clumps is 10 times greater than expected.
“To me personally, detecting a gnawing gap — a factor of 10 discrepancy in this case — between an observation and theoretical prediction is very exciting… It’s these kinds of gaps and anomalies that have often revealed that either we were missing something in the current theory, or it points the way to abrand-new model,” saidPriyamvada Natarajan, astrophysicist at Yale University.
Researchers also found images of different sizes nestled inside one another like Russian Matryoshka dolls. This new study could show a gap in astronomers’ understanding of dark matter.
“The observed cluster substructures are more efficient lenses than predicted by CDM simulations, by more than [10 times]. We suggest that systematic issues with simulations or incorrect assumptions about the properties of dark matter could explain our results,” researchers describe in an article published in the journalScience.
Spectroscopic analysis from VLT data allowed astronomers to measure velocities of individual stars within the galaxy clusters. This allowed them to determine the amount of mass, includingdark matter, in the distant galactic clusters.
“We have done a lot of careful testing in comparing the simulations and data in this study, and our finding of the mismatch persists. One possible origin for this discrepancy is that we may be missing some key physics in the simulations,” saidMassimo Meneghettiof the INAF (National Institute for Astrophysics)-Observatory of Astrophysics and Space Science of Bologna in Italy.
By bringing together different types of telescopes, examining targets over a range of frequencies (light, radio, infrared, ultraviolet, etc.), astronomers are better able to piece together processes occurring in and around distant targets. The supernova explosion of a distant star, for instance, will radiate in high frequencies — gamma rays and X-rays, before cooling off, radiating in visible light, infrared, and radio waves. By combining observations over all these frequencies, it is possible to develop a comprehensive record of an event.
The Nancy Grace Roman Space Telescope, scheduled for launch in the mid-2020’s, will examine even more distant galaxy clusters, attempting to unravel the mysteries ofdark matter.
This article was originally published onThe Cosmic CompanionbyJames Maynard, founder and publisher of The Cosmic Companion. He is a New England native turned desert rat in Tucson, where he lives with his lovely wife, Nicole, and Max the Cat. You can read this original piecehere.
Astronomy News with The Cosmic Companionis also available as a weekly podcast, carried on all major podcast providers. Tune in every Tuesday for updates on the latest astronomy news, and interviews with astronomers and other researchers working to uncover the nature of the Universe.
Story byThe Cosmic Companion
Exploring the wonders of the Cosmos, one mystery at a time.Exploring the wonders of the Cosmos, one mystery at a time.
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