Category: gravitational lensing

New Method For Tracing Dark Matter Reveals Its Location, Abundance As Never Before

“By measuring the distorted light from distant galaxies behind a galaxy cluster, scientists can reconstruct the total cluster mass. In every galaxy cluster, the majority of the mass is outside of the galaxies: there is a huge dark matter halo. The intracluster gas, however, may be distributed differently, as normal matter can collide and heat up, emitting X-rays. But individual stars, ejected from galaxies, should trace the same path as the dark matter. In a cosmic first, scientists measured this intracluster light, and found it traces out the dark matter perfectly.”

If you want to know where the dark matter is located in the Universe, you had to infer its presence and abundance by measuring the gravitational effects it had on space. When it comes to large-scale structures, like galaxy clusters, this often involved exceedingly difficult reconstructions involving gravitational lensing, and relied on serendipitous alignments of observable background structures. But a new study has concocted an alternative method that works extremely well: just measure the intracluster light from stars that have been ejected from the component galaxies.

Well, with the first two clusters down, we have a verdict: it’s the best dark matter-tracer of all time. Come get the remarkable story today!

Hubble Views The Final Frontier For Dark Matter

“This phenomenon of gravitational lensing stretches galaxies into streaks and arcs, magnifying them, and creating multiple images.

It also enables us to reconstruct the mass distribution of the cluster, revealing that it’s mostly due to dark matter.”

When you look out at the distant Universe, you can see all sorts of things: stars, galaxies, clusters of galaxies, going as far back into the distant past as our telescopes can image. But where you have the greatest concentrations of mass, an extreme phenomenon emerges: that of gravitational lensing. Any foreground objects lying behind that mass will have their light stretched, magnified and distorted by the intervening matter. Recently, as part of the Hubble Frontier Fields program, the telescope followed-up on galaxy cluster Abell 370, and revealed the most spectacular gravitational lensing signal ever seen in a galaxy cluster. Most importantly, it provides some very strong evidence not only for dark matter’s existence, but for its presence distinct from any galaxies at all.

Come get the full story in images, videos, and no more than 200 words on this edition of Mostly Mute Monday!