Podcaster: Richard Drumm
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Title: UNAWE Space Scoop – A Missing Ingredient
Organization: 365 Days Of Astronomy
Link : http://365daysofastronomy.org/ ; https://spacescoop.org/en/scoops/2035/a-missing-ingredient/
Description: Space scoop, news for children.
The Universe is full of unanswered questions. And more than a few unquestioned answers!
One of the biggest questions astronomers are trying to answer is what is the Universe made of? OK, sure, we know about protons, neutrons & electrons already.
But astronomers also know that the Universe is full of dark matter, but we still don’t fully understand it…Dark matter is a mysterious and peculiar material that got its name because it doesn’t give off any light – it’s totally invisible at wavelengths our eyes can see.
Dark matter remains as elusive as Alice in Wonderland’s Cheshire Cat. You can only see its grin (in the form of gravity) but not the animal itself. Yet, astronomers think there’s 5 times as much of this strange material in the Universe as there is normal matter that we can see.
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Transcript:
This is the 365 Days of Astronomy Podcast. Today we bring you a new episode in our Space Scoop series. This show is produced in collaboration with Universe Awareness, a program that strives to inspire every child with our wonderful cosmos.
Today’s story is….A Missing Ingredient
The Universe is full of unanswered questions.
And more than a few unquestioned answers!
One of the biggest questions astronomers are trying to answer is what is the Universe made of?
OK, sure, we know about protons, neutrons & electrons already.
But astronomers also know that the Universe is full of dark matter, but we still don’t fully understand it…
Dark matter is a mysterious and peculiar material that got its name because it doesn’t give off any light – it’s totally invisible at wavelengths our eyes can see.
Dark matter remains as elusive as Alice in Wonderland’s Cheshire Cat. You can only see its grin (in the form of gravity) but not the animal itself.
Yet, astronomers think there’s 5 times as much of this strange material in the Universe as there is normal matter that we can see.
We know that dark matter exists because we can see the gravitational effect that it has on the things around it.
Like seeing paw prints in the snow made by an invisible dog.
We know that it mostly hangs out around galaxies.
We believe it’s sort of the glue that holds ‘em together!
So what’s this Missing Ingredient business all about?
Well, astronomers have made an exciting discovery.
Something may be missing from our understanding of how dark matter behaves!
This was found by combining data and images from the Hubble Space Telescope and the European Southern Observatory’s VLT, the Very Large Telescope at the Paranal Observatory in Chile.
The team of mostly Italian astronomers investigated galaxy clusters in their study.
Galaxy clusters, as you might guess, are groups of galaxies that are clumped together.
They’re also where most of the Universe’s dark matter is found.
In these galaxy clusters, dark matter is heaped up like a mountain range, with lots of high peaks and lower valleys.
The team created maps of this to understand how the dark matter is spread out in 11 galaxy clusters.
They did this by sort of reverse engineering the distortions of background galaxies seen in photographs of the galaxy clusters.
The team compared the dark-matter maps they’d made with samples of simulated galaxy clusters with similar masses, located at roughly the same distances as the observed clusters.
The clusters in the computer simulations did not show the same level of dark-matter concentration on the smallest scales.
These are the same scales associated with individual galaxies in the cluster as seen out in the Universe.
They were surprised to find that smaller lumps of dark matter, like the lower valleys in a mountain range, are much stronger than they previously believed.
They found that small-scale concentrations of the dark matter in clusters produce gravitational lensing effects that are 10 times stronger than expected.
This likely means there’s something missing in our understanding of how dark matter behaves with stars and galaxies throughout the Universe.
A missing ingredient.
This is from the scientific paper’s abstract:
“We report that observed cluster substructures are more efficient lenses than predicted by CDM simulations, by more than an order of magnitude.”
– Substructures are small concentrations of dark matter.
– I think “more efficient lenses” means that the dark matter is, well, lumpy!
– CDM is cold dark matter.
– An “order of magnitude” means it’s 10 times as large.
“We suggest that hitherto undiagnosed systematic issues with simulations or incorrect assumptions about the properties of dark matter could explain our results.”
Heh. I’ll bet that it’s both!
There will be many more studies conducted in the future to help uncover the mysteries of dark matter!
This team looks forward to continuing their stress-testing of the standard dark-matter model to pin down its real nature.
Hey, here’s a cool fact!
Go to Google and do a search for gravitational lensing. Then click on “images”.
See the squiggly lines and funny shapes in the images? These are background galaxies!
They appear strange to us because their light has been bent out of shape due to the pull of gravity from the cluster’s galaxies & dark matter in the foreground!
Gravitational lensing is the effect that was used to map the dark matter shown in those images!
The gravity of dark matter magnifies & warps light from distant background objects, sort of like a funhouse mirror, producing distortions and sometimes multiple images of the same distant galaxy.
The higher the concentration of dark matter in a cluster, the more dramatic its light bending.
Cool!
Thank you for listening to the 365 Days of Astronomy Podcast!
End of podcast:
365 Days of Astronomy
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