Cosmologists know that dark matter must exist.
If it didn’t, the rate galaxies spin would tear them apart—
so there must be something unaccounted for generating the gravity that’s holding them together.
Something that doesn’t interact with regular matter in any other way that we’ve detected yet.
What exactly that something is, is anyone’s guess—and there are a lot of candidates to choose from.
Now though, thanks to new observations using the Hubble Space Telescope,
scientists believe they have strong evidence for one of the most widely accepted
and coolest dark matter theories.
The specific form of dark matter that astronomers think they’ve detected is cold dark matter.
Cold refers to the slow speed the particles move,
with hypothetical warm and hot dark matter particles moving faster.
Any of these forms of dark matter could theoretically come together to form a scaffolding.
This scaffolding would have a gravitational pull strong enough to hold stars and galaxies embedded in it.
But only slow moving “cold” dark matter particles could congregate in smaller clumps,
ones with the mass of say, a commercial airliner.
These clumps would be too small to hold onto small galaxies,
meaning that detecting these smaller clumps is impossible using the traditional methods
of looking for embedded stars.
So, astronomers devised a new way of searching for them, one that relied on things lining up just right.
Astronomers used the Hubble Space Telescope to hunt for quasars,
the regions around active black holes where superheated matter emits tons of light.
But not just any quasar would do—
Hubble had to find a quasar that was almost perfectly aligned behind an entire massive galaxy.
Of course, under normal circumstances here on Earth,
putting one enormous thing in front of a smaller thing is not conducive to seeing that smaller thing.
But in a cool twist—pun intended—the gravity from the galaxy bends the path of the quasar’s light
in such a way that it’s visible to Hubble.
In fact, the galaxy actually magnifies the quasar and copies its image four times.
This technique is known as gravitational lensing.
But the four copies of the quasar’s image are not identical.
They get distorted by clumps of dark matter that warp the space the quasar’s light travels through.
By comparing the warped images to how they should look if there were no dark matter,
astronomers can determine the mass of the dark matter clumps that otherwise would have been invisible.
But finding the right candidates to observe wasn’t easy.
The researchers had to pore over ground-based surveys to find the gravitational lenses.
They found 8 from which to draw their data, with the quasars located about 10 billion light-years away,
aligned just right behind galaxies that are 2 billion light years from us.
After years of taking and analyzing images, these latest results are pretty tantalizing.
The researchers determined that the light from the quasars was distorted in ways
that suggest small clumps of dark matter are out there,
providing what they call the strongest evidence yet that dark matter is of the cold variety.
Not bad work for the Hubble Space Telescope, which is pushing 30 years of service.
Hubble took the images in the near-infrared range,
since quasars are best seen with infrared light.
When future infrared space telescopes like the James Webb
and Wide Field Infrared Survey Telescope launch,
they’ll be able to conduct follow up studies in greater detail.
We still don’t know what exactly this “cold” dark matter is,
but thanks to some clever work to bend light and space to our advantage,
we think we’re getting closer.
Do you have a pet theory of what Dark Matter could be?
My personal favorite: WIMPS.
Just because of the acronym.
Let us know your thoughts down in the comments.
You know, I feel like we talk a lot about how great the James Webb Space Telescope is going to be,
but how close are we to actually launching this amazing thing?
Check out this video to find out.
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