Scalobaloba!
Hello, people. I'm Schwarza and welcome to another Astro Pocket!
That program that shows you that not even those great scientists and names of science
have their infallible theories. Look how controversial!
Today I'm going to talk about Stephen Hawking, the wisful Stephen Hawking
that guy who contributed a lot to science including black hole studies
He's the father of Hawking Radiation Theory so he's a very important guy that science has had
And today I'm going to talk about one of the most famous theories of this great British physicist
the one that says that dark matter would be composed of primordial black holes
Actually I'm going to talk about a big blow that his theory had suffered recently
on account of a large telescope that captured an image of an entire galaxy in just one click all in one go
The discovery does not completely rule out the famous notion of Stephen Hawking
that dark matter would be composed of primordial black holes
But they suggest that primordial black holes would have to be tiny to explain dark matter
Dark matter is a big mystery in Astrophysics
Physicists give this name for it  not because it is black the color of my t-shirt
but because we can not observe this dark matter
everything in the universe moves, orbits and rotates as if there were more mass than we can detect
there's mass but we don't know where it is because it is dark matter
Explanations for dark matter range from phantom particles called neutrinos to unknown particles
which would be part of the new laws of physics
In the 1970s, Stephen Hawking and his colleagues theorized that the Big Bang
may have created a large number of relatively small black holes - each one about the size of a proton
These tiny old black holes would be hard to see
but would still have a great gravitational pull on other objects - the two known properties of dark matter
Until now  this theory could only be tested for primordial black holes heavier than the moon
But as technology improved, scientists were able to take sharper pictures of outer space
The Hyper Suprime-Cam (HSC) digital camera at the Subaru telescope in Hawaii
is an advanced piece of imaging technology
that can take a picture of the entire Andromeda galaxy (the galaxy closest to ours) in all in one go
Masahiro Takada and his team at the Kavli Institute of Physics and Mathematics of the Universe in Japan
used this camera to look for primordial black holes
their results were published earlier this month in the journal Nature Astronomy
As you already know the black holes don't emit light, they are totally dark
and hidden in the vastness of the cosmos
but supermassive black holes like  Messier 87 galaxy that generated that image of the black hole
are surrounded by bright disks of hot matter they are the accretion discs
the primordial black holes however they are billions of times smaller minors until my dignity
and they don't have  visible and bright matter around them
But scientists can look for other evidence of the existence of these objects
the gravitational field of these objects is very intense and strong
and it makes a curvature of the light that we call the gravitational microlens
The telescopes found microlenses of black holes  of a star for a long time
A black hole passing in front of that star will distort its light  making it shine
the smaller the black hole the faster the flash
Takada says that if a microlensing object has a solar mass in other words the mass of the Sun
the time scale of the microlens flash is from a few months to a year
But the primordial black holes they sought had only a small fraction of that mass about the mass of the moon
It means their flashes would be much shorter.
The HSC is "unique," Takada said in that it allows them to take pictures of all the stars
in the Andromeda galaxy at the same time
Takada and his team took about 200 photos of the Andromeda galaxy for 7 hours on a clear night
And in that period they found only one potential microlensing event
If primordial black holes constituted a significant fraction of the dark matter
Takada said, they should have seen about 1,000 microlens signals
"Microlens is the gold standard for detecting black holes or discarding them"
said Simeon Bird, a physicist at the University of California
he says that "this work excludes primordial black holes as dark matter in a variety of masses
where previous constraints were not as strong or as robust as this new one
and it's a very good result according to our friend Bird
Was this the last nail in the coffin? Is Hawking's theory really dead?
Can we totally rule out that dark matter is made up of primordial black holes the size of a button?
It's really smaller than it
according to Bird and Takada, who say that the primordial black holes of a certain range of masses
that have not yet been totally eliminated for physicians and researches
Then there's the possibility that Stephen Hawking is right
There are still some masses where the restrictions are weak around 20-30 solar masses
and they could represent 1% to 10% of dark matter
and there is still a window in lower masses like the mass of a very small asteroid
"Our physicists are very excited because there is still a window," Takada said
The data can not exclude these tiny black holes
because the flashes of those black holes would be very short so we need to think of another method to do it
However there was a "flash" detected in his research
Although it just a single preliminary result could end up being incredibly important:
the first detection of a primordial black hole
which would be an innovative validation of some of Hawking's works
"Only one observation is not so convincing," Takada said
"If it were really [a primordial black hole] we should continue to find more of them around."
Scientists continue to use HSC to look for more microlenses
May be the  Stephen Hawking's theory of dark matter has being discarded because of this research
And this is not bad ...I use to listen many people saying  "such a physic is wrong"
"the theory fell, did you see? Science is anything"
That's not it ... Science works this way
sometimes you have a theory and another one better and more elaborated appears also with more evidences
and it drops the previous one
That's how it works!
When you eliminate an idea it is very good because it means that you have found a path
that goes to the exact description of that phenomenon
So if we dismiss this Stephen Hawking theory that dark matter is made up of primordial black holes
then it means that we don't need to waste our time with this idea and go to other
and so Science evolves!
So it is not a defeat of Science and not a defeat of Hawking
he gave us tools so that we could study and eliminate some possibilities and thus find the truth
although truth is also a very strong word
it's better to say " the evidences"
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Anyway ... I've already said too much
I hope you have a great day and hugs!
Hasta!
Subtitles by Giovanna de Castro
