Astrophysics
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| EHT, Event Horizon Telescope captured the first-ever image of a black hole in the center of a massive galaxy.
For
a long time, scientists were able to prove that an object called a black hole
could exist in the universe. Yet there was no actual evidence of it to support
this hypothesis. On April 10, 2019, scientists from the Event Horizon Telescope
have finally released the first-ever image of a black hole located at the
center of a massive galaxy called M87. This is a breakthrough in astrophysics
and in the history of science because not only it proves the existence of black
holes as predicted by Albert Einstein's theory of general relativity, but it
exactly matches our computer simulations of what we thought a black hole might
look like.
The
black hole image released by EHT is in a galaxy so far away from us. This
galaxy is 55 million light-years away from Earth. In other words, the light
detected by our telescopes from Earth had already left the M87 galaxy 55
million light-years ago. A light-year is equivalent to the distance that a beam
of light can travel in one year. Thus, 1 light-year is equal to 5.8786×10^12
miles or to nearly 6 trillion miles —given the constant speed of light of
186,000 miles per second. To make it possible to capture such far object,
scientists needed an Earth-sized telescope. Obviously, this is not doable, so
they have created a virtual telescope by combining eight radio telescopes from
different locations around the globe. A 29-year-old scientist Katie Bouman was
behind this brilliant achievement. She wrote the algorithms that made it
possible to collect the messy data from different telescopes and process an
image from it. It's very inspiring to see a grad student doing what many other
scientists couldn't do. Kati Bouman deserves a lot of credits for her great
accomplishment because it will tell us more about our universe as we learn more
about black holes. Her name will always be remembered as the scientist who
proved that once again Einstein's predictions were right.
I
want to back and explain the origins of the idea of the existence of black
holes and how it brought us to this new discovery. In 1915, Albert Einstein
introduced the concept of gravitational lensing which describes when light is
traveling through space, it can bend as it comes across a dense object such as
our sun. As the light bends, it creates a ring of bright light appearing to
surround the sun. This light might appear as if it represents the true location
of a star in space. But, that star is actually located behind the sun.
Throughout the process of developing his theory of general relativity, Einstein
calculated the correct value of the light of the stars bending around the sun.
This was only possible after he came up with the revolutionary idea that
redefined the notion of gravity. Back in the seventeenth century, everyone
thought of gravity as Isaac Newton had defined it. A strange force acting on
objects in the heavens. Instead, Einstein creates a new dimension he called
space-time that curves the fabric of space enabling heavy objects to shape the
area around it based on their density. Any small object falling in the dip
these objects falls into an orbit. That's why the Earth orbits around the sun.
It boggles my mind how a human being on Earth was able to get to such discovery
just by using a simple thought experiment at his office.
The
name itself black hole might be misleading for those who don't know what a
black hole is. Think of a black hole as an object that has a spherical shape.
It is a region of space-time exerting a dense gravitational force on itself, so
strong that no object could escape from it. Not even light, the fastest known
thing in the universe. Black holes could exist in different locations in space
depending on their sizes. A small black hole could form after the death of a
big star that collapses on itself. For a star to become a black hole it must be
at least 3 times the mass of our sun. So, don't worry, our sun will never turn
into a black hole and suck us all in it. Black holes could also be found at the
center of a supermassive galaxy like the M87. The image released by EHT shows a
bright yellow and red light in the shape of a spinning disc around the event
horizon. That's the dust and star stuff that is being heated up by the
gravitational pull of black hole.
Black
holes have 2 main components: the event horizon that represents the boundary of
the spherical shape of the black hole and at the center of it we find something
we call the singularity. The gravitational pull at the singularity is so
powerful that strange things start to happen, time stops altogether. This has
been proven with mathematics by many scientists and astrophysicist including
Steven Hawking. If you go through the singularity, assuming you don't die instantly,
from your perspective time seems to run so fast. From an outside viewer, you
would be first standing still then disappear in the darkness. As you fall into
the black hole, you will experience strong gravitational pull that will stretch
your feet and break parts of your body into little shreds. Then those parts
will get divided equally at a microscopic level just like in a cellular
division phase. This will keep going until all the cells and particle of your
body melts into hot plasma and disappears into the unknown. Scientists have a
term for this, they call it "spaghettification".
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