it was once thought that the earth was the center of the universe until more or less
five centuries ago nicolau copernicus propose that indeed
the sun was the center of the universe as astronomy was evolving was perceived
that in fact the sun was only one star among other billions of stars
the difference is that the sun is much closer as the stars are far apart
today we know that the earth or the sun
is far from being the center of the universe
they are located in a galaxy that is only one among billions of other galaxies
every galaxy has its appearance
composition and size, and that's what we'll see in today's video
What are galaxies?
Introduction
Are cosmologists all right? here who speaks is the vini of the channel singularity
this is the fourth video of our mini course on astronomy
if you have not seen the previous videos click on the card understand what
are the stars, the solar system. birth to adolescence and death
of the stars.
formerly the concept of
galaxies with nebulae, because if you could observe a galaxy with the naked eye
it is totally irregular, looking like a nebula
the galaxy of andromeda when it was observed for the first time was named
of andromeda nebula
there are several types of galaxies
elliptic and irregular spirals
there is a great variety
in the amount of stars you can find in a galaxy
the Milky Way galaxy, that we are. has 400 billion stars
seems a very large number, however, there are galaxies such as:
the galaxy of andromeda that is the galaxy closest to us
that one has trillion stars, this is a very large number though
there is a galaxy that is even larger
The IC 1101, it has 100 trillion stars it has a diameter of six million light-years
This is the size of the sum of some galaxies
such as: The great cloud of Magellan
the small cloud of magellan, the galaxy of andromeda and the galaxy of the triangle
galaxies participate in galactic groups
which are called clusters of galaxies, our cluster of galaxies called the Local Group
which is where our galaxy Milky Way is located, has 54 galaxies
the nearest galaxy is the galaxy of andromeda that is 2,5 million light-years
one light-year equals 9.5 trillion kilometers
The distances between these galaxies are enormous
which can reach up to 25 million light-years away
even if these galaxies are in the same cluster
which in this case is the local group
believed that the matter of galaxies
only one-sixth of the total amount of matter
that matter we can not identify is dark matter
This is the matter that generates most of the gravitational fields of galaxies
it accounts for 24% of all universe matter
its functioning is one of the biggest puzzles in science maybe it's a type
of matter that is in another dimension may be a matter that only
interact with the light, anyway scientists do not know exactly how to
this matter works
before we understand how galaxies
will self-destruct, we need to understand how they are formed
How do galaxies form?
there are several theories for how a galaxy forms
the main one is that the black holes came before the galaxies
if we consider that most of the galaxies have in their center a black hole
for example the Milky Way has a black hole sagittarius A.
That a giant black hole classified as supermassive
Now let's go back to more or less.
thirteen billion years ago in time, shortly after the time of the Big Bang
this is the moment when the matter was well dispersed and the first stars were forming
as the great inflation of the universe was happening, the matter was very abundant
this made the majority of the stars supermassive, that is, they had a
very large matter
black holes originate from supermassive stars, so it is quite likely to say that about 20% of
stars that have formed have become black holes
because of this large amount of black holes it is likely that they began to
attract and merge into larger black holes
this would cause the black holes to become supermassive black holes
Supermassive black holes have a large gravitational field
then it is very likely that these
Holes attracted more matter ie more stars and these stars attracted
more stars still forming galaxies
but what will be the end of the galaxies?
the galaxies do not have a fixed time
still life, they can end up in different ways
it depends on how much gravity the universe has, and the amount of dark energy
in short, scientists need to know
if the universe will continue to expand, if it will begin to contract
or if the expansion begins to accelerate
there are basically three endings for galaxies
The Big Crush, Big Freeze and Big Rip
there are other ways but these are the main
the Big Crush would be that the universe would stop expanding
it would begin to contract rather than expand, this would cause the universe
start to shrink in size to some extent make another big bang
this would destroy the galaxies but would also re-create them
Just as some religions propose
the Hindu religion is the only one of the great
creeds of the world dedicated to the idea that the cosmos itself goes through a
immense, really an infinite number of deaths and rebirths
the Big Freeze would be that the universe would continue to expand the distances between galaxies
continue to increase and the universe would be colder.
this would mean that as time goes by the stars begin to die and
generate more heat to generate new stars
another possible end is the big-ip in this model universe would continue to expand
and accelerate expansion, that would cause galaxies to drift apart
and the atoms began to disintegrate according to time or atoms
would begin to exist more, but as I said in the beginning
depends on the amount of dark energy that exists in the dark energy universe and
dark matter and dark matter will be covered in a specific video
here on the astronomy channel
another possible end as I said at the beginning of the video
are the black holes, it's just a hypothesis but it may be that
happens that the black holes suppress all the matter of the universe
this would make the universe totally dark
only with black holes would these black holes emit hawking radiation as
Stephen Hawking proposes, and this would mean that according to
They would begin to be vapor and so would be the end of the galaxies and everything in the universe
galaxies are essential for life
they harbor stars that can harbor planets and harbor intelligent life
like ours, the galaxies are gigantic there are about 2 trillion galaxies
throughout the universe
if we consider that in most galaxies there are a few billion stars and that there are 2 trillion galaxies
as Carl Sagan would say
"If there is no life in the universe, it is a great waste of space" - Carl Sagan
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See you next time!
Subtitles: Vinícius Dutra
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