This video is about astrophysics
astrophysics is the branch of astronomy
that deals with the nature of cosmic
objects astrophysics relates to the
stars planets and everything in between
it is about how they form function and
what they are made of the first type of
star here the red dwarf star is also the
most common star in the universe these
stars are small and lived for a very
long time some red dwarfs can live for
up to 10 trillion years the main there
are two main reasons these stars live
for so long 1) since they are very
small
they are under far less pressure from
gravity 2) The inside they're
inside their mass they have large
currents which transport the various
gases mainly hydrogen, across their
entire star from the outside to the very
center they effectively make sure that
these stars use up all of their fuel
before dying the second type of star
here the yellow dwarf star, is also the
star that we orbit these stars are
mid-sized stars that generally live for
around 10 billion years, when a yellow
dwarf star runs out of its main source
of fuel hydrogen it begins to expand
when it expands it grows to many times
its size and becomes what is known as a
red giant a red giant star is very large
and glows red the temperature of the
Stars surface decreases but since the
star itself is now larger the total
temperature increases this expansion
will allow it to begin merging and
fusing helium which effectively turns
helium into its new source of fuel
eventually once it exhausts all of its
fuel it it sheds its outer layers it
ejects away its outer layers into what
is known as a planetary nebula
a planetary nebula is a disk of gas that
surrounds a red red giant star that has
died at the center of a planetary nebula
there will be what is known as a white
dwarf a white dwarf is the remains of a
yellow dwarf star it's simply the matter
that has not been ejected into space the
white dwarf will glow white-hot and will
slowly fade away until it becomes a
black dwarf which is simply the white
dwarf without any of the heat the third
type of star is a blue giant star blue
giants are the largest and hottest stars
in the universe they also have the
shortest lives they live for only about
100 million years on average because
they're extremely extremely large size
puts a very large amount of pressure
from gravity onto them
this forces them to use up their fuel
very fast when a blue giant star uses
that uses up its hydrogen its main
source of fuel it begins it begins to
collapse inward when that happens the
collapse causes the core of the star
where nuclear fusion and therefore the
energy generation takes place to
increase in temperature this increase in
temperature will then allow for they
start to begin fusing heavier elements
like helium and everything that comes
after that these new elements will be
fused faster and faster they'll be fused
faster than the element before them so
helium will be used faster than hydrogen
and anything that comes after that will
be fused even faster and so on until it
gets to iron when it gets to iron it can
no longer do anything because iron does
not produce energy when it is fused and
compressed here the star begins to
collapse one last time the outer layers
of the star fall into the core and then
suddenly bounce off it in a massive
explosion in what is called a supernova
explosion these are the largest
explosions in the some of the largest
events in the universe they can outshine
entire galaxies some supernovas can
produce what is called a gamma-ray burst
a gamma-ray burst in a stream of highly
charged particles that shoot out of a
star these bursts are extremely powerful
and if one were to hit earth it would
destroy the ozone layer and irradiate
and kill much of the planet a neutron
star is one of the byproducts that could
occur from the death of a large blue
giant star if the core is below a
certain mass then during the supernova
the core will collapse but will not
collapse indefinitely it will not
continue collapsing eventually it will
stop and form an object that is made of
extremely dense core matter the all the
atoms and different protons and
electrons of the atoms are squeezed into
neutrons that's why it's called a
neutron star a neutron star because it
holds the mass of a star's core but is
much smaller it's about as small as a
city it is extremely dense an atom is a
traditional atom is mostly empty space
however in a neutron star all the empty
space is filled with neutrons there it
there is no empty space at all it's all
completely clogged this makes the matter
of neutron stars extremely heavy
one teaspoon weighs billions of tons a
black hole is the most extreme remain of
a dead blue giant star if a star's core
is three times more massive than our Sun
it will keep continue will continue
collapsing beyond even a neutron star
eventually it gets to a point where the
density
of decor is infinite and that is called
the singularity a black hole has
infinitely strong gravity beyond a
certain point this gravity is so strong
that beyond what is known as the event
horizon light cannot escape it that is
why we call a black hole because the
light even the light is dragged in we
cannot see what happens inside at a
certain area however light actually
begins to orbit the black hole the same
way that a planet would orbit a star
also the time close to a black hole
slows down due to the immense gravity
there are two types of black holes
stellar-mass black holes which form from
large stars dying and supermassive black
holes which form from which are believed
to form from multiple different
stellar-mass black holes colliding and
merging supermassive black holes are
often found in the center of galaxies
the last part is about planets planets
are simply formed from the matter that
is not used up by the star there are
many different types of planets rocky
rocky planets like Earth gas giants like
Jupiter and Saturn ice giants like
Uranus and Neptune earth-like planets
which are planets that are that have
similar atmospheres to earth we have not
observed any earth-like planets yet but
they may exist carbon planets a type of
possible planet made in a solar system
that has more carbon than it has oxygen
this is thought to be possible near the
center of the galaxy desert planets like
Mars that have very little or no water
on the surface ice planets ocean planets
which is a type of planet that could
have that has its entire surface covered
in water
these are some examples of the
classifications used for planets in our
own solar system there are a few
different types of planets first there
is Mercury Venus and Earth but Earth and
Mars which are rocky planets Mars is
also considered to be a desert planet
there are gas giants Jupiter and Saturn
and Uranus and Neptune being ice giants
Pluto was at one point considered to be
an ice planet until it was demoted to
the status of a dwarf planet
however they are actually extrasolar
planets or planets that orbit other
stars that are even more strange than
the ones that we have here for example
there is a type of planet called a hot
Jupiter a hot Jupiter is simply a gas
giant that orbits very close to its star
closer than mercury does to our star hot
Jupiters take mere days to orbit their
star and as a result of this their
atmospheres are hotter than that of any
other planet there's another type of
planet called a catonian
planet which is simply a hot Jupiter
which has had its entire atmosphere
blown off leaving only the solid core
most of these planets are hostile to
life however our telescopes have
detected many planets that orbit in what
is known as the Goldilocks zone of a
star this is simply the zone that of a
star's orbit where it is not hot enough
to cause water to evaporate but is not
cold enough to cause water to freeze
over our earth happens to orbit exactly
in the middle and there are many other
planets that have been found in this
situation however we have yet to find a
good study of their atmospheres and
although we have found ideas of what
kind of gases those planets can hold
it's still difficult to confirm right
now however with the launch of the James
Webb Space Telescope in 2021 we should
be able to find better evidence of what
if an extrasolar planets atmosphere will
be like in one of the main goals of the
James Webb telescope is to analyze what
these planets are like and if life can
exist on them thank you for watching
this video I hope you learned some
things about what stars planets and
other astronomical objects are like and
I will see you in the next video
