Space it's infinitely big and there are an infinite number of things in it, but
there are not an infinite number of different kinds of things.
So this is my attempt to try and collect all of the different kinds of things in space in one video.
Looking up from our earth into the sky
we see our solar system at the center is our Sun the yellow dwarf star that's lived for about
4.6 billion years and will live for 5 billion more before burning out
Around the Sun orbit the terrestrial planets, which are made mostly of silicate rocks or metals and the gaseous planets
Which are split into the gas giants which are mostly made of hydrogen
and helium and the ice giants which are made of heavier elements like oxygen carbon nitrogen and sulfur.
In between Mars and Jupiter we've got an asteroid belt which is the relic of the stuff of the early solar system,
Which we think never formed a planet due to the strong gravitational effect of Jupiter
There are other asteroids in the solar system, some of which become meteoroids when they hit the Earth's atmosphere,
And we get comets which have highly elliptical orbits around the Sun and were caused by the outward motion of Neptune 4.5 billion years ago.
We also have dwarf planets
which haven't managed to clear their orbits of other objects like Ceres in the asteroid belt and Pluto and others in the Keiper belt.
Which is a region beyond Neptune similar to the asteroid belt but far wider containing many small bodies made of rock and metal.
And of course we have moons like our Moon and the moons around other planets. Beyond the Keiper belt
we have the Oort cloud a theoretical cloud of icy objects surrounding the Sun in all directions and
Finally, we have the heliosphere a large bubble around the solar system created by particles coming from the Sun called the solar wind hitting
Particles from the rest of the galaxy the interstellar medium, and of course we mustn't forget cosmic dust
microscopic collections of matter scattered throughout the universe.
Looking beyond our solar system we get to our galaxy the Milky Way made of about 400 billion other stars spinning in a giant spiral.
The solar system takes about
250 million years to orbit the Milky Way and it's done this about 20 times in the lifetime of our sun.
In the center of the Milky Way is a supermassive black hole with a mass
4.6 million times that of the Sun
We think there's probably a supermassive black hole at the center of every galaxy,
and they can have masses of up to a billion times that of our Sun.
When we look up into the night sky most of what we see are stars,
and there are many different kinds of stars in the galaxy. 95% of stars of main-sequence stars,
which break down into red dwarf orange dwarf and yellow dwarf stars.
Red dwarf stars are the smallest, much smaller than the radius of the Sun, but the longest-lived
Estimated to live for thousands of billions of years due to their slow burn
orange dwarf stars are a bit smaller than the Sun and will live for tens of billions of years and
Yellow dwarves like our Sun live for about 4 to 17 billion years before expanding into red giant stars
Smaller than red dwarfs are brown dwarfs which aren't really stars because they were never massive enough to create fusion in their cores
They're about the same size as Jupiter but have at least 13 times the mass
The brightness of many stars varies over time and these are known as variable stars
There are a few different kinds intrinsic variable stars
The luminosity actually changes due to a change in size whereas with extrinsic variables the brightness changes because of an orbiting companion
moving in front of it like a binary star system or extrasolar planets and
Some giant or supergiant stars have irregular changes in luminosity
Cepheid variable stars are very valuable to us because they've got large variations in both size and temperature with a very stable frequency
Because of this strong relationship between luminosity and the frequency they pulsate they're used to determine accurate distances in the universe
They're known as standard candles
much bigger than the main sequence stars are the blue giants with a radius of 1.4 to
250 times the radius of the Sun and much shorter lives existing for three to four thousand million years
At the end of their lives they can cool into red giant super giants or hyper giant stars
Red giant stars of a radius of 20 to a hundred times the radius of the Sun and burn for a few
Hundred million to two billion years before exploding to make a planetary nebula with their cores shrinking into a white dwarf star
The white dwarf star is also the final destination for orange and red dwarf stars. White dwarf stars
make up 4% the stars in the galaxy and are tiny and dense
Roughly the mass of the Sun squeezed into the size of the earth
When they're dead, no fusion is going on in their cores and they only glow due to their residual heat energy
They will live for trillions and trillions of years growing dimmer and dimmer until they end up as black dwarfs, which don't yet exist
Because the universe hasn't been alive for long enough
White dwarfs will be the final state for more than 97% of the stars in the universe
for the truly massive stars a different cosmic journey awaits
The red super and hyper Giants have much shorter lives with only 3 million to 100 million years
These colossal stars with radius is a hundred to two thousand times that of the Sun in their lives in humongous
Explosion known as a supernova where they throw off their outer layers into a nebula known as a supernova remnant
While the core collapses into either a neutron star or a black hole
Stars larger than 40 times the mass of the Sun are likely to collapse into a black hole
An object so dense and massive that not even light can escape its gravity
This makes them completely dark and at their centers a gravitational singularity rips a hole in the fabric of space-time
They are the most extreme and fascinating objects in our universe
For stars that are not massive enough to form a black hole
They collapse into a neutron star where the combined gravity of the insane mass of the star
Overcomes the ability of electrons to keep atoms separate the atoms collapse the electrons and protons
Combine into more neutrons and it forms an incredibly dense ball of neutrons like a giant atomic nucleus
They have a mass of about 1.4 times the mass of the Sun but squeezed into a radius of only 5 to 15
Kilometers, this is so incredibly dense a sugar cube sized piece of neutron star would weigh as much as Mount Everest
Neutron stars are normally left spinning very quickly, and they've got incredibly strong magnetic
Fields millions of times stronger than anything we've ever created on earth
this magnetic field spews out electromagnetic
Radiation at the poles and as they spin around it sweeps a beam across the universe making a precise pulse when it passes
These are called pulsars and some of them revolve incredibly quickly several hundred times a second, which is just mad
The neutron stars with the strongest magnetic fields are known as magnetars and they could be the explanation for mysterious signals
We see in the sky like soft gamma repeaters and anomalous x-ray pulsars. An x-ray pulsar is a binary system
Where a normal star in a neutron star are orbiting around each other the neutron star sucks matter from the main star
creating high energy beams of x-rays at the poles
I've covered the death of stars, but what about their births?
Stars formed from the gas and dust of the stars that exploded in the distant past clouds we call nebulae
Protoplanetary nebula is the final stages of the formation of a solar system the star and planets forming out of the gas and dust
There are many other kinds of nebulae too
An H II region is a cloud of ionized hydrogen gas where star formation is taking place
An emission nebula is where a nearby hot star ionizes its gas and then it emits light at different frequencies
however
If the light from the star is not energetic enough to ionize the gas, instead
It will scatter off it making a reflection nebula in some nebulae are so dense. They blocked light coming through
These are called dark nebulae in the final feature of a galaxy a star clusters
Which come in two categories globular clusters are tight groups of hundreds to millions of stars
which are gravitationally bound while open clusters are a few hundred stars that are more loosely spread out and are not
gravitationally bound. Until about a hundred years ago, we thought that the Milky Way contain all of the stars in the universe
Until Edwin Hubble showed that the Milky Way was just one galaxy of many and now we know that there are one to two trillion
galaxies in the observable universe
The Milky Way galaxy is a spiral galaxy
But other galaxies broadly break down into elliptical spiral and barred spiral galaxies
shell galaxies are elliptical galaxies which are made from
Concentric shells of stars. Lenticular galaxies fall somewhere in between elliptical and spiral
galaxies
Occasionally galaxies collide and interact. Because of this, some galaxies don't fit these broad categories
For example ringed galaxies have an empty core and a ring-like collection of stars around it
Which may have been caused by a smaller galaxy moving through the middle of the larger one and irregular galaxies
Are those that have a strange shape due to some interaction in the past
There are super luminous galaxies four times bigger than the Milky Way
But most galaxies in the universe are a lot smaller than ours and they're called dwarf galaxies
Containing a few billion stars about a hundredth the size of the Milky Way and often they orbit the larger galaxies
Some galaxies have very active galactic cores where material falls into the central supermassive black hole creating jets of particles
traveling close to the speed of light
These are called blazars if the Jets are pointing directly at us
But radio galaxies if the Jets is pointing away as all we see are the radio waves being emitted by the Jets
Quasars are the most distant and most energetic of the active galaxies. Their central core emitting up to a hundred times the
luminosity of the entire Milky Way
Now we get to the mysterious things in the universe
Things we see but don't understand
Gamma-ray bursts are insanely energetic bursts of electromagnetic
Radiation from distant galaxies and the brightest events that occur in the universe
We think that they come from massive stars exploding in a supernova or from mergers of neutron stars
fast radio bursts of mysterious short pulses of radio waves caused by some high-energy process
Generating as much energy in a millisecond as the Sun does in 80 years
Some of these fast radio bursts are repeating coming from the same source over and over again
And we have no idea what is causing them. Dark matter is a mysterious form of matter that gives galaxies extra mass
Without it. They would fly apart
Even though it makes up proximately 85% of the matter in the universe
We don't know what this dark matter is because it doesn't interact with our ordinary matter our best
Guess is that it's some form of undiscovered subatomic particle flying around in space
But we've got no evidence for this yet
The solar system and galaxies are held together with gravity because gravity pulls things together
But when we look at galaxies in the distant universe, we see that they're accelerating away from us
This is really weird because it means that there's a mysterious force throughout the galaxy that's pushing everything apart in an accelerating rate
Like a kind of anti-gravity
We call it dark energy and it makes up
68% of the energy in the universe
Even though we've given it a name
We've got no idea what it is as we go to the largest scales in the universe
We see galaxies clusters then super clusters and the dark voids between them. Then we get to the Cosmic Microwave Background
The signal from when the universe first became transparent
380,000 years after the Big Bang
Behind this we can't see anything with lights
But we will be able to peer behind it with gravitational wave astronomy right back to the Big Bang
Which is as far as we'll ever be able to see in the universe
This makes it the edge of the observable universe at 46 billion light-years away
We know that there's still stuff further away from us than that
But we'll never see it because it's traveling away from us faster than the speed of light
And I said at the beginning the universe is infinite, but we don't actually know whether the universe is infinite or finite
Does another mystery to be solved?
So that's the universe all in one go at least most of it
They did have to drop a few things for the sake of time
Let me know in the comments if you think I've missed anything
important and one thing that is finite is this
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Alright, thanks for watching and I'll see you on the next video