Aloha! Welcome to Learn the Sky. My
name is Janine and in this video we're
going to review the types of nebulae
that exist. A nebula is defined as a
cloud of gas and dust that consists
mostly of hydrogen. Typically there are
other trace elements that exist within
the cloud such as water, formaldehyde
alcohol, and other trace elements. But
they mostly consists of hydrogen. Now,
before we dive into the different types
of nebulae, let's go over the singular
and plural versions of this word just so
there's no confusion. So when we talk
about a nebula that's when we're looking
at one specific nebula, so that's a
singular version of this word. But if we
say nebulae that means that is plural so
more than one nebula we say nebulae.
There are five main types of nebulae and
they can be broken down into two
categories. The ones listed at the top
such as absorption, reflection, and
emission are known to be diffuse
nebulae. So, they do not have the
definitive shape. In fact they're often
named after objects that they resemble.
The other types of nebulae include
planetary nebulae, and supernova remnants.
The shape of these nebulae are
typically spherical in structure. Now
let's review and take a look at what
these different types of nebulae look
like. So our first one that we're going
to examine is called an absorption
nebula. The way this one works is
that it is such a dense dark cloud that
light cannot pass through it . It almost
absorbs that light that is passing
through it. The classic example of an
absorption nebula is the Horsehead
Nebula, which is located
Orion right near the belt and sword.
As you can see there's no definitive
shape. It's not spherical, it can be
considered to be asymmetrical, but many
nebulae are named after what they
resemble. If you take a look at this
you can sort of see how it would
resemble a horse's head. Another classic
example of a dark nebula, or absorption
nebula, is a snake nebula. This one is
located in the constellation called
Ophiuchus. You can just see here that
this cloud of gas and dust is just so
thick that light cannot pass through it.
The next type of nebula is called an
emission nebula. These are clouds of
gas and dust that are glowing brightly
due to fluorescence. Inside this cloud
of gas and dust, there are tiny stars
that are starting to be born. What
this does is- it heats up the cloud and
it causes it to glow. The Orion
Nebula in the constellation of Orion is
a classic example of an emission nebula.
Where would you find this- if you
would look at the belt stars of Orion,
right here, the Orion Nebula sits right
in his sword. There are other
spectacular nebula right around the belt
stars as well. In fact this is where the
Horsehead Nebula is as well. Here are
other great examples of emission nebulae.
To the left we have the North America
nebula.
This is located in the constellation
Cygnus and as you probably notice it
does resemble a continent of North
America. But even cooler, on the right is
called the ghost nebula. This is
located in the constellation Cepheus.
It's just so cool how you have this
cloud and inside of it you have a little
baby star. That star is starting to
heat up a nebula and it glows. It
does look ghost-like for sure. So again
another example of how we are naming
things after what they resemble. Even,
here, these kind of look like little
ghosts coming out as well. The third type
of diffuse nebulae, or irregular shaped
nebulae, would be the reflection type.
This is unique in the sense that it is
illuminated.This cloud of gas and dust
is illuminated by the glow of nearby
stars. Typically reflection nebulae
are more blue in color because the dust
tends to scatter blue light more
effectively than red. So typically these
nebulae are more blue in color. Te
Pleiades star cluster located in the
constellation Taurus is another classic
example of this type of nebulae. This
next nebula I'd like to share with you
is called the Trifid Nebula also known
as Messier 20. This one is very
interesting because it is a rare
combination of the three types of
diffuse nebulae that exist. So, when we're
looking at this picture, we're looking
towards the center of the Milky Way
Galaxy and right through the
constellation Sagittarius. I'm going
to bring your attention to this area and
this is the part of the picture that we
are going to zoom in. and this is what we
find. So the Trifid
nebula shows each type of diffuse
nebulae that exist. So, the dark portions.
all right in here, that is considered an
absorption nebulae, or a dark nebula.
Then the pink areas, all throughout here, would be considered to be an
emission nebula. Then up here, this
bluish area is considered to be a
reflection nebula. So again, the fact that
these are all combined into one type is
very, very interesting. This is one of
those few spots in the sky that
definitely attracts many different types
of astronomers because you get to see
three types in one specific astronomical
object.
So just to recap. So far we have explored
the diffuse types of nebula. The ones
that do not have a definitive shape.
Those were absorption, reflection, and
emission. Now let's go ahead and look at
the types of nebulae that do have a
definitive shape. Our first type of
spherical nebulae are the planetary
nebulae. The name is slightly
misleading, because these types of
nebulae have nothing to do with planets. They were first named when William
Hersche,l in 1785, observed these through
a telescope. He thought that they
looked very similar to the spherical
shape of a planet, so that's why they
were named planetary nebulae. But in fact,
this object is really a dying star in
the end stages of its life. This is
eventually what will happen to our Sun.
So this star, right here, in the center is
not truly a star anymore because it's
not undergoing fusion. It's run out of
hydrogen, helium, and all the elements
it was using at one time in its core.
This is all that's left- is this little
white dwarf star. It's the hot leftover
core of a main-sequence star, a
regular-type star. These outer layers
are the gases that are being blown off
the star. They really have some
beautiful shapes. So this is really at
the end stages of the star and typically
at the end of the red giant phase.
You have this little white dwarf left in
the center. So let's take a look at some
other ones. This is the Eskimo Nebula,
right here, in Gemini. You can probably
see while it has that name because it
definitely looks like an Eskimo with its
hood up. Then we have the Dumbbell
Nebula this is located in Vulpecula
which is known as a fox in the southern
hemisphere. If we were to go back to
this one this is known as the Cat's Eye
Nebula in Draco the dragon. The final
type of nebulae that we will examine is
called a supernova remnant. These are
some of the coolest looking nebulae that
exist. So how these form is that these
are the leftover remains of a supernova
explosion. You can really just tell
from this picture that this really looks
like it was blown to smithereens.
Everything is moving outwards from the
center. Typically within these
supernova remnants there are pulsars
inside of there. So, hot neutron stars
that are spinning very, very rapidly and
often send out radio signals. The one
that we're looking at here is called the
Crab Nebula located in Taurus. Let's
take a look at where that would be so if
you have Orion, right down here, and use
about stars to help you find the
v-shaped face of Taurus. Then you
come down to the lower horn, the Crab
Nebula is located right near the tip of
the horn in Taurus at the bull. So what's
interesting about supernovas is that
this is the celestial event that occurs
when all the elements on the
periodic table are created. Regular stars,
like our Sun, do not have the ability or
the mass that they need in order to fuse
together higher elements. The
largest element that any star could form
is iron and once iron starts to form
inside of the star it becomes unstable. The iron starts to absorb the energy
therefore causing it to be unstable
then kaboom that's when a supernova
occurs. This whole shell of clouds
and gas and dust is still expanding to
this day. If you were to look up
different types of pictures of super
number supernova remnants they really do
have this this spherical but also
irregular structure, which really
just looks like it was blown up. Let's
review the five different types of
nebulae that exists and the two
different categories that they are in. So,
all the nebulae that are listed at the
top- those are a regular shaped nebulae.
They're diffuse, they do not have a
definitive shape. If they do have a
shape sometimes their name will reflect
that shape like the Horsehead Nebula;
which is considered to be a Dark Nebula
in the sense that it's really absorbing
the light that is surrounding it because
the clouds are so thick that light
cannot pass through. We also have
reflection nebulae. These are the
ones that are reflecting the light that
are coming from nearby stars. The dust
that is located within the cloud is
scattering the light ,causing that blue
color. Then the final diffuse type of
nebula are emission nebulae. These
are ones that are glowing because the
stars that are located inside are
starting to become hot and it causes all
the gas inside to glow due to
fluorescence. Now we have the spherical
type shape.
That one would be the planetary nebulae.
These are the nebulae that are dying they are at the end of their life.
They're just throwing off all the outer
layers, but they have this very unique,
sometimes almost a series of rings
around rings with each other. Even
though they're named planetary nebulae,
they do not have anything to do with
planets. They just inherited that name
because at one time astronomers thought
it looked like planet. Then finally
we have supernova remnants and these are
violent reactions of a dying star in
which pretty much the whole thing was
blown apart many different elements were
created. It also creates a super cool
shape. Often there are little pulsars
inside of here, little neutron stars that
are spinning rapidly and giving off
radio stars. Thank you so much for
watching! If you have any other interest
about constellation or different types
of celestial objects that exist out
there, feel free to subscribe to my
channel. I encourage you to keep
going outside observing the stars.
Then as you start to learn the sky share
what you have learned with others and
inspire them to go outside as well.
Thanks for watching!
