Greetings and welcome to the
Introduction to Astronomy.
One of the things that I like
to do in each of my introductory
astronomy classes is to begin
the class with the astronomy
picture of the day from
the NASA website that is
APOD.NASA.GOV/APOD.
And today's picture for
December the 3rd of 2019.
Well, it is titled M27:
The Dumbbell Nebula.
So what do we see here?
Well, this is one of the
objects from Charles Messier's
catalogue of objects
that looked like comets
but were actually not comets as
seen through small telescopes.
So comet hunting was something
very big back in the 1700s.
And objects that
looked a little fuzzy
would then be observed to
see if they were comets
if they were actually
objects moving
through our solar system.
And Charles Messier
catalogued a list
of a little over a hundred
of these objects that
were not that we're not comets
so that he would know which
ones that did not have
to watch continually.
And it includes lots of common
objects such as the Andromeda
Galaxy and the Orion Nebula
as well as many other star
clusters nebulae and even
I say as a galaxy there.
So what this one is M27 is
actually a planetary nebula.
And this is what happens at the
end of the life of a star much
like our own sun.
So this is what
our son could look
like in 5 or 6 billion years.
And what happens when a star
reaches the end of its life?
It exhausts its fuel.
And when it does
that gravity begins
to win the battle and gravity
starts to pull the star down.
Now, what has that
does it heats up
and the central portion will
become very hot as that does
it creates new
energy sources, which
cause the outer layers
to expand out into space.
So while the core is collapsing
down to a very dense object
here at the center
- a white dwarf star
the outer layers are being
expelled out into space.
So first, the star will become
very large a giant and then
a super giant and even
a hypergiant star.
And eventually those outer
layers can become unstable
and can be pushed
out into space.
So that's what
we're seeing here is
where those outer
layers of the star
have been expelled
out into space
and then at the
very center there
is a white dwarf star, which
is that compact core of a star
condense down to about
the size of the Earth.
So that's still most of the.
A lot of the mass of the star
but a lot of the material
is now out stretched
out around the star.
And we can see from this.
It looks like it may be
pushed off in various waves
that it's not just one big
region that is expelled
but it does it at
various times, as you
can see various different
arcs and threw out the image.
Now, exactly how these
things are expelled out
is not something we
completely understand.
Obviously, it can happen
because we see it occurring.
But the physical mechanism
- What's actually going on?
There is something that is
not completely understood yet.
And there are various different
shapes of planetary nebulae.
So depending on the
exact conditions,
we can get variations they
don't all look exactly the same.
But there is a wide
variation in the structures
of the planetary nebulae
that we see out in space.
So that was our picture of
the day for December the 3rd
of 2019.
It was titled M27:
The Dumbbell Nebula.
We'll be back again tomorrow
for the next picture previewed
to be Electric Night.
So we'll see what that
is about tomorrow.
And until then have a
great day, everyone.
And I will see you in class.
