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
January the 19th of 2020.
Well, it is titled M1: The
Incredible Expanding Crab
Nebula.
So what is the Crab Nebula?
Well, this is an example
of a supernova remnant
visible in the
constellation of Taurus
and it was actually seen
to explode as a supernova
here on Earth in the year 1054.
So nearly 1,000 years ago.
And since that time, it
has been watched to expand.
So images taken of
it at various times
we can actually measure the
expansion at an incredibly
fast rate.
And if you think about that
1,000 kilometers per second.
So every second it gets
1,000 kilometers bigger.
However, if you look
at the Crab Nebula
just individually you
will never see it expand.
You have to look at
over a yearly time spans
to be able to see the changes.
And that is because even
though it's moving it
the parts are moving 1,000
kilometers per second,
it is also thousands
of light years away.
So the fact that it
is so far away also
means that we're
not going to see
it expand or see
it appear to move
as fast as we would otherwise.
Now, this is actually
a short time lapse
video that you can watch
and when you play it,
you will see the expansion.
And you can watch
towards the center,
especially and see material
that is still expanding out.
Now, if you look,
this takes place
between the years 2008 and
2017 so over about a decade.
So that's about 10 years
worth of expansion.
And we can still
see the shockwaves
moving outward from this
incredibly intense supernova
explosion.
One of the most violent events
that can occur in the universe
when a star at the end
of its life will explode
and we can see how large this
is that over that 1,000 years,
it has expanded out
and become a very large
object actually about
10 light years across.
So it has become very
large over that time.
And as we can see
clearly visible
with in the
constellation of Taurus
and we can study this
remnant of a supernova.
Now supernovae are
important because this
is what produces a
lot of the heavier
elements in the universe.
The original big bang created
hydrogen and helium only so
a lot of the other
elements in our body.
And here on the Earth were
not created at that time.
It took can creation
within have massive stars.
And then these explosions
to expel heavier elements
backed out into the universe.
So things like iron and gold
and tin and other heavy elements
need to be expelled back
out into the universe
to be able to form planets
like the earth that
have a lot of carbon
say a carbon and silicon
and iron in them as
well as life forms
as well that contain those
heavier elements watch
too an astronomer is anything
other than hydrogen or helium.
So here we see an example of one
of those supernovae in the Crab
Nebula and get to watch
it expand a little bit
over the last decade or so.
So that was our picture of
the day for January the 19th
of 2020.
It was titled M1: The Incredible
Expanding Crab Nebula.
We'll be back again tomorrow
for the next picture previewed
to be Meteors Through Orion.
So we'll see what that
is about tomorrow.
And until then have a
great day, everyone.
And I will see you in class.
