I'm Belinda Wilkes and I'm the director of NASA's Chandra x-ray Observatory
which is the world's premier x-ray telescope
and I'm standing in the Dome of the Great Refractor at Harvard College Observatory
and at one point was the largest telescope in the world.
It was looking at the stars in optical light. Chandra looks at the stars in x-ray light.
So looking at telescope above us it's 10 meters long it's as big as a
school bus and at the front end the x-rays come in from a celestial object a
long way away and they hit the mirrors first the mirrors are spherical shells
and the light comes in at a very small angle and then just to reflects at a
grazing incidence off two different mirrors and then goes the whole length
of the telescope to the detectors at the far end 10 meters away.
So the surface of the mirror has to be accurate within the level of a few atoms,
so these are the smoothest mirrors that have ever been made.
The official first light image of the Chandra x-ray Observatory
was the supernova remnant Cassiopeia A.
And it exploded about 350 years ago and is expanded ever since.
It's now about 30 light years across.
A supernova remnant is the result of a massive star blowing
up as a supernova when it runs out of fuel in its core and then the debris
gets blown out and keeps expanding into space.
The supernova actually shines brighter than all the stars in its galaxy which
is about a hundred billion stars for a couple of days so it's incredibly
energetic phenomenon and since all the heavy elements in the universe beyond
hydrogen and helium are formed in the middle of massive stars this is actually
the place where those elements can be distributed into space and can
eventually be formed into a next generation of stars with perhaps planets
around them with perhaps people on them like ourselves because the elements in
our body were actually born in the middle of a massive star.
The debris itself tells us a lot about how the star originally exploded.
First of all, we can look at where the individual elements are in the star.
Iron would have been in the core of the star before it blew up but it's actually in the outer
parts of the debris so the star in some sense blew inside out but also there was
likely to be iron generated in that explosion as well.
Most of the sources we see with Chandra are black holes of some kind.
There are stellar-mass black holes and then there are supermassive black holes
that we find in the cause of galaxies these are actually very small but
incredibly massive they're the most massive objects in the universe and in
the middle of a galaxy the supermassive black hole is about as heavy as a
million or even sometimes a billion suns.
The nearest one outside of our galaxy is
in a big galaxy in the center of a cluster that's called M87 or Messier 87.
Chandra sees the very hot material from the accretion disk around the
supermassive black hole and since x-rays come from the hottest material so this
is tens of millions of Kelvin these x-rays are probably formed very close to
the edge of the supermassive black hole.
Clusters of galaxies have a large amount of hot gas in them that can only be seen in x-ray wavelengths.
The x-ray gas in the middle of clusters is actually not smooth and boring but in fact has a lot
of structure in it.
We see sweeping cold fronts, and we also
see voids sort of holes in the x-ray gas and shockfronts, bright shockfronts on
the outer side of those holes and these are generated from that supermassive
black hole right down in the core of the galaxy so the structures are actually
giving us a fossil record of all the outbursts from that supermassive black
hole in the core over the lifetime of this cluster
The galaxy in which we live the Milky Way galaxy is a spiral galaxy which
actually means it's flattened and if you could look at it from the top has a
bunch of spiral arms they're really very pretty but we can't see the whole thing
at once but there are many spiral galaxies in the universe that we can see.
The galaxy or pair of galaxies that we're looking at now M51
also known as the Whirlpool is a classic face on spiral galaxy with
beautiful spiral arms. The difference with this one is that it has another
little spiral next to it and it's interacting with that spiral.
So most of what we see in the galaxy if we look in optical light is stars that are on our
side of the galaxy and gas and dust that's hot enough to shine and then
there'll be dust lanes that block our view. If we look in the x-rays we can
actually look all the way through the galaxy and we can actually pinpoint very
young stars young stars are bright in the x-rays so we can see them even
amongst the gas and dust because they're emitting x-rays. We also see binary stars
we often get a star that has the mass of about the Sun in a binary system with
a neutron star or sometimes a stellar mass black hole. And they move around
each other and because of that they interact and they shine in the x-rays
with the accretion disk very like a supermassive black hole but on a smaller scale.
So we see in this particular galaxy about 400 x-ray emitting stars
most of them will be binary stars.
So they do tend to form in star forming regions
and as you can see in this picture they really outline the arms the
spiral arms of the galaxy.
As human beings we've always been curious about
the things around us. We want to explore our world.
We wonder what those planets are and what the specks of light in the sky above us.
So to that quest of astronomy if you like humankind in terms of looking at the universe
x-ray brings a new dimension of the hottest material the most energetic
particles around magnetic fields the places where the atoms that are in our
bodies were made and how they actually move out into the galaxy around them and
perhaps eventually make new generations of human beings or other kinds of life.
So it's only by looking out in the universe that we're going to understand
these things and be able to put ourselves in the context of the universe
and science as a whole.
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