The Chandra X-ray observatory is celebrating 20 years in space this year, and oh, the things it has seen. Belinda Wilkes, who directs the telescopes operation, takes you on a dizzying visual tour of Chandra's universe.
Chandra: Two Decades of Seeing the Universe in a Different Light
Jeffery DelViscio, Kelso Harper
Jeffery DelViscio, Dominic Smith
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 among 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.