Claude R. Canizares at MIT – 2001 MA Space Grant Consortium Public Lecture

Claude R. Canizares at MIT – 2001 MA Space Grant Consortium Public Lecture


[MUSIC PLAYING] MODERATOR: This is an annual
Massachusetts thing that we do, is to bring in a distinguished
individual once per year to talk about activities within
various aspects of the space program. As you’re able to
see from the folder, we’ve had a very long
and distinguished group of the previous 11
speakers in this series. Our speaker this afternoon
didn’t have to travel very far. Professor Claude
Canizares has his office across the hall from
this meeting room, where he is the Director of
the Center for Space Research. Claude received all of
his education up the river at Harvard, has
been a leader here at MIT in the development of
what was earlier known as AXAF and now known as Chandra. It will be the subject
of his lecture today. He has been notable for
his government service and public service
in helping all of us in having our space
objectives realized. And among the many
things that he has done he has chaired the Space Studies
Board of the National Research Council. It’s my great privilege to
introduce Claude Canizares to speak about
“Probing the Violent Universe with the Chandra
X-ray Observatory.” Claude. CANIZARES: Thank you
very much, Larry. Well, I guess I have
to go on the air now. How does that work? Do you get some– do you get
some amplification back there? AUDIENCE: No. CANIZARES: No. Did the– did they
get turned on? Maybe the amplifier’s
isn’t turned on. Well, while we’re
working on that– I’m more instrumented
almost than the satellite you see in front of you. But the satellite’s
actually working well. No. AUDIENCE: You’re on. CANIZARES: Now I’m on. Oh, yeah, so I turned
the wrong switch. How’s that? Excellent. Well it’s a great
pleasure to be here and to have traveled so
far for this occasion. It’s also great because I
always enjoy talking about this. I have been having an
extraordinary amount of fun in the past year
and a half since Chandra was launched. And one of the things which
I regretfully will not be able to do
sufficiently is to mention the names of many of the people
in this room and a great many more who are not
in this room, who contributed to the things
I’m about to describe and made all this possible. One of the things that is a less
described pleasure of working in an area like space– science and space
research is the chance to work closely
with a great number of very dedicated and talented
engineers, scientists, managers, people
who bring together a lot of different
skills in order to make a project
like this happen. And so I want to
start with a tribute to them, even though I won’t
have a chance to mention them all as we go along. Well, the– what just
disappeared from the screen is the picture of Chandra. This is a large
satellite that was launched by NASA just a year
and a half ago, in July of ’99. And its purpose is to
join with the Hubble Space Telescope, the Compton Gamma
Ray Observatory, and shortly the Space Infrared
Telescope Facility in probing the universe with
the greatest possible precision. This observatory, in contrast
to the others that I mentioned, and the Hubble, which
is probably well known to most of you, has been
in the news a great deal, studies X-rays. And in studying X-rays,
we study the hottest and most violent
objects in the universe. And so what I’m
going to do today is to tell you a little
bit about the satellite and some significant fraction of
the scientific instrumentation, that was built, in fact, in
this building, and at MIT, and then another
part up the street, at the Smithsonian
Astrophysical Observatory. And then to give
you a little bit of a glimpse of
the kinds of things that we’ve been learning with
this remarkable new tool. First of all, a word
about X-rays, since I know that many of you are
very familiar, but some of you may be not so familiar with
fundamental properties. X-rays are, of
course, another kind of electromagnetic radiation,
but with wavelengths about a thousand times
shorter, and therefore energies per photon, or per
quantum, a thousand times higher than that
of visible light. And so having more energetic
quanta, more energetic photons, means that in order to
produce these X-rays you have to have some
object that’s somehow either very hot or very energetic. So if you take the
spectrum of radiation, of which visible
light, of course, is only a very small
piece in the middle, X-rays have a wavelength
of about, in our case, say 10 angstrom or 1
nanometer, and correspond to a temperature of
millions to hundreds of millions of degrees. And so that’s the kinds
of objects that we study. And, of course, in order to
learn about the universe, which is a vast place, and which gives
up its secrets only grudgingly, the goal in astronomy
and astrophysics for the last 40 years
has been to expand our grasp of this
electromagnetic spectrum as much as possible. And an important part of
that is this X-ray band that I will be
talking about today. Now, I can give you a
very close to home example of the difference between
studying things with X-rays and visible light. This is our familiar Sun,
the photosphere of the Sun. These days it’s more active
and has more spots on it. But otherwise, it’s a
fairly bland surface. And the visible
light that we see is generated by gas
at the temperature of the surface of the Sun, which
is the temperature of maybe 5,000 degrees, the
typical temperature of a reasonable flame. And that’s in a candle
or a Bunsen burner. And that’s why it
looks the same color. If you take the
exact same object and look at it with
an X-ray telescope, as was done first about 20 years
ago, and then more recently with a number of
satellite instruments, you see a very
different picture. This is the same Sun. And those two pictures were not
taken exactly the same time. But they could have been. And yet here what we
see now is material not of the temperature
of a candle flame, of thousands of degrees, but
at a temperature of millions, to 10 million degrees. And this is very hot gas,
confined in magnetic loops in the so-called solar
corona that extends way above the surface of the Sun. And so when we look
at the Sun in X-rays, we see a very different
set of phenomena. If we want to understand this
very energetic phenomena, then we have to look with
telescopes like Chandra. Now, why did I say that this
picture, and Chandra itself, is a satellite? And why do we go
to the difficulty, since the visible
light picture was taken from the Earth, of putting
our instruments in space? And, of course, the
reason is that the Earth’s atmospheric mantle
is extraordinarily opaque to X-rays,
which is probably a good thing for
us as human beings, but not such a good thing
for us as X-ray astronomers. So the only way we
can study these X-rays is to send our instruments
above the atmosphere. And this was done
first in about 1963, in a project led by then MIT
Professor Bruno Rossi, who many consider the father or maybe the
grandfather of X-ray astronomy. So we go up into space. And that’s what we do in
order to measure these X-rays. And the by far most precise
and largest instrument that’s been devised to do this
is the Chandra Observatory. Now, the Chandra Observatory
is an X-ray telescope. So it has something which
acts like a lens, which focuses X-rays, which are shown
here as little orange dots. It focuses X-rays from
a very distant source onto a sensitive detector
at the other end, and which will then
record the image. The key thing is
this telescope, which actually does the focusing. Now, focusing X-rays is an
extraordinarily difficult thing to do. And that’s one of the
reasons why this mission was so long in the making. X-rays are very penetrating. And if you shine it
straight into a mirror, they would simply absorb. And the only way to get
X-rays to bend sufficiently, to focus to a point, for
example, if they come from a point source in distance,
is to coax them very gradually to change their direction
by having them skip off a very highly polished surface,
much as a rock you can skip off the surface of a pond. Although if you threw it
straight into the pond, it would just go plump,
and through the surface. And so Chandra has four sets
of these highly polished nearly cylindrical surfaces. There’s a very slight
curvature to do the bending. And very highly
polished, in order to accomplish the focusing. And these mirrors were made
over a period of many years at an outfit which
is now Raytheon. But at the time this used
Danbury Optical Systems. And before that it was Perkin
Elmer, and which, guys, they made the Hubble mirror. So we had a lot of confidence
that this would be done right. [LAUGHTER] And you can see
here this polishing. This was really the
heart of getting Chandra to have its properties,
which I’ll mention in a moment. And just to give you an idea,
in order to make these mirrors, because you can see
you’re coming in at such a shallow
angle, you have to polish a great
deal of glass in order to get a relatively
small frontal projected area, collecting area,
to collect the X-rays. In fact, the effective
frontal area of this telescope is about a thousand
square centimeters. And yet we had to
polish something like 20 square meters
in order to get those 1,000 square centimeters
of projected effective area. The surface quality
is extraordinary. The average roughness
of the surface is three angstroms, which I
like to always make an analogy, that if you were to polish
the surface of the Earth to that precision, then
the equivalent bumpiness of the surface of the Earth
if we scaled these mirrors’ properties to the
Earth’s surface would be a few millimeters. So it’s an extraordinarily
well-done job. And they did it well. And it focused when
we got it onto orbit. The mirrors are then coated
with iridium, a heavy metal, in order to increase
the efficiency for bending these X-rays
at a glancing angle. And when were all done, the
telescope was assembled. This was actually
done by Eastman Kodak. Everything is done under
very clean conditions. In the space business,
it’s known that terrorists make excellent workers. And you can see they’re
already dressed for the job. And precision alignment–
and when we’re all done, the image quality that was
achieved with these mirrors is something like a half an arc
second, which is a factor of 10 better than had ever been
achieved with an X-ray telescope in the past. Well, the mirror, of course, is
just what focused the X-rays. Then there is a long tube. The whole focal length of these
mirrors is about 10 meters. So it’s an extraordinarily
large satellite. And the telescope
in this picture would go in the
front, fits in here, along with the spacecraft. And then in the back
are the instruments that detect the X-rays. And I’ll show you
those in a moment. Here’s the spacecraft portion. TRW was the prime contractor. And the final assembly was
in Redondo Beach, California, in their plant there. And this is the thing that has
the transmitters, and the power system, and so forth. The telescope fits in
the middle of this. And then the solar panels
stick out either side, to make the picture
that I showed you in the opening slide. At the focus, then we
have several instruments that can record the images. This one I’m
showing you here was one of the ones built here
at MIT, in collaboration with MIT Lincoln Lab. It’s the CCD detector. For those of you
know what that means, it’s charge-coupled
devices optimized for use in the X-ray band. And there are two rows of them. I won’t dwell on that. But these have been
developed in something like a 20-year effort, a
collaboration between George Ricker, and Mark
Bautz, and the people at Lincoln Lab, who have
optimized these for use with the X-rays. And they are an
extremely good detector. I’ll say more about
them as we go along. And then the other
instrument that was built here, largely
in this building, is one of these
two funny arrays. This one actually is the one
that came from a German/Dutch collaboration. The one built here at MIT is
slightly out of view here. These are periodic
nanostructures, which can be placed
behind the telescope. These are sort of
hinge structures. The telescope in this picture
is sitting, looking down on the floor below. It can be put behind
the telescope, to spread the X-rays
out in a spectrum. And I’ll show you an
example of how that works. And that’s the
collaboration, which I had with Mark
Schattenburg and Hank Smith over in electrical engineering
and computer science, to adapt the techniques of
large-scale integrated circuit fabrication to the
needs for our project. Well, finally, all these
pieces came together. It says, “Why It Took 15 Years
to Deploy the X-ray Telescope.” I didn’t tell you
that I was selected as a principal investigator
on Chandra in 1984. I daresay there’s some
people in this room that were barely alive at that stage. And for a long time I
called it Orwell’s curse because at that point
we were supposed to launch Chandra in 1991. And then the launch
slipped a year per year for the next eight years. And then finally it
stopped slipping. We did a lot of political
work and redesign work along the way. And, in fact, developed
even better instruments. But, finally, all those
pieces, all those players that I mentioned, under the
direction of Marshall Space Flight Center, which
was the center that directed this
effort, came together and we were ready to go. Chandra was loaded
into the Shuttle bay. Shuttle was the launch vehicle. After a lot of
discussion it turned out that that was the launch
vehicle of choice. And the size of
the telescope, here wrapped in its insulating
reflecting material, together with an extra rocket stage– because the Shuttle leaves
this in a very low orbit. And we wanted to end up
in a very high orbit– just fills the Shuttle bay. I mean, that’s not by accident. That was by design. And luckily, there were no
metric to English conversions that got in the way
of that activity. This was the Shuttle
launch in July of ’99. The first one commanded by
a woman commander, Eileen Collins, and included Cady
Coleman, who is an MIT alumna and also an alumna of the
University of Massachusetts. So if the Space Grant had
been around at that time, she probably would have been
supported by the Space Grant. And she’s the one who
actually pushed the button to get Chandra out
of the Shuttle bay. And so the astronauts
were ready. In fact, they were
ready three times. They loaded themselves in. And then there were two scrubs. And then finally,
on July 23 of ’99, the Shuttle took off
just after midnight. It was an extraordinarily
impressive sight. If any of you have not seen a
Shuttle launch, particularly a night launch, and are
in Florida at the time, I urge you to do it. It’s really extraordinary. It took off. Our little periodic
nanostructures were in there, being shaken to pieces. But not to pieces, it
turned out luckily. And then very
shortly afterwards, when Shuttle got on orbit,
they started the sequence to deploy Chandra. First, it’s on a hinged
system in the back. So that this thing, which used
to be lying in the Shuttle bay, is now already elevated
to the position at which it will be
gently pushed off just by mechanical springs
that were released. Cady Coleman issued the command. And Chandra was off. Here you can see the telescope. And here the so-called
inertial upper stage, which is the rocket that was
to take it to a final orbit. Shuttle backed away
a discreet distance. And that rocket was fired,
then a series of burnings. And it got it up to
its final orbit, which is a 64-hour orbit,
with an apogee of about 140,000 kilometers and a
perigee of around 12,000 or 14,000 kilometers. Here’s the crew, very happy
that they got this bomb out of the Shuttle bay I think. And they got their work done
very early in the mission. You can see that in Zero-G,
every day’s a bad hair day. But they were indeed very happy. And I have to say it was
a great pleasure working with these astronauts,
who were very dedicated to this task of
getting Chandra– were very excited about the scientific
implications of the job that they were doing in space. And came and visited us a
number of times beforehand, learned about the
mission, came afterwards to see how it was doing. And another part
of the privilege of working in these
space programs is to work with
people like this. Well, the operations– as
soon as the Shuttle bay doors were open, Chandra
was controlled from the control center,
which is just up the street. It’s in a rented
space in Draper Lab. This is the operations
control center. It’s the only control
center that can run Chandra. It’s the first time NASA has
allowed a major observatory of this class to be operated
entirely by an outside entity not under their direct control. And the Smithsonian
Astrophysical Observatory is the parent organization. MIT is also involved in
the Chandra Science Center, that helps run this activity. And the operations have
been extraordinarily smooth. Again, one of the
remarkable things is how well this has worked. Although I was just
informed earlier today that because of another
major solar flare, the satellite has
once again gone into a safe mode, which it
tends to do to protect itself when that happens. But other than that,
which are more acts of God than man-made, the operation
has been very, very good. So that brings us then
to what we’ve been doing for the last year and a half. Well, the first several
months, of course, we’re checking out
all the instruments, calibrating everything, doing
all the usual things one does, learning a little bit how to
operate it most efficiently. The operation now is
extremely efficient. Most of the actual available
time for doing science is spent doing
science, not doing other things, which isn’t
always the case with missions this complex. So now I’m going to shift
gears and stop telling you about the thing itself, and
rather the kinds of things that we’re learning. And this will be just
sort of a light overview of the kinds of
objects that we study, the way we use this tool to
probe the cosmic violence I talked about in the title. So I’ll start actually
with something which doesn’t appear so
violent, but is a place where, instead of stars dying, which
I’ll talk about in a moment, stars are born. And this is actually
a Hubble picture. And occasionally
along the way I will show optical pictures, as
well as the X-ray pictures, to help orient you. This is a well-known stellar
nursery in the constellation Orion, near the dagger
of Orion, which is about 2,000 light years away. And contains a lot
of dust and gas and new stars that are forming. Bright new stars that are
forming, many of which in this picture are
embedded and can’t be seen behind the dust and gas. That have condensed out
of this dust and gas and that are forming,
even as we speak. And some of them have formed
just within the last million years or so, which in
the lifetime of a star is a very short time indeed. Our Sun is about 5
billion years old. So that gives you a scale. The power of Chandra, I think
for me is best indicated by a picture like this one. This is a picture now,
not in visible light, but in X-rays,
taken with Chandra of the central part of this
Orion star-forming region. And it shows– this
sort of dark X-pattern that you see is just the
boundary between the four CTV chips. And you saw that in the
picture of the detector that I showed you earlier. But you can see a whole
collection of objects there, about a thousand
stars that are seen here shining in X-rays. The ones in the middle, they’re
so congested in this picture that they seem to all
form a single blob. In fact, that’s just the
limitations of the reproduction that I’m showing you. If you look at it
more carefully, as we have, in actually
a different picture, which takes care of
the overexposure, you can see many, many very
bright objects in the middle. Those are, indeed,
very massive stars. Many of these are relatively
low mass stars, that we think, like our Sun probably in
the early years of its life, were unusually active in
putting out X-rays of the kind that I showed you on
the Sun now, but were a much larger part of the energy
output in those early days. There also objects here, which
we think are just starting, haven’t even turned into
fully formed stars yet, that are also, for reasons that
are not well understood, putting a remarkable
amount of their energy into X-ray production. And so this is an area– this
is a very active study of how this, via this so-called
violence that happens in the heating the material
to very high temperatures in the corona, coexists with the
other formation processes that are going on in the source. Now, whoops– well– I think I really
like this picture. Whoops– we went to
sleep for a moment. We’ll get back to– there we are. All right, so much
for stellar birth. Let’s go to stellar death. That’s always more fun. A lot of the things
that we study have to do with the
products of what happens not at the beginning of
a star’s life, but at its end. This shows a visible
light picture of a piece of the sky in the
constellation Cassiopeia, which has been
known for many years to be the remnant of
a supernova explosion. A star that ended its life in
a cataclysmic explosion, which we think is not at all
uncommon way for stars to die and which was probably
seen by the astronomer Flamsteed about 350 years
ago and recorded visibly as a bright object in the sky. The thing that’s interesting
from the point of view of astrophysics is, this
little debris here is the remnants of the explosion. All the other dots
are just normal stars. And this is a visible light
picture again, remember. And so this is just
little wispy stuff, which is a small amount
of debris which came out of the inside of the star. Now, there are a number of
reasons why these explosions are of interest. But one of the things
that interest me a lot and some of my
colleagues is the fact that these are the
sources, these supernovae are the sources of
all the chemical elements that are of
interest to us, other than hydrogen and helium. In the early universe
there was virtually nothing but hydrogen and helium. And all of the carbon, nitrogen,
oxygen, silicon, sulfur, et cetera, et cetera,
had to come out of the nucleosynthetic
furnaces inside a star and then be ejected, so that it
could mix with other material to form things
like planet Earth. Otherwise those elements
simply wouldn’t be there. So one of the things
we like to study is the material that comes
out of the supernova explosion because that’s a unique
opportunity to see stuff, just as the star obligingly
turned itself inside out to allow you to look inside
and see the material there before it disperses so
broadly in the galaxy that it’s no longer visible. I should say that this
object is about 5,000, 6,000 light years away. And it’s about 10
light years across. That gives you a
scale, this ring. Now, it turns out these things
are absolutely ideal objects for study in the X-ray. Here’s the Chandra image
of exactly that same ring, that same piece of the sky. And now, instead of
seeing a few wisps– it still looks wispy. But I can tell you that by
adding up all the material here, we can see the bulk of
this material that came out of the star in the
center when it exploded is seen in this picture. Now, heat it up to temperatures
of about 10 million degrees by the shock that it
encounters as it flies out from the initial explosion. And the initial
explosion sends out the material at velocities
of about 5,000 kilometers per second. So it’s moving. And when it runs
into stuff around it, it gets heated to these
very high temperatures. Now, one of the things
that is of great interest, as I just said, was to study the
chemical composition of this. And the cameras that
were built for Chandra give us really the
opportunity to do that. The X-rays that come
out have energies which are very characteristic
of the element that’s emitting the X-ray. So that you can actually
do a chemical analysis by looking at the wavelength,
the precise wavelength of the X-ray, or,
as it’s depicted in this picture, the color. And I should say that the
previous slide, the color was just used to
indicate the intensity. Here is one case where the color
is used to actually indicate the energy of the X-ray. And I can tell you, for example,
that these red blobs over here are almost pure iron
that was ejected from the interior
of the supernova, and that are flying out. And then there are others
that are heavily enriched with silicon and sulphur. So we’re actually
seeing the elements that were synthesized in the
interior of the star and are now being ejected. And one can do an
analysis of those. I should say that this
was a very massive star. It was probably about 20
times the mass of the Sun before it exploded. So there’s a lot
of material there. And I’ll be talking about– say another word
about those kinds of stars in the next picture. Whoops– did I skip over–
no, I guess I didn’t. This is another case of
such a supernova remnant. Here it is, this ring. Now, this one actually looks
smaller in this picture. And it appears
smaller on the sky. But it’s actually larger
in linear dimensions because it’s much further away. But it’s similarly the
ring that’s left over. This is, again, another
Chandra picture. I’ll tell you about this
rainbow in a moment. Just look at this
part for a second. This is, again, a picture
of the stellar debris that is flying out from an
explosion, thought now to be about a thousand years
in the past, instead of 350, as I showed you before. But again, it is the supernova
from a very massive star. This is just much farther away. This is about 150,000
light years away, in actually a very small
neighbor galaxy of ours called the Small Magellanic Cloud. Now, I mentioned the other
instrument that was built here at MIT is these little
devices, that when put in the beam spread the
X-rays out in all their colors. And in this display,
where we’ve also used the color of the display
to emphasize that point, you can see little images
of the supernova remnant, but displaced. And exactly where
they fall depends on the wavelength of the X-ray
that’s dominating the emission. And you can see from
the labels up above that each one of those
rings corresponds to a different element. So with this instrument, we
can go along and actually measure independently the
location in this supernova remnant of neon, or
magnesium, or oxygen. And really do not just
a chemical analysis, but a detailed spatial
analysis of the material. And that, for example,
gives us a picture of in this case, only
oxygen, where oxygen was emitted in this explosion. And I said this was a
fairly massive star. This may even been more
massive than the previous one, but say 20 or so
solar masses of star. It managed to turn
itself into probably somewhere between three and five
solar masses of oxygen alone. And it is these stars, which are
relatively rare in the galaxy, but which, when they
explode, provide the bulk of the oxygen
that enriches the universe. And so they’re particularly
of interest to those of us who think oxygen is a useful thing. So when you take
your next breath, you’ll be breathing actually the
piece of a supernova remnant. Luckily, it’s
cooled down by now. And to give you a
scale, our solar system has only a tiny fraction of
a solar mass worth of oxygen. There’s enough oxygen coming
out in this explosion to seed, once it’s finally mixed
with other elements, some many thousands
worth of solar systems with the same amount of
oxygen that we have in ours. So they’re real stellar
warehouses, if you like, of oxygen. One of the other
things that we can do with this very fine
spectral information is to actually look for
velocity information as well, using the
well-known Doppler shift, which shifts
very slightly the wavelength of the lines. And so this picture
shows that remnant. And the arrows on top of it
are to indicate the velocities that we can measure
around this ring. The red ones indicate
velocities away from us, so-called redshift. And these would be blueshifts,
velocities towards us. And the scale is
such that this arrow corresponds to a velocity
of about 2,000 kilometers per second. So now we not only see the
elements that are coming out, but we can actually measure
the velocity of ejection from the original explosion
and measure its energy. The total amount
of energy that’s released by the way in one
of these supernova explosions is very considerable. It’s 10 to the 51
ergs, for those of you who are work in CGS
units, the way we do, which is comparable to
the amount of energy that the Sun puts
out on a daily basis if you add up that
total over almost the full lifetime of the Sun. So it’s a very large amount
of energy that gets put out. And that’s what we’re
trying to measure. Now, those of you who saw
this picture earlier probably noticed something which
I neglected to mention, that little dot in the middle. And one of the other interesting
aspects– in fact, this was actually our so-called
first light picture. This is the first
astronomical object that we pointed Chandra at. And as soon as it
came up on the screen, all the astronomers in the
room focused on this thing because this hadn’t been seen
before because the previous images simply didn’t–
you know, were too blurry. They were blurrier than this. And this just looked like
another blurry thing, like that little blurry
blob or that blurry blob. But when you have
very sharp focus, it turns out that that’s
effectively a point. For years people
have been wondering about what happens– in
this particular case, what happened to the
very central part of the star that exploded,
to give rise to this debris? It’s been known,
again for many years, that these supernova
explosions are not only the origin of
the chemical elements in the universe,
but also the origin of very collapsed central
objects, the central core of the star which collapses
gravitationally, and is what actually drives the
explosion of the outer part. And which are
either neutron stars or the ultimate collapsed
object, black holes. It was a puzzle why this
object didn’t have one. And the answer is
simply it does have one, but it wasn’t
clearly seen before. So one of the interesting
objects of study in X-ray astronomy is now not– now, I’m switching from
the study of the debris to the question about
the nature and properties of these highly collapsed
objects, neutron stars or black holes. Neutron stars are
stars with a mass comparable to that of the Sun,
but the dimensions of the city limits of Boston. So it’s extraordinarily dense. They have densities of the
nucleus of an atom, which I actually set on my
calculator to convert, is about 100 million tons
per cubic centimeter. And because of
their great density, they often have very energetic
phenomena associated with them, either because material
is falling into them, because they’re
spinning rapidly. Their great mass
density often translates into other energetic phenomena. And so they are very
interesting objects for the study of X-rays. And– I’ve got so many
instruments here I can’t keep track of them. Sometimes these collapsed
objects, either neutron stars or black holes, are formed
in a supernova explosion, in which the star that gave
rise to that has a companion. And the companion could be
a relatively normal star. By the way, I said that
Chandra has very good angular resolution. But it wasn’t good enough
to take this picture. This is an artist’s conception. This is a normal star– and it also doesn’t
show the X-rays. There’s these funny
little wiggly lines– in which the companion is one
of these very collapsed stars. It’s so collapsed
that as material is pulled off this companion
star and falls down, and down, and down, and down, seemingly
forever, until it hits– or disappears into
the black hole, at the center there’s an
enormous amount of energy released, more than you would
get from nuclear fusion, for example, if you could
just fuse all that stuff in a reactor. So there’s a great
deal of energy emitted. And that energy comes
out primarily as X-rays. And so these are
objects of which there’s a lot of interest,
in which we can learn a lot, both about the objects
and about how they interact with their companions,
by looking in Chandra. Here is just a picture of
one of these in our galaxy. And you can see some of the
streaks here from the spectrum that I– because this picture was
taken with the spectrometers in place. And there’s a lot to be learned,
but more than I can tell you in the short time. So instead, I’m going to move
to a larger scale, where you’ll see these same kinds of objects,
but now in greater numbers and from a greater distance. This is an entire
galaxy of stars. And this one is a
particularly active galaxy. It’s a galaxy that’s now
outside of our Milky Way, which, of course, is our own galaxy,
at a distance of about 10 million light years. And this is a visible
light picture. So you see a lot of stars. These bright stars
are in our galaxy. We’re looking
through, of course, the stars in our galaxy, to
see the more distant one. And this looks a little funny. It’s disturbed. It’s also– well, there are
limitations of the PowerPoint resolution as well here, too. But you can see
these dust lanes. This is an area in which there’s
a great deal of stellar birth and stellar death going
on simultaneously. There’s a burst of activity. When you look at
it with Chandra, you see sort of an
ensemble of things that are the same
kinds of things I’ve just been describing,
but now seeing all altogether. There’s a lot of diffuse gas,
this stuff blown out here. And this is because there’s
so much stellar birth and stellar death going on here
that many, many supernovae went off, more or less
all at the same time. And have blown out
the whole inner part of the gas in this galaxy. And then you see these
very bright objects, which are, in fact, X-ray
binaries of the kind I just described, in which there
is a collapsed remnant of a supernova that is
accreting material and glowing very brightly in X-rays. And this is the our
neighbor galaxy Andromeda, which is a little bit closer. It’s a couple of million
light years away. And this is again a
visible light image. And you see all the stars. A galaxy like this,
and like our Milky Way, has maybe something like
100 billion stars in it. And the very center
was imaged by Chandra. This little dark
box here indicates the part in the picture
I’m about to show you. And there, again,
we see this evidence for both some
diffuse gas, but also these very bright X-ray
binaries of the kind that I’ve been describing. But the center of this galaxy– and, in fact, we believe the
centers of every galaxy– has another kind
of object as well. And shown here as a
blue dot because it has a different X-ray color. And these objects, in
contrast to the sort of stellar-sized objects I’ve
been talking about so far, are very massive
black holes, which are formed from the
accumulation of debris from all the stars, over
the lifetime of the galaxy, collecting down in the
very center of the galaxy, the lowest point, if you like,
in the gravitational potential, where this debris collects and
eventually collapsed to form a very massive black hole. In this case, in the case
of our neighbor Andromeda, something– maybe
around 100 million times the mass of the Sun. But in other cases,
up to a billion or even 10 billion times
the mass of the Sun. Now, these objects
themselves are really fascinating in their own right. They are the largest black
holes that we know about, as I say up to 10 million– I’m sorry, 10
billion solar masses. And they cause a remarkable
amount of disruption in their neighborhoods. The force of gravity is so
strong here that material, as it falls in,
again it releases a great deal of energy. Processes that we don’t
entirely understand, which I’ll show you in a moment,
that as the stuff spirals in, some of it is actually
squirted out again in extremely
energetic jets, where the material is
traveling very, very close to the speed of light. So these objects are may be,
in terms of single objects, among the densest, most
energetic in the universe. And, of course, therefore
are prime objects for study with Chandra. Here’s the center of our
own galaxy, by the way. And this work is also
being done here at MIT. This is an image of the
center of our galaxy. And it looks kind of like
that stellar birth/death case I was describing before. This is a region that’s maybe
several tens of light years across in the center
of our galaxy. There’s a fair amount
of activity going on, not nearly as much as
in the active galaxy I showed you before. But all these dots are
probably X-ray binaries. And the general diffuse
gas that you see here is mainly left over from
supernova explosions. And there is one
dot there, which is the massive black
hole that’s in the center of our own galaxy, which
is actually remarkably quiet as an X-ray source
compared to some of the others that we know. But is a very interesting
one because it’s our own. And we feel a certain
ownership of it, right. Here’s a case where we
can actually see some of this energetic activity. This is another kind
of disturbed galaxy. This is a galaxy which, again,
has been known for some time to have a lot of activity
associated with it. This is a visible
light picture again. The dust lane indicates that
probably maybe a smaller galaxy was swallowed up, fell
into the large one and was stripped of its dust. And that may have triggered
some of the activity. This galaxy is about 10
million light years away. And this picture
is probably about– from here to here might be
tens of thousands of light years or so. Now, when we look at it with
Chanda, at this same picture– and it’s roughly the same
scale– this is what we see. Well, you can see the
scale because actually this is a superposition. This is the optical picture seen
in sort of bluish-white light, with a dust lane. And the red is the
Chandra picture. And you can see sort of shining
through, without any doubt, is a very strong X-ray
source right in the center. That is the massive
black hole that sits at the center of this galaxy. And you can see this long
squirt of material coming out. This is one of those ejections,
jets as they’re called, of very energetic particles. And the fact that they glow in
X-ray, even tens of thousands of light years away
from the center, and that it’s well collimated
in a squirt is one of the things that we’re trying to understand. What are the energetic processes
that actually transport this large amount of
energy so efficiently out such large distances
from the central object? And then what can
we learn, of course, about the central black
hole in the middle? Now, when these things
are farther away, and more locally–
this is actually– I say it’s very energetic. But this is relatively
puny, to the most energetic of these
objects, which are called quasars, which is cases where
this same activity is going on presumably in the
center of the galaxy, but now at much greater
distances and much larger energies. But before I get
to the quasars, I’m going to talk about yet
another kind of phenomenon, where Chandra has helped us
understand what’s going on. This is an optical picture,
actually from Hubble, of a cluster of galaxies. So far I’ve been talking
about individual galaxies, with their 100 billion stars. Now, I’m talking
about whole clusters of thousands of such galaxies. And this is an example of one. These are found scattered
throughout the universe. They are the largest
gravitationally bound objects in a universe, in which
thousands of these galaxies are close enough to swarm around
and form a gravitationally bound system. Typical dimensions go up
to millions of light years, a few million light years. In this case, this is only the
very central portion, maybe only a few hundred thousand
light years across. Now, what we see here
are all the visible stars in the individual galaxies,
the hard dots rather. There are a few foreground
stars that always creep into a picture like this. But anything that’s
fuzzy is a distant galaxy that’s part of this cluster. When we look at such a cluster
of galaxies with the X-rays, we see a very different
picture again. Now, instead of the
individual galaxies, for the most part,
what we see is a glow of a very diffuse
region of hot gas that’s spread throughout the
space in between these galaxies and which actually contains
more matter than all the stars and all the
galaxies in the first place. Now, I’ll give you
just one example of one of the things we’re learning. This is a poor picture of
another cluster of galaxies. I showed the last one because
it’s much more dramatic. But you can see a couple of
galaxies here and then a lot of other fuzzy dots. So this is a poor reproduction. But the reason that
this is interesting, and one of the things that
we’re just now revealing with Chandra, is that these
things, although they’re gravitationally bound, are
still in the process of forming. And in this case, for example– I’m about to show you
the Chandra picture– these are actually
two smaller clusters that have just
collided and started passing through each other. And we can see that
in the next picture. And I’ll show you
when it reveals that. This is basically the
same piece of the sky, but now seen with
an X-ray telescope. You see a diffuse glow from
this very thin, hot gas that spreads between all
the galaxies in the cluster. And these rather sharp edges– we can actually measure the
temperature and the pressure jump across the edges. These rather sharp edges
are indicative of the fact that there– and this elongation
is indicative of the fact that they are really two blobs
of gas that have just finished merging, and one
cooler than the other, passing through each other. So the dynamics of how
these galaxy clusters formed is suddenly revealing
itself in by means of these X-ray pictures. Now, the last thing
I’ll talk about is pushing to the edge of
the universe, which is always a good thing to do, particularly
if you want to get headlines. And it’s also a good thing
to do because it really helps us understand the sort
of evolution of processes in the universe, from the
earliest times to the present, and how the current universe
that we live in and see around us locally came to be
from the Big Bang itself. This is a Hubble picture, a
well-known Hubble picture. It’s on the wall over
here to the left, in case you want to look
at it more carefully later. A beautiful picture,
that was done by pointing Hubble at
one point to the sky and exposing the detectors
on Hubble for about a week. And it was a piece
of the sky that where there was nothing particularly
bright or interesting going on. And what it revealed,
almost as if you know when you look at
a little drop of water under a microscope, is a teeming
life of galaxies, all of which, at all distances out to the
most distant galaxies that can be detected by present means. Chandra did the same thing. Chandra’s field of view
is actually a lot bigger. So its picture is
much, much bigger. But in this exact
same piece of sky, Chandra also looked
for roughly a week, and to try to find
out what was there. And these results are
only just now coming out. This was given to me by our
colleagues at Penn State. Here’s a picture of just that
piece of the sky, the Chandra image. And now you can see only
certain ones of these objects are hot enough or
energetic enough to glow brightly in X-ray. Each one of these is
something different. Some of them have
already been identified as supermassive black
holes of the kind I’ve just been talking about,
quasars that lurk in the hearts of
massive galaxies. Others appear to be
relatively normal galaxies, that we wouldn’t
have thought have some kind of energetic
phenomena at the center. But when you looked with
X-rays, you find that they are. And this is something which
just now people are starting to be able to do, to push to the
largest distances, the highest energies, and figure out what
in this variety of objects that you see in a visible
picture can tell us about the energetic
processes in the universe that we see in X-rays. Well, Chandra is itself– whoops, I went too far. Why does it keep doing that? Chandra is itself an
astronomical object. This is a picture taken by an
amateur astronomer in Alabama shortly after the
Chandra launch. And you can see this
little streak here, is Chandra moving across the
sky during the time it took for him to expose this picture. I don’t remember
how long that was. And it’s in a very high
orbit, as I indicated, which will last,
at least 50 years, if anybody’s done the
calculation of perturbations on the orbit. The design life of
Chandra is five years. But we have no reason to believe
it shouldn’t last at least 10. And NASA has obligingly put
in enough funding for us to operate it for
10 years at least. We have every reason
to believe it’s going to continue to be
as functioning as well, because the engineers here and
elsewhere did such a good job building it. And returning as many exciting
results, as we’ve just had a chance to glimpse so far. In fact, I have a
feeling right now, myself, of having kind
of walked into a banquet, with a huge smorgasbord table. And I’ve just gotten through
the first few appetizers. And although I feel
like I’m already full, I just can’t wait to get
onto the main course. The results from this
mission are really, I think, going to change a lot
of what we know and think we know about the universe. There will be more
surprises to come. The one surprise that– I used to tell
people before launch that the one thing that
would surprise me most would be if Chandra didn’t
give us any surprises. And I think already from
what we can see I’m not going to be disappointed. Thank you very much. [APPLAUSE] I’m happy to take
some questions. Tom, could you flip the switch? Thanks. MODERATOR: Questions for Claude,
as the entire universe is open with the subject matter? AUDIENCE: What
are exposure times for the large-scale
photographs that you’re taking. CANIZARES: Exposure times,
what are the exposure times for these images? They range for–
probably the shortest would be about 20 minutes. And the longest ones so
far are a week to 10 days. Those we can’t do too
many of, obviously. More typically,
they may go for– hours would be sort of probably
the median observation. These X-rays arrive very slowly. For a lot of sources
that we’re detecting, the rate of the
actual photon arrival is fractions of
photons per second. So a photon every 10 seconds
would be a pretty good deal in our business. AUDIENCE: The jet you showed
coming out of the black hole was in one direction. CANIZARES: Yes. AUDIENCE: Is that related to the
angular momentum or something? Or do they come in both
directions sometimes? CANIZARES: It’s thought
that usually they come in both directions. In that one, the study of the
counter-jet, if there is one, has been kind of interesting. It looks like there is something
going in the other direction. Some of that could well
be a selection based on so-called Doppler boosting. I mean, if you’re seeing– you get a enhanced– the relativistic effect is such
you get an enhanced emission along the direction. And a lot of the jets that
are seen in this business, many of which were– all of which were first
detected in the radio part of the spectrum, where you’re
looking at the synchrotron radiation of these electrons. And you’re probably
seeing just the ones that are boosted because they’re
beamed in a forward direction. It’s probably a beaming
effect for the most part. But there may be some
where for some reason it really is lopsided. AUDIENCE: Are these events
related to cosmic rays as far you know? CANIZARES: Are these
related to cosmic rays? They may be. I mean, it’s thought
right now that most of the cosmic rays
that we see probably come from things like
supernovae explosions. Although now people are
talking about very energetic cosmic rays may come from
gamma ray bursts or something like that. Whether active galaxies
generate a significant number of cosmic rays, I’m not sure. There are probably some
who hold that they do. But I don’t know that there’s
any firm evidence of that fact yet. Tony? AUDIENCE: Can you
detect emissions from really heavy elements. CANIZARES: Can we
detect emissions from really heavy elements? We actually– first
of all, it turns out that mainly what we’re seeing
are the most cosmically abundant elements. As I say, the signals
are fairly weak. And so we see things
up to iron, maybe some indication of nickel. Heavier elements are
produced presumably in the explosion themselves. They’re synthesized during
the supernova explosions. And they may be there. But they probably are
there in such small numbers that we wouldn’t have
expected to see them yet. And then you also
have to find ones that have characteristic
lines, right in our part of the spectrum. So my guess is that
we’re not going to be able to say too much
about the heaviest elements. There is a mission going up
soon, a European mission, called INTEGRAL, which actually
should have the ability to detect higher
energy gamma ray lines from heavier elements. It may be closer in on
our galaxy at least. But then we’d see some
of the heavier elements. AUDIENCE: I’m going to
ask another question. What about the state of
ionization [INAUDIBLE] CANIZARES: I didn’t
mention that. But the question is, what
about the state of ionization? We are seeing these elements,
say nitrogen through iron, in very high states
of ionization. Other than iron, most
of what we’re seeing are in the either hydrogen-like
or helium-like state. In other words, it’s
oxygen, with all but one or all but two
electrons stripped off. Iron we see in a
variety of states. But typically, at
least 10 electrons have already been stripped off. At these temperatures,
that’s the equilibrium value for those ions. AUDIENCE: [INAUDIBLE] CANIZARES: That’s correct. And in the
astronomer’s notation, in which oxygen 8 means oxygen
plus 7, if you’re a physicist. AUDIENCE: You indicated
at least one example at the end, and
others earlier, where Chandra had followed
observations that Hubble had
taken in the visible, with a good synergy
between them. Have you started to see examples
in the other direction yet? Or is it too early? CANIZARES: No, we have. I mean, people
have proposed to do Hubble observations to
make sense of their Chandra observations. And, in fact, right now, in an
extraordinarily co-operative move between the
two observatories, they’re actually
when you propose– it’s possible to
send in one proposal to do simultaneous or
contemporaneous Chandra and Hubble observations. So there is a desire to make
the most of these observatories in those cases where that’s
a useful thing to do. AUDIENCE: You
mentioned that there is more mass in the
dust in the cluster than in the galaxies themselves,
if I understood it correctly. CANIZARES: Yes. AUDIENCE: Could the missing
part of the universe be in that form? Is this in a plasma state? CANIZARES: Yeah. So the question is, could
this gas in clusters be something about the missing– what is its relation to the
missing mass in the universe? It is in a plasma state. It’s a hot plasma, at typically
30 to 100 million degrees. And it’s enriched
with heavy elements, not as much as in the Sun. About a third as much as what
we see in the solar system or in the galaxy. But it is not anywhere
near enough to provide the so-called missing
mass in the universe. In fact, it is very
useful because since these are the largest gravitationally
bound objects in the universe, they probably have an
appropriate– they probably have a mix of normal
matter, baryons, and dark matter, that’s
similar to the average in the universe as a whole. And all the models
seem to indicate, and theory seem to indicate
that that’s the case. And so what we see is that
all the normal matter, including the X-ray gas, which
is typically three times what you see in the stars,
three or more times what you see in the stars. So almost all the normal
matter is in X-ray plasma. And then there’s
the dark matter. Because the gravity
that you deduce from the motions of
this– in fact, just to confine the hot
gas itself, requires another, almost 10
times more material. And so that’s where this
statement comes, that there still has to be dark matter. So, in fact, studying
that X-ray gas is probably the best
way to really deduce how much dark matter
there has to be. MODERATOR: In closing, let
me offer you this certificate of appreciation. CANIZARES: Oh, thank you. MODERATOR: Best use of
the spacecraft consortium. And thanks not only to you,
but to all of our colleagues who made this possible. It’s extraordinary. CANIZARES: Thank you very much. [APPLAUSE]

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