The World Around Us- Ned Wright Zeitgeist Americas 2012


Uploaded by zeitgeistminds on 15.10.2012

Transcript:
>>Ned Wright: When I was studying astronomer, we had a picture
of the sky, and it's now clicked too far, so can we back up?
Eventually, we'll back up. But the -- you know, while I'm up here -- there
we are -- you see this astronomer holding up the glass plate. Our view of the sky was
the Palomar sky survey, which was taken on 14-inch glass plates, of which about 1200
covered the whole sky. And there was one copy in the red and one in the blue and these were
reproduced on photographic paper and distributed to all the astronomy departments and observatories
around the world, and this is how we knew what was in the sky.
But I wanted to do this in the infrared. Now, the infrared is a different wavelength range
than the optical, and so you can see my picture on the right in the infrared, that it's really
light that comes from the radiation of ordinary objects at room temperature, or people. So
it's really telling you how hot things are. And this is a very different piece of information.
And it's actually very important for a number of studies, but one of which is, how big are
asteroids. So we're a little bit worried about asteroids
hitting the Earth and wiping out the dinosaurs or maybe something else. But asteroids actually
come in a wide range of colors, from very dark charcoal gray to a very white, chalky
white. And so if you see an asteroid with a telescope, like in the upper left, you don't
have enough resolution to actually see how big it is. And so you can only go by how much
light it reflects. And these two asteroids, one big and dark and one small and light,
reflect the same amount of light. But if you look in the infrared, the dark one is hotter,
because black things get hotter in the sun. And so it radiates a lot more radiation. So
with an infrared observation, you're actually primarily sensitive to the size of an asteroid.
And so this is very important information. So in order to do an infrared study, because
room temperature objects radiate infrared, we can't have a room temperature telescope.
So we need to keep the telescope very cold. And in order to do that, we have to keep the
telescope up above the Earth's atmosphere, which is also room temperature and radiates
infrared. But even more important, it would freeze on the cold telescope. So you could
freeze the air onto the telescope. And this was done by the wide field infrared survey
explorer, shown here in a computer-generated diagram. And this has mapped the entire sky
in the infrared. Now, the way we did this was similar to what
David Hockney did in this picture. This is an artwork by David Hockney. And it's called
Photo Montage. He took a large number of frames, each covering a small area of the scene, and
then he patched them together to make overall a wide-angle view.
And if you look carefully, you can see a few discontinuities where the sun has shifted
and the clouds have moved in the period when he was taking these pictures. But it's a good
way of making a very large panoramic view. So with these preliminaries out of the way,
I want to fire up this surround screen in this room and show you the view of our universe
in the infrared. And this is now circling 270-degree view around the room.
And so what you're seeing here primarily is our own Galaxy, the Milky Way. So there's
actually stuff that should be projected on the roof and the floor. But what we're seeing
is the Galaxy extending all the way around us. We can zoom in on this picture. This particular
picture is 19,000 pixels across. But, really, the actual data set is much bigger than that.
And so if we zoom in on a particular spot in the Milky Way, then we get here to the
Tadpole Nebula. Now, the Tadpole Nebula is a region in our Milky Way. It's about 12,000
light years away. And it's a place where hot young stars are being formed. You can see
the dust heated by them. And then if we look at a slightly different
view here, you can now notice -- now what we've done is turned off what we call artifact
rejection, which takes away things that only show up on one frame, and put everything in.
And you can see strings of green dots in the boxes. And these are actually asteroids moving
through this image as it was taken, many different frames were taken. So each image of an asteroid
is one and a half hours later, and they move. And so we can actually measure the size of
160,000 different asteroids, including 600 near-Earth objects that might be hazardous
to the Earth. We can go back out to the full sky.
All right. Now we're back. And now we can go out to 2 million light years away, to our
nearest neighbor, big spiral galaxy. And we're closing in on the Andromeda Nebula. And you
can see in the Andromeda Nebula many of these star-forming regions that form outline the
spiral arms. But, really, this is just our local neighborhood in the universe.
So because we have an all-sky view, we can see things throughout the universe, or at
least throughout the observable universe. And so if we go beyond the galaxies we can
actually resolve and see the star-forming regions in to ones that just have a lot of
radiation, we will get a different view. So now here we are back to the center of the
Milky Way. Now let's go to the full sky view. And these purple dots on this full sky view
are showing galaxies that actually are producing about 1,000 to 10,000 times more luminosity
than the Milky Way or the Andromeda Nebula. In the most distant of these, the light has
taken about 12 billion years to reach us. So we are way far out, much further away than
Andromeda. So I'd just like to close back to this wonderful
all sky view of our universe. And this is the world around us, at least on the largest
possible scales. Thank you.
[ Applause. ]