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Natasha Hurley-Walker: How radio telescopes show us unseen galaxies
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Our universe is strange, wonderful and vast, says astronomer Natasha Hurley-Walker. A spaceship can't carry you into its depths (yet) -- but a radio telescope can. In this mesmerizing talk, Hurley-Walker shows how she probes the mysteries of the universe using special technology that reveals light spectrums we can't see.
Natasha Hurley-Walker - Astronomer
Natasha Hurley-Walker uses novel radio telescopes to explore the universe at some of the longest wavelengths of light. Full bio
Natasha Hurley-Walker uses novel radio telescopes to explore the universe at some of the longest wavelengths of light. Full bio
Double-click the English transcript below to play the video.
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Space, the final frontier.
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I first heard these words
when I was just six years old,
when I was just six years old,
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and I was completely inspired.
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I wanted to explore strange new worlds.
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I wanted to seek out new life.
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I wanted to see everything
that the universe had to offer.
that the universe had to offer.
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And those dreams, those words,
they took me on a journey,
they took me on a journey,
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a journey of discovery,
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through school, through university,
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to do a PhD and finally
to become a professional astronomer.
to become a professional astronomer.
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Now, I learned two amazing things,
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one slightly unfortunate,
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when I was doing my PhD.
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I learned that the reality was
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I wouldn't be piloting
a starship anytime soon.
a starship anytime soon.
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But I also learned that the universe
is strange, wonderful and vast,
is strange, wonderful and vast,
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actually too vast
to be explored by spaceship.
to be explored by spaceship.
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And so I turned my attention
to astronomy, to using telescopes.
to astronomy, to using telescopes.
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Now, I show you before you
an image of the night sky.
an image of the night sky.
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You might see it anywhere in the world.
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And all of these stars are part
of our local galaxy, the Milky Way.
of our local galaxy, the Milky Way.
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Now, if you were to go
to a darker part of the sky,
to a darker part of the sky,
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a nice dark site, perhaps in the desert,
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you might see the center
of our Milky Way galaxy
of our Milky Way galaxy
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spread out before you,
hundreds of billions of stars.
hundreds of billions of stars.
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And it's a very beautiful image.
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It's colorful.
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And again, this is just
a local corner of our universe.
a local corner of our universe.
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You can see there's
a sort of strange dark dust across it.
a sort of strange dark dust across it.
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Now, that is local dust
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that's obscuring the light of the stars.
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But we can do a pretty good job.
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Just with our own eyes, we can explore
our little corner of the universe.
our little corner of the universe.
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It's possible to do better.
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You can use wonderful telescopes
like the Hubble Space Telescope.
like the Hubble Space Telescope.
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Now, astronomers
have put together this image.
have put together this image.
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It's called the Hubble Deep Field,
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and they've spent hundreds of hours
observing just a tiny patch of the sky
observing just a tiny patch of the sky
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no larger than your thumbnail
held at arm's length.
held at arm's length.
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And in this image
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you can see thousands of galaxies,
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and we know that there must be
hundreds of millions, billions of galaxies
hundreds of millions, billions of galaxies
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in the entire universe,
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some like our own and some very different.
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So you think, OK, well,
I can continue this journey.
I can continue this journey.
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This is easy. I can just
use a very powerful telescope
use a very powerful telescope
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and just look at the sky, no problem.
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It's actually really missing out
if we just do that.
if we just do that.
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Now, that's because
everything I've talked about so far
everything I've talked about so far
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is just using the visible spectrum,
just the thing that your eyes can see,
just the thing that your eyes can see,
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and that's a tiny slice,
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a tiny, tiny slice
of what the universe has to offer us.
of what the universe has to offer us.
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Now, there's also two very important
problems with using visible light.
problems with using visible light.
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Not only are we missing out
on all the other processes
on all the other processes
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that are emitting other kinds of light,
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but there's two issues.
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Now, the first is that dust
that I mentioned earlier.
that I mentioned earlier.
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The dust stops the visible light
from getting to us.
from getting to us.
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So as we look deeper
into the universe, we see less light.
into the universe, we see less light.
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The dust stops it getting to us.
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But there's a really strange problem
with using visible light
with using visible light
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in order to try and explore the universe.
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Now take a break for a minute.
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Say you're standing on a corner,
a busy street corner.
a busy street corner.
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There's cars going by.
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An ambulance approaches.
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It has a high-pitched siren.
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(Imitates a siren passing by)
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The siren appeared to change in pitch
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as it moved towards and away from you.
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The ambulance driver did not change
the siren just to mess with you.
the siren just to mess with you.
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That was a product of your perception.
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The sound waves,
as the ambulance approached,
as the ambulance approached,
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were compressed,
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and they changed higher in pitch.
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As the ambulance receded,
the sound waves were stretched,
the sound waves were stretched,
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and they sounded lower in pitch.
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The same thing happens with light.
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Objects moving towards us,
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their light waves are compressed
and they appear bluer.
and they appear bluer.
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Objects moving away from us,
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their light waves are stretched,
and they appear redder.
and they appear redder.
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So we call these effects
blueshift and redshift.
blueshift and redshift.
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Now, our universe is expanding,
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so everything is moving away
from everything else,
from everything else,
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and that means
everything appears to be red.
everything appears to be red.
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And oddly enough, as you look
more deeply into the universe,
more deeply into the universe,
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more distant objects
are moving away further and faster,
are moving away further and faster,
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so they appear more red.
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So if I come back to the Hubble Deep Field
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and we were to continue
to peer deeply into the universe
to peer deeply into the universe
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just using the Hubble,
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as we get to a certain distance away,
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everything becomes red,
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and that presents something of a problem.
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Eventually, we get so far away
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everything is shifted into the infrared
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and we can't see anything at all.
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So there must be a way around this.
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Otherwise, I'm limited in my journey.
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I wanted to explore the whole universe,
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not just whatever I can see,
you know, before the redshift kicks in.
you know, before the redshift kicks in.
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There is a technique.
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It's called radio astronomy.
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Astronomers have been
using this for decades.
using this for decades.
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It's a fantastic technique.
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I show you the Parkes Radio Telescope,
affectionately known as "The Dish."
affectionately known as "The Dish."
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You may have seen the movie.
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And radio is really brilliant.
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It allows us to peer much more deeply.
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It doesn't get stopped by dust,
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so you can see everything in the universe,
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and redshift is less of a problem
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because we can build receivers
that receive across a large band.
that receive across a large band.
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So what does Parkes see when we turn it
to the center of the Milky Way?
to the center of the Milky Way?
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We should see something fantastic, right?
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Well, we do see something interesting.
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All that dust has gone.
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As I mentioned, radio goes
straight through dust, so not a problem.
straight through dust, so not a problem.
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But the view is very different.
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We can see that the center
of the Milky Way is aglow,
of the Milky Way is aglow,
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and this isn't starlight.
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This is a light called
synchrotron radiation,
synchrotron radiation,
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and it's formed from electrons
spiraling around cosmic magnetic fields.
spiraling around cosmic magnetic fields.
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So the plane is aglow with this light.
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And we can also see
strange tufts coming off of it,
strange tufts coming off of it,
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and objects which don't appear to line up
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with anything that we can see
with our own eyes.
with our own eyes.
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But it's hard to really
interpret this image,
interpret this image,
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because as you can see,
it's very low resolution.
it's very low resolution.
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Radio waves have a wavelength that's long,
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and that makes their resolution poorer.
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This image is also black and white,
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so we don't really know
what is the color of everything in here.
what is the color of everything in here.
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Well, fast-forward to today.
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We can build telescopes
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which can get over these problems.
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Now, I'm showing you here an image
of the Murchison Radio Observatory,
of the Murchison Radio Observatory,
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a fantastic place
to build radio telescopes.
to build radio telescopes.
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It's flat, it's dry,
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and most importantly, it's radio quiet:
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no mobile phones, no Wi-Fi, nothing,
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just very, very radio quiet,
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so a perfect place
to build a radio telescope.
to build a radio telescope.
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Now, the telescope that I've been
working on for a few years
working on for a few years
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is called the Murchison Widefield Array,
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and I'm going to show you
a little time lapse of it being built.
a little time lapse of it being built.
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This is a group of undergraduate
and postgraduate students
and postgraduate students
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located in Perth.
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We call them the Student Army,
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and they volunteered their time
to build a radio telescope.
to build a radio telescope.
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There's no course credit for this.
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And they're putting together
these radio dipoles.
these radio dipoles.
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They just receive at low frequencies,
a bit like your FM radio or your TV.
a bit like your FM radio or your TV.
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And here we are deploying them
across the desert.
across the desert.
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The final telescope
covers 10 square kilometers
covers 10 square kilometers
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of the Western Australian desert.
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And the interesting thing is,
there's no moving parts.
there's no moving parts.
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We just deploy these little antennas
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essentially on chicken mesh.
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It's fairly cheap.
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Cables take the signals
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from the antennas
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and bring them
to central processing units.
to central processing units.
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And it's the size of this telescope,
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the fact that we've built it
over the entire desert
over the entire desert
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that gives us a better
resolution than Parkes.
resolution than Parkes.
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Now, eventually all those cables
bring them to a unit
bring them to a unit
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which sends it off
to a supercomputer here in Perth,
to a supercomputer here in Perth,
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and that's where I come in.
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(Sighs)
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Radio data.
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I have spent the last five years
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working with very difficult,
very interesting data
very interesting data
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that no one had really looked at before.
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I've spent a long time calibrating it,
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running millions of CPU hours
on supercomputers
on supercomputers
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and really trying to understand that data.
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And with this telescope,
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with this data,
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we've performed a survey
of the entire southern sky,
of the entire southern sky,
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the GaLactic and Extragalactic
All-sky MWA Survey,
All-sky MWA Survey,
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or GLEAM, as I call it.
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And I'm very excited.
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This survey is just about to be published,
but it hasn't been shown yet,
but it hasn't been shown yet,
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so you are literally the first people
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to see this southern survey
of the entire sky.
of the entire sky.
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So I'm delighted to share with you
some images from this survey.
some images from this survey.
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Now, imagine you went to the Murchison,
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you camped out underneath the stars
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and you looked towards the south.
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You saw the south's celestial pole,
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the galaxy rising.
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If I fade in the radio light,
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this is what we observe with our survey.
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You can see that the galactic plane
is no longer dark with dust.
is no longer dark with dust.
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It's alight with synchrotron radiation,
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and thousands of dots are in the sky.
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Our large Magellanic Cloud,
our nearest galactic neighbor,
our nearest galactic neighbor,
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is orange instead
of its more familiar blue-white.
of its more familiar blue-white.
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So there's a lot going on in this.
Let's take a closer look.
Let's take a closer look.
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If we look back
towards the galactic center,
towards the galactic center,
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where we originally saw the Parkes image
that I showed you earlier,
that I showed you earlier,
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low resolution, black and white,
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and we fade to the GLEAM view,
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you can see the resolution
has gone up by a factor of a hundred.
has gone up by a factor of a hundred.
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We now have a color view of the sky,
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a technicolor view.
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Now, it's not a false color view.
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These are real radio colors.
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What I've done is I've colored
the lowest frequencies red
the lowest frequencies red
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and the highest frequencies blue,
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and the middle ones green.
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And that gives us this rainbow view.
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And this isn't just false color.
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The colors in this image
tell us about the physical processes
tell us about the physical processes
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going on in the universe.
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So for instance, if you look
along the plane of the galaxy,
along the plane of the galaxy,
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it's alight with synchrotron,
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which is mostly reddish orange,
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but if we look very closely,
we see little blue dots.
we see little blue dots.
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Now, if we zoom in,
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these blue dots are ionized plasma
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around very bright stars,
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and what happens
is that they block the red light,
is that they block the red light,
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so they appear blue.
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And these can tell us
about these star-forming regions
about these star-forming regions
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in our galaxy.
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And we just see them immediately.
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We look at the galaxy,
and the color tells us that they're there.
and the color tells us that they're there.
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You can see little soap bubbles,
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little circular images
around the galactic plane,
around the galactic plane,
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and these are supernova remnants.
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When a star explodes,
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its outer shell is cast off
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and it travels outward into space
gathering up material,
gathering up material,
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and it produces a little shell.
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It's been a long-standing
mystery to astronomers
mystery to astronomers
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where all the supernova remnants are.
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We know that there must be a lot
of high-energy electrons in the plane
of high-energy electrons in the plane
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to produce the synchrotron
radiation that we see,
radiation that we see,
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and we think they're produced
by supernova remnants,
by supernova remnants,
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but there don't seem to be enough.
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Fortunately, GLEAM is really, really
good at detecting supernova remnants,
good at detecting supernova remnants,
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so we're hoping to have
a new paper out on that soon.
a new paper out on that soon.
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Now, that's fine.
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We've explored our little local universe,
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but I wanted to go deeper,
I wanted to go further.
I wanted to go further.
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I wanted to go beyond the Milky Way.
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Well, as it happens, we can see a very
interesting object in the top right,
interesting object in the top right,
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and this is a local radio galaxy,
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Centaurus A.
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If we zoom in on this,
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we can see that there are
two huge plumes going out into space.
two huge plumes going out into space.
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And if you look right in the center
between those two plumes,
between those two plumes,
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you'll see a galaxy just like our own.
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It's a spiral. It has a dust lane.
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It's a normal galaxy.
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But these jets
are only visible in the radio.
are only visible in the radio.
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If we looked in the visible,
we wouldn't even know they were there,
we wouldn't even know they were there,
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and they're thousands of times larger
than the host galaxy.
than the host galaxy.
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What's going on?
What's producing these jets?
What's producing these jets?
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At the center of every galaxy
that we know about
that we know about
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is a supermassive black hole.
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Now, black holes are invisible.
That's why they're called that.
That's why they're called that.
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All you can see is the deflection
of the light around them,
of the light around them,
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and occasionally, when a star
or a cloud of gas comes into their orbit,
or a cloud of gas comes into their orbit,
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it is ripped apart by tidal forces,
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forming what we call an accretion disk.
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The accretion disk
glows brightly in the x-rays,
glows brightly in the x-rays,
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and huge magnetic fields
can launch the material into space
can launch the material into space
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at nearly the speed of light.
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So these jets are visible in the radio
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and this is what we pick up in our survey.
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Well, very well, so we've seen
one radio galaxy. That's nice.
one radio galaxy. That's nice.
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But if you just look
at the top of that image,
at the top of that image,
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you'll see another radio galaxy.
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It's a little bit smaller,
and that's just because it's further away.
and that's just because it's further away.
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OK. Two radio galaxies.
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We can see this. This is fine.
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Well, what about all the other dots?
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Presumably those are just stars.
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They're not.
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They're all radio galaxies.
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Every single one of the dots in this image
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is a distant galaxy,
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millions to billions of light-years away
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with a supermassive
black hole at its center
black hole at its center
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pushing material into space
at nearly the speed of light.
at nearly the speed of light.
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It is mind-blowing.
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And this survey is even larger
than what I've shown here.
than what I've shown here.
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If we zoom out to
the full extent of the survey,
the full extent of the survey,
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you can see I found 300,000
of these radio galaxies.
of these radio galaxies.
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So it's truly an epic journey.
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We've discovered all of these galaxies
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right back to the very first
supermassive black holes.
supermassive black holes.
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I'm very proud of this,
and it will be published next week.
and it will be published next week.
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Now, that's not all.
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I've explored the furthest reaches
of the galaxy with this survey,
of the galaxy with this survey,
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but there's something
even more in this image.
even more in this image.
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Now, I'll take you right back
to the dawn of time.
to the dawn of time.
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When the universe formed,
it was a big bang,
it was a big bang,
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which left the universe
as a sea of hydrogen,
as a sea of hydrogen,
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neutral hydrogen.
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And when the very first stars
and galaxies switched on,
and galaxies switched on,
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they ionized that hydrogen.
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So the universe went
from neutral to ionized.
from neutral to ionized.
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That imprinted a signal all around us.
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Everywhere, it pervades us,
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like the Force.
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Now, because that happened so long ago,
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the signal was redshifted,
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so now that signal
is at very low frequencies.
is at very low frequencies.
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It's at the same frequency as my survey,
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but it's so faint.
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It's a billionth the size
of any of the objects in my survey.
of any of the objects in my survey.
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So our telescope may not be quite
sensitive enough to pick up this signal.
sensitive enough to pick up this signal.
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However, there's a new radio telescope.
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So I can't have a starship,
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but I can hopefully have
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one of the biggest
radio telescopes in the world.
radio telescopes in the world.
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We're building the Square Kilometre Array,
a new radio telescope,
a new radio telescope,
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and it's going to be a thousand
times bigger than the MWA,
times bigger than the MWA,
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a thousand times more sensitive,
and have an even better resolution.
and have an even better resolution.
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So we should find
tens of millions of galaxies.
tens of millions of galaxies.
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And perhaps, deep in that signal,
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I will get to look upon the very first
stars and galaxies switching on,
stars and galaxies switching on,
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the beginning of time itself.
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Thank you.
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(Applause)
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ABOUT THE SPEAKER
Natasha Hurley-Walker - AstronomerNatasha Hurley-Walker uses novel radio telescopes to explore the universe at some of the longest wavelengths of light.
Why you should listen
Dr. Natasha Hurley-Walker recently completed an astronomical survey of the entire southern sky, revealing the radio glow of our own Milky Way galaxy as well as hundreds of thousands of distant galaxies: the GaLactic and Extragalactic All-sky Murchison Widefield Array (GLEAM) survey. Unlike previous work, GLEAM is the first "radio color" survey, observed across such a wide range of frequencies that the unique spectrum of every object can be used to understand its underlying physics.
An Early-Career Research Fellow based at the Curtin University node of the International Centre for Radio Astronomy Research, in Perth, Western Australia, Hurley-Walker is part of the international Murchison Widefield Array (MWA) collaboration, spanning thirteen institutes across six countries. At her fingertips are tens of petabytes of data collected by the MWA since 2013, which she processes using powerful supercomputers at the nearby Pawsey Centre. Hurley-Walker earned a PhD in Radio Astronomy at the University of Cambridge by commissioning and using a new radio telescope to perform its first science observations. The experience directly transferred to the MWA, which she also helped to commission.
The MWA is a precursor to the Square Kilometer Array (SKA), what will be the largest radio telescope in the world, set to come online in the 2020s. By developing software and techniques to deal with data from the MWA, creating pathfinding maps of the sky and training a new generation of astronomers in cutting-edge techniques, Hurley-Walker is working to lay the scientific groundwork for the commissioning of the SKA. In 2016 Hurley-Walker was awarded an Australian SKA Fellowship in order to visit the SKA headquarters and transfer lessons from her commissioning experiences as well as develop her survey into a useful calibration model for the SKA.
Hurley-Walker is passionate about scientific outreach and keynoted talks in 2013 and 2017 at Astrofest, Australia's largest public astronomy festival. So that anyone in the world can see the sky with the same radio eyes as her, she created the GLEAMoscope , an interactive online viewer that shows the universe at radio wavelengths compared to other frequencies, including the more familiar "optical" spectrum. It being the 21st century, there's also an app: check out GLEAM on the Google Play store. In 2017 Natasha won the "Best Timelapse" category in the Astofest astrophotography competition with her colleague John Goldsmith for their creation of a composite video showing both the optical and radio sky. For more detail on Hurley-Walker's work, check out her article on TheConversation.
Working with cutting-edge data is tough, but sometimes hides serendipitous gems which Hurley-Walker has unearthed, like the faintest dying radio galaxy ever discovered, whistling plasma ducts in the Earth's ionosphere and some of the youngest and weirdest radio galaxies ever found. View a complete list of Hurley-Walker's publications.
Natasha Hurley-Walker | Speaker | TED.com