A stellar history of modern astronomy

Astronomers once gazed upon the night sky and counted every star in the galaxy by hand. The process has evolved since then, but the thirst for celestial knowledge remains the same. Join astrophysicist Emily Levesque for an anecdote-rich jaunt through the technological history of photographing the cosmos and learn about the one constant that makes it all work: human curiosity.

In 1987, a Chilean engineer
named Oscar Duhalde

became the only
living person on the planet

to discover a rare astronomical event

with the naked eye.

Oscar was a telescope operator
at Las Campanas Observatory in Chile.

He worked with the astronomers who came
to the observatory for their research,

running the telescopes and processing
the data that they took.

On the night of February 24th,

Oscar stepped outside for a break

and looked up at the night sky
and he saw this.

This is the Large Magellanic Cloud.

It's a satellite galaxy very near
our own Milky Way.

But on that February night,

Oscar noticed that something
was different about this galaxy.

It didn't quite look like this.

It looked like this.

Did you see it?

(Laughter)

A small point of light had appeared
in one corner of this galaxy.

So to explain how amazing it is
that Oscar noticed this,

we need to zoom out a bit

and look at what the southern
sky in Chile looks like.

The Large Magellanic Cloud
is right in the middle of that image,

but despite its name, it's really small.

Imagine trying to notice
one single new point of light

appearing in that galaxy.

Oscar was able to do this

because he had the Large Magellanic Cloud
essentially memorized.

He had worked on data
from this galaxy for years,

poring over night after night
of observations

and doing it by hand,

because Oscar had begun
his work in astronomy

at a time when we stored all of the data
that we observed from the universe

on fragile sheets of glass.

I know that today's theme is "Moonshot,"

and as an astronomer, I figured
I could start us out nice and literally,

so here's a shot of the Moon.

(Laughter)

It's a familiar sight to all of us,
but there's a couple of unusual things

about this particular image.

For one, I flipped the colors.

It originally looked like this.

And if we zoom out, we can see
how this picture was taken.

This is a photograph
of the Moon taken in 1894

on a glass photographic plate.

This was the technology that astronomers
had available for decades

to store the observations
that we took of the night sky.

I've actually brought an example
of a glass plate to show you.

So this looks like a real secure way
to store our data.

These photographic plates
were incredibly difficult to work with.

One side of them was treated
with a chemical emulsion that would darken

when it was exposed to light.

This is how these plates were able
to store the pictures that they took,

but it meant that astronomers
had to work with these plates in darkness.

The plates had to be cut
to a specific size

so that they could fit
into the camera of a telescope.

So astronomers would take
razor-sharp cutting tools

and slice these tiny pieces of glass,

all in the dark.

Astronomers also had all kinds of tricks
that they would use

to make the plates
respond to light a little faster.

They would bake them or freeze them,
they would soak them in ammonia,

or they'd coat them with lemon juice --

all in the dark.

Then astronomers would take
these carefully designed plates

to the telescope

and load them into the camera.

They had to be loaded with that
chemically emulsified side pointed out

so that the light would hit it.

But in the dark, it was almost impossible
to tell which side was the right one.

Astronomers got into the habit
of tapping a plate to their lips,

or, like, licking it, to see
which side of the plate was sticky

and therefore coated with the emulsion.

And then when they actually
put it into the camera,

there was one last challenge.

In this picture behind me,

you can see that the plate
the astronomer is holding

is very slightly curved.

Sometimes plates had to be bent
to fit into a telescope's camera,

so you would take this carefully cut,
meticulously treated, very babied plate

up to a telescope, and then you'd just ...

So sometimes that would work.
Sometimes they would snap.

But it would usually end
with the [plate] loaded into a camera

on the back of a telescope.

You could then point that telescope

to whatever patch of sky
you wanted to study,

open the camera shutter,

and begin capturing data.

Now, astronomers couldn't just
walk away from the camera

once they'd done this.

They had to stay with that camera
for as long as they were observing.

This meant that astronomers
would get into elevators

attached to the side
of the telescope domes.

They would ride the elevator
high into the building

and then climb into
the top of the telescope

and stay there all night
shivering in the cold,

transferring plates
in and out of the camera,

opening and closing the shutter

and pointing the telescope
to whatever piece of sky

they wanted to study.

These astronomers worked with operators
who would stay on the ground.

And they would do things
like turn the dome itself

and make sure the rest
of the telescope was running.

It was a system that usually
worked pretty well,

but once in a while,
things would go wrong.

There was an astronomer observing
a very complicated plate

at this observatory,
the Lick Observatory here in California.

He was sitting at the top
of that yellow structure

that you see in the dome
on the lower right,

and he'd been exposing
one glass plate to the sky for hours,

crouched down and cold

and keeping the telescope
perfectly pointed

so he could take this precious
picture of the universe.

His operator wandered
into the dome at one point

just to check on him
and see how things were going.

And as the operator stepped through
the door of the dome,

he brushed against the wall
and flipped the light switch in the dome.

So the lights came blazing on
and flooding into the telescope

and ruining the plate,

and there was then this howl
from the top of the telescope.

The astronomer started yelling
and cursing and saying,

"What have you done?
You've destroyed so much hard work.

I'm going to get down
from this telescope and kill you!"

So he then starts moving the telescope

about this fast --

(Laughter)

toward the elevator

so that he can climb down
and make good on his threats.

Now, as he's approaching the elevator,

the elevator then suddenly
starts spinning away from him,

because remember, the astronomer
can control the telescope,

but the operator can control the dome.

(Laughter)

And the operator is looking up, going,

"He seems really mad. I might not want
to let him down until he's less murdery."

So the end is this absurd
slow-motion game of chase

with the lights on and the dome
just spinning around and around.

It must have looked completely ridiculous.

When I tell people about using
photographic plates to study the universe,

it does sound ridiculous.

It's a little absurd

to take what seems like a primitive tool
for studying the universe

and say, well, we're going
to dunk this in lemon juice, lick it,

stick it in the telescope,
shiver next to it for a few hours

and solve the mysteries of the cosmos.

In reality, though,
that's exactly what we did.

I showed you this picture before

of an astronomer perched
at the top of a telescope.

What I didn't tell you
is who this astronomer is.

This is Edwin Hubble,

and Hubble used photographic plates

to completely change
our entire understanding

of how big the universe is
and how it works.

This is a plate
that Hubble took back in 1923

of an object known at the time
as the Andromeda Nebula.

You can see in the upper
right of that image

that Hubble has labeled a star
with this bright red word, "Var!"

He's even put an exclamation
point next to it.

"Var" here stands for "variable."

Hubble had found a variable star
in the Andromeda Nebula.

Its brightness changed,

getting brighter and dimmer
as a function of time.

Hubble knew that if he studied
how that star changed with time,

he could measure the distance
to the Andromeda Nebula,

and when he did,
the results were astonishing.

He discovered that this was not,
in fact, a nebula.

This was the Andromeda Galaxy,

an entire separate galaxy
two and a half million light years

beyond our own Milky Way.

This was the first evidence
of other galaxies

existing in the universe beyond our own,

and it totally changed our understanding
of how big the universe was

and what it contained.

So now we can look at
what telescopes can do today.

This is a modern-day picture
of the Andromeda Galaxy,

and it looks just like
the telescope photos

that we all love to enjoy and look at:

it's colorful and detailed and beautiful.

We now store data like this digitally,

and we take it using
telescopes like these.

So this is me standing underneath
a telescope with a mirror

that's 26 feet across.

Bigger telescope mirrors let us take
sharper and clearer images,

and they also make it
easier for us to gather light

from faint and faraway objects.

So a bigger telescope literally
gives us a farther reach

into the universe,

looking at things that we
couldn't have seen before.

We're also no longer strapped
to the telescope

when we do our observations.

This is me during
my very first observing trip

at a telescope in Arizona.

I'm opening the dome of the telescope,

but I'm not on top
of the telescope to do it.

I'm sitting in a room
off to the side of the dome,

nice and warm and on the ground

and running the telescope from afar.

"Afar" can get pretty extreme.

Sometimes we don't even need
to go to telescopes anymore.

This is a telescope in New Mexico
that I use for my research all the time,

but I can run it with my laptop.

I can sit on my couch in Seattle

and send commands from my laptop

telling the telescope where to point,

when to open and close the shutter,

what pictures I want it
to take of the universe --

all from many states away.

So the way that we operate
telescopes has really changed,

but the questions we're trying to answer
about the universe

have remained the same.

One of the big questions still focuses
on how things change in the night sky,

and the changing sky was exactly
what Oscar Duhalde saw

when he looked up
with the naked eye in 1987.

This point of light that he saw appearing
in the Large Magellanic Cloud

turned out to be a supernova.

This was the first naked-eye supernova

seen from Earth in more than 400 years.

This is pretty cool,

but a couple of you might
be looking at this image and going,

"Really? I've heard of supernovae.

They're supposed to be spectacular,

and this is just like a dot
that appeared in the sky."

It's true that when you hear
the description of what a supernova is

it sounds really epic.

They're these brilliant, explosive deaths
of enormous, massive stars,

and they shoot energy
out into the universe,

and they spew material out into space,

and they sound, like, noticeable.

They sound really obvious.

The whole trick about
what a supernova looks like

has to do with where it is.

If a star were to die as a supernova

right in our backyard in the Milky Way,
a few hundred light years away --

"backyard" in astronomy terms --

it would be incredibly bright.

We would be able to see
that supernova at night

as bright as the Moon.

We would be able to read by its light.

Everybody would wind up taking photos
of this supernova on their phone.

It would be on headlines
all over the world.

It would for sure get a hashtag.

It would be impossible to miss
that a supernova had happened so nearby.

But the supernova that Oscar observed

didn't happen a few hundred
light years away.

This supernova happened
170,000 light years away,

which is why instead of an epic explosion,

it appears as a little dot.

This was still unbelievably exciting.

It was still visible with the naked eye,

and the most spectacular supernova

that we've seen since
the invention of the telescope.

But it gives you a better sense
of what most supernovae look like.

We still discover and study
supernovae all the time today,

but we do it in distant galaxies
using powerful telescopes.

We photograph the galaxy multiple times,

and we look for something that's changed.

We look for that little
pinprick of light appearing

that tells us that a star has died.

We can learn a great deal
about the universe and about stars

from supernovae,

but we don't want to leave
studying them up to chance.

We don't want to count on
happening to look up at the right time

or pointing our telescope
at the right galaxy.

What we ideally want is a telescope

that can systematically
and computationally

do what Oscar did with his mind.

Oscar was able to discover this supernova

because he had that galaxy memorized.

With digital data,

we can effectively memorize
every piece of the sky that we look at,

compare old and new observations

and look for anything that's changed.

This is the Vera Rubin Observatory

in Chile.

Now, when I visited it back in March,
it was still under construction.

But this telescope
will begin observations next year,

and when it does,

it will carry out a simple
but spectacular observing program.

This telescope will photograph
the entire southern sky

every few days

over and over,

following a preset pattern

for 10 years.

Computers and algorithms
affiliated with the observatory

will then compare every pair of images
taken of the same patch of sky,

looking for anything
that's gotten brighter or dimmer,

like a variable star,

or looking for anything that's appeared,

like a supernova.

Right now, we discover about
a thousand supernovae every year.

The Rubin Observatory will be capable
of discovering a thousand supernovae

every night.

It's going to dramatically change
the face of astronomy

and of how we study things
that change in the sky,

and it will do all of this

largely without much
human intervention at all.

It will follow that preset pattern

and computationally find
anything that's changed or appeared.

This might sound a little sad at first,

this idea that we're removing
people from stargazing.

But in reality,

our role as astronomers
isn't disappearing,

it's just moving.

We've already seen
how we do our jobs change.

We've gone from perching atop telescopes

to sitting next to them

to not even needing to go to them
or send them commands at all.

Where astronomers still shine

is in asking questions
and working with the data.

Gathering data is only the first step.

Analyzing it is where we can really apply
what we know about the universe.

Human curiosity is what makes us
ask questions like:

How big is the universe?
How did it begin?

How's it going to end? And are we alone?

So this is the power that humans
are still able to bring to astronomy.

So compare the capabilities
of a telescope like this

with the observations
that we were able to take like this.

We discovered amazing things
with glass plates,

but discovery looks different today.

The way we do astronomy
looks different today.

What hasn't changed
is that seed of human curiosity.

If we can harness the power
of tomorrow's technology

and combine it with this drive
that we all have to look up

and to ask questions
about what we see there,

we'll be ready to learn
some incredible new things

about the universe.

Thank you.

(Applause)