A stellar history of modern astronomy | Emily Levesque

Transcriber: Joseph Geni Reviewer: Camille Martínez

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)