[♩INTRO]
The Hubble Space Telescope literally changed the way we see the universe.
Since it launched in 1990, thirty years ago this year,
it’s snapped more than a million images,
from close-ups of nearby planets to the farthest galaxy ever detected.
Chances are, most of the iconic space pictures you’ve seen
have come from Hubble.
But those images aren’t just stunning and beautiful;
they’ve also shaped the way we imagine and study space.
They’ve let us measure the universe’s age,
have shown us that the universe’s expansion is accelerating,
and have given us a look at planets around other stars.
Here’s why this telescope is so good at creating them.
First, Hubble has a leg up by being in space.
Since it doesn’t have to deal with turbulent air molecules, which blur light,
it can pick out details more than ten times sharper
than the best telescopes on the ground.
On top of that, it can detect wavelengths
that Earth’s atmosphere blocks out altogether, like UV rays.
That lets us see lots of things, like newly forming stars
and matter spiraling into black holes, that we can’t see the same way from Earth.
In fact, Hubble can pick up wavelengths both longer and shorter than visible light!
Turning all of those wavelengths into a pretty picture, though,
is a whole other story, because no matter what Hubble can see,
our eyes can still only see things in the visible spectrum.
And it takes some processing to turn raw Hubble data into a color photo.
As a first step, Hubble actually gathers all its raw data in black-and-white.
It has filters that only let through light at specific wavelengths,
and when photons, or particles of light, pass through,
an electronic detector records where they land.
So you end up with a pattern of photons from a single wavelength,
which translates into a black-and-white image.
But since different astronomical phenomena emit different kinds of light,
a single wavelength usually won’t give you a complete picture.
For instance, if you look at the nearby Triangulum Galaxy at X-ray wavelengths,
you’ll see mostly interstellar gas.
At UV wavelengths, you’ll see regions of star formation.
The visible spectrum will show you the stars.
And radio waves will give you a map of hydrogen gas.
In other words, each wavelength tells a totally different story!
So Hubble records a bunch of black-and-white images at different wavelengths.
Then it’s time to put them together and add color.
Astronomers assign colors to each of the wavelengths of light.
If all the wavelengths fall in the visible spectrum,
they can assign each wavelength its true color.
But often, they’re dealing with wavelengths we wouldn’t ordinarily be able to see.
In those cases, astronomers assign those invisible wavelengths
a color from the visual spectrum.
They might color all X-rays shades of blue, for example.
The colors they choose can help them highlight features
or subtle details in the targets they’re exploring.
And it might not be exactly what you’d see if your eyes were
as powerful as Hubble, but as surreal as it looks, it’s all based on real data.
Finally, part of the reason these images are so stunning in the first place
is because Hubble collects incredible data.
Many of Hubble’s sources are really faint,
so it takes a long time to collect enough light to produce a meaningful picture.
And in a way, there’s nothing novel about how Hubble does that:
It collects light a lot like a camera does during a long exposure
except... it’s also hurtling around the Earth at about 8 kilometers a second,
trying to stay focused on a single speck the whole time.
Since it’s not just sitting still like a camera normally would be,
it needs to be able to point really precisely over and over and over again,
often hundreds of times, as it zooms through its orbit.
To do that, it has special tools called fine guidance sensors.
Two of these super-sensitive detectors lock onto bright stars, or guide stars,
on either side of the target Hubble’s aiming to photograph.
Then, forty times a second, they lock back onto the guide stars
to make sure Hubble’s position stays sharp.
For most observations, Hubble also has to deal with the fact that Earth
gets in the way of what it’s trying to see.
Every 45 minutes or so, as Hubble orbits the Earth, our planet eclipses its target.
When that happens, the cameras shut down
until the telescope comes out the other side.
At that point, the fine guidance sensors have to quickly snap back
onto the original guide stars and bring the target back into focus.
And these sensors are so good at what they do that Hubble is extremely stable,
and it can focus on really faint, distant objects with hardly any blur.
Like, if your eyes were as good as Hubble, and you stood in Washington, D.C.
looking at Tokyo, you’d be able to make out two fireflies just 3 meters apart.
So, Hubble has some really impressive tricks for creating the pictures
it’s so famous for.
And it helped usher in a whole generation of space telescopes
that use similar tools to study the universe in different ways.
But even as it ages, Hubble has remained iconic.
Its images have reached way past NASA into the everyday world,
where they’ve been inspiring people for decades.
And they’ve also had an important scientific role.
They’ve helped us understand the complex stories each wavelength tells
about an astronomical object, and how those stories are intertwined.
For instance, the iconic image called Pillars of Creation
is a nebula full of stars being born.
But the optical and UV starlight we’d normally see gets absorbed
by dust and re-emitted in infrared.
Hubble picked up that infrared light, and by creating an image
that combined different wavelengths, astronomers could actually see
how many stars were inside the nebula
and how they were interacting with clouds inside the pillars.
They were able to do a similar thing with the star Eta Carinae,
which shines at us from the Great Carina Nebula,
one of the largest star-forming regions in our galaxy.
Colored photos bring out the features of this star and its environment
and let us see the dust, gas, and newly forming stars.
Our Sun and solar system may have come out of a system a lot like this,
so having the chance to explore this star and its nebula this way
gives us a fascinating window into our own possible origins.
And if nothing else, it shows us what star formation is like
in the dense spiral arms of our galaxy.
Whether they’re informing complex ideas about where we came from
or making images of galaxies mainstream,
Hubble’s photos have shaped the way a lot of us imagine space.
They’ve given us three decades’ worth of science,
and they still have a lot to offer our research and imagination.
This episode wouldn’t have been possible without the team
at NASA’s Goddard Space Flight Center,
who provided a lot of the information we used.
And we’d like to give a special thanks to Jim Jeletic, Ken Carpenter,
Joe Depasquale, Mike Wenz, Erin Kisliuk, and Courtney Lee.
We’d also like to thank our patrons on Patreon, who make it possible for us
to share amazing science like this.
It takes a lot of people to make a SciShow video,
and we couldn’t do it without your support.
If you’re not a patron but would like to help us keep SciShow going,
you can learn more at patreon.com/SciShow.
And, as always, thanks for watching SciShow Space.
[♩OUTRO]