Thank you to Draper and its Hack the Moon initiative for supporting PBS Digital Studios.
These black stones are volcanic rock, and
this is one of the youngest patches of land on planet Earth, but that same
geological event that built this land has provided another window: it allows us
to observe a time when the universe was still cooling from the fire of its own formation.
And to see this, all we have to do is travel to a telescope on top of the tallest volcano in the world.
So, we're driving up to the summit of Mauna Kea on the Big Island of Hawaii.
This is the tallest volcano on the planet.
At 4,200 meters, the oxygen up here is 60% sea level, but astronomers deal with it
because it is the premier astronomical observing site in the northern hemisphere.
To Hawaiians it is a sacred site. And to astronomers,
it's where the Earth meets the universe.
Wow! It's amazing up here.
It's like being on another planet. I can already feel the
effect of the thinner atmosphere. My natural impulse, bizarrely, is to hold my
breath. Must remember to keep breathing.
Here we have 13 of the greatest telescopes in the world, operated by 11 different countries.
We have the Japanese Subaru telescope, the twin Keck domes, over here we have the
Canada/France/Hawaii telescope, and this is Gemini.
That's where we're going.
We're here to talk about a very special observation. In the spring of 2017,
astronomers turned Gemini's great mirror towards the constellation of Boötes, the plowman.
They were looking for a faint speck of light that had been noticed in
one of our great surveys of the sky. Astronomers guessed the speck was
a quasar - a vortex of radiant matter falling into a giant black hole.
Now, quasars are the most luminous objects in the universe. What was strange
about this one was its distance. Its light was SO red that astronomers
realized that that light must have been stretched out – redshifted – by traveling
many billions of years through our expanding universe. The quasar appeared
to be more distant than any we had ever seen. But that doesn't mean we can't
unravel their mysteries. And Gemini did exactly that. To find out how,
we're going to need to go inside.
You've got to see this, it's incredible.
Meet the Gemini telescope. This is what a world-class telescope looks like these days.
It is enormous. I still remember the first time I came to a telescope like this.
It blew me away. Look at the size of this thing.
This is our window to the universe.
It's cold in here.
They keep the dome at the temperature of the upcoming night so that the giant
structure doesn't warp and twist with the change in temperature.
It's a little below freezing right now. And you hear that sound?
That's the cryogenics. They keep the sensitive infrared cameras at 15 above absolute zero.
Let's actually talk about light for a second.
Light is a wave and the wavelength of that wave determines the properties of light.
For example, visible light – the wavelength range that our eyes are sensitive to –
spans only a tiny fraction of the spectrum.
That's why we create telescopes – the universe looks
very, very different at different wavelengths.
For example, viewed in visible light, the Andromeda galaxy shows us newborn stars.
Our atmosphere is transparent to visible light, so a ground-based telescope can see a
visible universe, as can we. Gemini is built to be sensitive to the infrared.
The infrared Andromeda is a swirl of star-forming clouds and gas.
Some infrared light also makes it through the atmosphere, though it helps to be up here
on a mountaintop. Although the air above the observatory is crystal clear,
it still blurs distant light somewhat. Turbulence in the atmosphere causes
incoming wavefronts of light to be warped, and it blurs our view.
To correct this, Gemini uses adaptive optics. It has a deformable mirror that flexes
and bends to match and correct the warping of incoming light. To do this in
real time, Gemini creates its own artificial guide star by shooting lasers
to twinkle off sodium atoms at 90km height, right off the edge of space.
This is the instrument used to analyze the most distant quasar.
It's the Gemini North Infrared Spectrograph – GNIRS.
A spectrograph takes incoming light and breaks it into its component wavelengths, similar to a prism,
and it records how much energy is received at each wavelength. We called that a spectrum.
When the light analyzed by this machine left its quasar, it was ultraviolet.
But traveling through the expanding universe sapped energy and
stretched the wavelength of that light so that it was infrared by the time it
reached the earth and this spectrograph. Their redshift tells us how long that
light has been traveling – 13.1 billion years, meaning the quasar lived
when the universe was only 5% its current age.
There's a broad blank patch in the quasar's spectrum – it's a stretch of nothing that tells us a ton.
Shortly after the Big Bang, when things had cooled down a bit, the universe was
filled with hydrogen gas. It was murky, especially for ultraviolet lights.
Now, that gas collapsed into the very first stars, then the very first galaxies.
Those stars eventually melted away the remaining hydrogen in a process
called reionization, leaving a crystal-clear universe.
But this quasar shines out from the era of those first stars before they'd finished the job of reionization.
Much of the quasars once ultraviolet light was sucked up before it escaped the early universe.
And what about the supermassive black hole at the center of the quasar?
The same signature wavelengths used to measure redshift are also broadened
due to the extreme speeds of matter moving near the black hole. That allows us to
estimate the mass of the black hole:
800 million Suns.
If it replaced our Sun, it would easily swallow Saturn's orbit.
Scientists struggled to figure out how it could grow to that
insane size in a tiny fraction of the age of the universe. We are expanding our
understanding of physics to figure this one out.
That tiny speck is both a revelation and a mystery. It literally shines a light on the
earliest epochs of our universe, teaching us about our most fundamental origins.
But it also opens new questions.
And our great telescopes – our portals to the universe past and present –
will tackle those questions too and ultimately bring us closer to
understanding this mysterious, this magnificent space time.
Thanks to advances in our understanding of general relativity and some mind-blowing
advances in technology, there are other ways humanity can see the universe
beyond the electromagnetic spectrum that we observe with traditional telescopes.
We can now see ripples in the fabric of space time itself.
Look out for Physics Girl's exploration of gravitational waves at LIGO.
Thank you to Draper and its Hack the Moon initiative for supporting PBS Digital Studios.
You know the story of the astronauts who landed on the Moon.
Now you can visit WeHackTheMoon.com
to discover the story of the male and female engineers who guided them there and back safely.
Hack the Moon chronicles the engineers and technologies behind the Apollo missions.
Brought to you by Draper, the site is full of images, videos, and stories about
the people who hacked the moon.
PBS is bringing you the universe with the SUMMER OF SPACE,
which includes six incredible new science and history shows
airing on PBS and streaming on pbs.org and the PBS video app.
Watch it all on PBS.org/SummerOfSpace.