We’re in the middle of a billion dollar telescope building boom.
The Giant Magellan Telescope.
Thirty Meter Telescope and Europe’s Extremely Large Telescope are all part of a new class
of ground based observatories that will peer farther through space and further back in
time.
“Astronomers are not very good with names.
First we built big telescopes, and then we made the very large telescope, and now we're
making extremely large telescopes.
But really what it means, it's about 10 times larger than any telescope we have today.”
They’re all racing to see first light in the 2020s.
But why now?
How did we get here?
“Typically, the size of the largest telescope on the earth doubles about every 40 years…
Around 2000 there were groups around the globe who had just finished building telescopes
of about 8 and 10 meters in diameter, and they recognized the technology could be used
to make telescopes even larger.
And that was about the time... we discovered that as astronomers we have no idea what's
actually going on in the universe.
I mean no idea in the sense that we figured out that 97% of the stuff in the universe
can't be seen and we don't know what it is.
So that was a good motivation to build bigger telescopes.”
“The technology got better for us to make this quantum jump from, you know, eight meter
to 30 meter glass...This comes down to few key elements.”
The first is a revolution in mirror size and design.
“The telescope performance are mostly driven by the size of the primary mirror.
The bigger the primary mirror, the more light we can collect….That means we can go faint
into the universe, you can look at smaller objects, more distant objects.”
The problem is you can't make one single mirror any large than about 20 feet in diameter.
There's just basic material properties in the glass that make it very difficult.
So...we have to make mirror segments.
We take the parent optical surface and kind of like with the biscuit cutter we cut it
into seven circles.
We make them to one combined parent optical surface that brings the light then to a single
focus.
We have to then hold those mirrors in place on a large steel structure that's stiff enough
that it doesn't shake in the wind, and it doesn't sag under its own weight, and then
it has to be precise enough to steer across the sky so that when we move to track the
stars or the planets there's no vibration.
And we do that strangely enough by floating the entire telescope, entire 1,000 tons on
a thin film of oil.
The telescope simply floats on that in a way that's completely frictionless.”
That’s the design for the Giant Magellan Telescope, whereas the E-ELT will take a slightly
different approach.
“The original idea was to build, not a forty meter diameter, but 100 meter diameter.
And that was called the Overwhelmingly Large Telescope, that was so big.
The engineers said "You know, this is really too much for us.
The shape of the telescope has to be precise to few tenths of nanometers.
So, the width of a hair across the entire forty meter diameter of the primary, which
is, actually, not even one single piece.
It's made of 798 individual smaller mirrors.
Each of them needs to be polished, extremely accurate, and then controlled extremely accurate,
to mimic this uniform surface at the nanometer level.”
These enormous precision machines will be built in some of the driest and most remote
places on earth, complementing space telescopes like Hubble and the soon to launch James Webb.
“Hubble's pictures have been fantastic, pioneering work.
But, they are somehow they've been pushed to their limit.
So, what I'm expecting is this 30 meter telescopes to do exactly the same revolution, as Hubble
did 20 years ago.”
But one major challenge these ground based scopes have to contend with is our planet’s
atmosphere.
“The problem is the light from the stars that's traveled for millions of years or sometimes
billions of years through the universe and through the galaxy, when it hits our atmosphere
the light kind of wiggles as it goes through.”
This is what gives the stars their classic twinkle, but it causes problems for astronomers
who want super sharp images.
This is where the next key advance comes in.
“Recently over the last ten years, there's been a lot of development, what is called
adaptive optics.”
Here’s how it works.
Lasers from the telescope are shot into space, exciting the atoms in the sodium layer of
the upper atmosphere and causing them to glow.
That glow acts as an artificial star that astronomers can use to calculate the amount
of atmospheric turbulence.
Then, the mirrors will flex and deform by computer controlled actuators to correct the
blur. “and, walla, you make sharp images.
The challenge is you have to do that 500 to 1,000 times a second and you have to do that
to about 1/20th of the wavelength of light in precision.”
With unprecedented light-collecting capability and advanced optical geometry, these new observatories
will tackle some of the most complex questions known to science.
“There's been a lot of recent discovery of exoplanets...We can see, more or less,
how distant they are from the planet.
But we would like to understand how they are made of.
Do they have an atmosphere which is similar to Earth, or not?
How do you form all these planets?
That's only one aspect.
Then, understanding how different galaxies formed and evolved across the cosmic time,
you know for 13.5 billion years.
And then, we can move to cosmology and understanding how dark matter and dark energy formed.
We are increasing the size so much, the capabilities are so powerful that it will open completely
new discoveries in space.
And we don't really know where they will take us, and that's to me the real beauty of this
new facilities.”
“Our telescopes while they might seem big they're really small compared to the size
of the earth or the size of the universe, so if we can collect more light, we have a
better chance of seeing those galaxies and black holes back when the universe was less
than one billion years old.
And that's one of our key drivers is to look back and see when did we transition from the
universe being dark, the end of the dark ages to the first time it lit up, what we call
cosmic dawn.
That's something that all astronomers would like to see and study the first light in the
universe.”
“The universe is a much bigger place than just what we experience here in our daily
lives on the earth, and it enriches our lives to simply understand that and to be aware
of it.”
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