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10. Big Glass
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Astronomy: Exploring Time and Space
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The Tools of Astronomy
A continuing revolution in telescope design and construction is giving astronomers an unprecedented set of tools for exploring the universe.
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Chris ImpeyDistinguished Professor
Astronomy
Let's talk about the big glass that astronomers are building for
our next generation of telescopes.
The LSS team Mirror is sturdy enough that you can sit on it as
you can see in this picture.
Also, it's huge, it's a size of your living room or larger.
Not just telescopes on the ground but
telescopes in space are attaining new heights.
The frontier for Space Astronomy will be the James Webb Space Telescope.
The successor to Hubble.
Time and cost over runs means that the Hubble will
die before the James Webb Telescope is likely to be launched, but James Webb will
eclipse Hubble in it's size, being six and a half meters in diameter.
James Webb is an extremely challenging design.
The mirror will essentially unfold once it reaches it's
location a million miles from the Earth.
This is so far from the Earth it is unserviceable by astronauts.
This telescope has to work perfectly and
correctly, because it can't be fixed if anything goes wrong.
That's very high-stakes for a space mission.
The mirror unfolds when it's situated at its proper location, and
the instruments deploy.
There's a sunshade and solar panels as usual to get power from the sun.
The individual mirrors are hexagonal elements.
All of these have been fabricated and have reached their specification.
James Webb's instruments have been tested on the ground and
in a vacuum in labs on the ground, and all have met their performance specs.
The James Webb Space Telescope is almost ready to fly.
James will vault Space Astronomy into a new regime.
The Hubble Space Telescope is 2.4 meters in diameter,
about as far as your arm span will reach in either direction.
The Spitzer Space Telescope,
a wonderful infrared facility is even smaller, less than a meter across.
James Webb vaults above these two facilities with ten
times more collecting area, and it will indeed see to the dawn of time.
In part, because life in the distant Universe is red-shifted or
shifted by cosmic expansion to longer wavelengths.
The James Webb Telescope concentrates on a different spectral region than
the Hubble Space Telescope.
Hubble works in the ultraviolet throughout the visible range and
into the near infrared.
James Webb will not work in the ultraviolet, and
it will only work at the reddest of optical wavelengths.
Most of it's work will be at invisibly long wavelengths just beyond where
the eye can see.
The degree of technical challenge of the James Webb mission is extraordinary,
because of the complexity and
number of moving parts of the instrument in the telescope assembly.
And the fact that it must be deployed robotically and
remotely, far from the possibility of servicing or fixing by astronauts.
The engineers involved in this undoubtedly have had
sleepless nights worrying about whether their part of
the complex mechanism will work as advertised when launch comes.
We could hear from a NASA Administrator or a Chief Scientist about
the James Webb Space Telescope, but I think it comes better from a young person.
Anyone excited about the possibilities of space Astronomy will recognize that
James Webb is an extraordinary mission.
>> Here are the top five reasons why the James Webb Space Telescope.
Freaking kicks ass.
It is huge.
The total mirror size is seven and
half times larger than the Hubble Space Telescope's Mirror.
The heatshield is the size of a tennis court.
Number four, it is a freaking transformer.
So in order to fit into the rocket, it's super duper folded up.
And when it arrives it unfolds in like 12,000 different marvelous little ways.
That could go wrong in any moment, and it freaks me out because I worry about that.
Number three, it will operate 1 million miles from Earth.
That's about four times as far away from the Earth as the Moon is.
The Webb Telescope actually orbits the sun.
That's the simplification.
It's actually in the relative stationary of Sun-Earth to Lagrange point two.
Which I'm not going to try to explain to you right now.
If it screws up, there's no way to fix it.
One chance to do it right or it's a $6 billion piece of space junk.
That is tense.
Number two, it will be able to see planets orbiting stars in our galaxy.
Individual planets.
If the James Webb Space Telescope was 25 light-years away.
It could see the Earth.
They can also determine the chemical composition of planets, and
it can peer into stellar nurseries, to see planets as they form.
And finally, the James Webb Space Telescope can see 13.4 billion years
into the past.
We will be seeing the first galaxies as they form, the first stars as they form.
And guess what, none of this is necessary to life on Earth.
None of it's going to help us cure malaria and install a democracy in Egypt, but
it is awesome in the truest sense of the word awesome.
I'm sorry that there's so
many hand gestures in this video, [LAUGH] I'm feeling very gesture.
This is the dawn of everything that we know, and
that is increasing awesome, and that is something that I can get behind.
>> The James Webb Space Telescope will cover all of
Astronomy working on topics from planets to cosmology.
But it'll or may have a particular impact on two fields.
One is the study of distant galaxies.
Perhaps the primary focus of James Webb is going to be detecting first light in
the Universe.
This is a time, somewhat over 13 billion years ago, when the very first stars and
galaxies lit up in the Universe, which was cooling from a thin, diffused and
almost uniform gas.
This is impossible to observe with the Hubble Space Telescope.
It simply doesn't have enough light-gathering power, and
it works primarily in the visible range, not in the near infrared.
James Webb will also do work on characterizing exoplanets.
Exoplanets had not even been discovered when the James Webb was
first conceived of.
So this is new Science for that telescope.
But it will be able to do spectra of exoplanets to try and look for biomarkers.
That is the chemical signatures of life on a distant planet.
A very exciting project that is nonetheless extremely challenging even for
this large telescope.
James Webb is long overdue and over-budget and the price tag has caused some stress
to the astronomical community, as well as to NASA which manages this large project.
But James Webb has an almost firm launch date, somewhere around the end of 2016 or
early 2017, it's passed all of it technical hurdles and
astronomers are starting to anticipate it with pleasure.
That's big glass in space, what about on the ground?
We've seen examples of big telescopes that are being prepared at the University of
Arizona using our mirrors.
The largest single-dish at the moment is actually a non-steerable optical
telescope called the Grand Canary Telescope,
build by the Spanish in partnership with other organizations.
It's on the Canary Islands where there's a major observatory, and
this mirror can only stare at one strip of sky that passes overhead.
That allows the mirror and the telescope to be quite cheap.
Because no large structure is needed to steer around the sky.
[MUSIC] The next very large telescope to be
commissioned we hope will be the Giant Magellan Telescope.
A partnership between the University of Arizona and the Smithsonian Organization
and a set of private and public universities in the United States.
This telescope should be commissioned sometime late this decade.
It's going to be built on Alaskan Palace Observatory site where we
already have a pair of six and a half a meter telescopes.
This visualization of the structure shows the size and complexity and also
the ability to grasp light from across the Universe of this wonderful facility.
[MUSIC]
Even larger than the GMT and
in a sort of friendly competition with it, is the 30-meter telescope.
Which is being built by the Caltech and University of California Consortium.
There's a friendly rivalry here and
in fact, the world perhaps could do with a couple of these large telescopes since
there's plenty of Science to fuel more than one super-large telescope.
The TMT will almost certainly built either in Hawaii or also in Chile.
It's a 30-meter telescope, so
it's larger than the one that we plan and it will use the Mosaic Technology.
Essentially scaling out the uuu concept, rather than having single, large,
monolithic mirrors.
An animation of the very center of our galaxy shows the importance of
having these super-large mirrors with their diffraction limits realized by
the use of adaptive optics.
If you look at the seeing of standard monochaic sight, which is exceptionally
good, there's just a blur where the star cluster exists at Sagittarius A Star.
This is the dynamical center of the galaxy.
What astronomers want to do is track individual stellar motions over a period
of years, motions in the animation to deduce the mass of the central black-hole.
Separating out the motions of the stars implies resolving those stars, and when
they're a blurry mess, as is seen without adaptive optics, that's impossible.
The first step in this progression is the use of adaptive optics on
the ten-meter telescope.
This goes some way towards resolving a few dozen stars in
the galactic center whose motion can be tracked with time.
But to go beyond that with a 30-meter telescope in
adaptive optics increases the number of probes of the black-hole of
the galactic center from a few dozen to perhaps hundreds.
And these motions can be studied in exquisite detail.
When telescopes get very large,
astronomers essentially run out of things to call them.
The names almost get silly.
There's a telescope that originally was called the Overwhelmingly-Large Telescope,
OWL, and has been renamed the Extremely-Large Telescope,
which is a project of the European Southern Observatory.
The Consortium of countries based in Europe who's observatory is in
Chile in the dark skies and high-site just South of Las Campanas Observatory,
where our telescopes are located.
This project was supposed to be 100-meter diameter mirror.
If ever built at this size, it would rival the largest human objects made,
the Great Pyramid at Giza or
any of the big Cathedrals of classic Europe, an enormous structure.
Imagine a mirror the size of a football pitch pointing with a precision of
one part in ten to the seventh to any part of the sky in just ten seconds.
A phenomenal undertaking.
The reason to do this is the same as the reason to build any large telescope.
When coupled with adaptive optics, the hundred meter aperture gives you
even better angular resolution, turning a blurred mass of a star cluster into
the pinpoint of hundreds, or even thousands, of individual stars.
This exquisite imaging let's you answer scientific questions that
could not possibly be answered either without adaptive optics or
without a mirror of this size.
In the last few years, budget realities have set in,
in Europe as in the United States, and
the 100-meter telescope has been de-scoped to a mirror 42 meters.
However, the project is not yet fully funded.
When built, it would indeed, be the largest telescope in the world.
Astronomers' hunger for photons, to reach even deeper and
further into the Universe, is unquenched.
The biggest glass being contemplated in space is the James Webb Space Telescope,
which will be a worthy successor to the Hubble Space Telescope when
it's decommissioned in a few years.
Six and half meters in diameter, it will search for first light in the Universe.
Meanwhile, on the ground, telescopes ten, 20, 30, and even 40 meters are planned.
Ground-based observatories that will each cost well over $1 billion, and
will give unprecedented depth and scope.
When coupled with the technique of adaptive optics.
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