The giant Magellan telescope will be the first telescope to detect Earth-like
planets around distant stars, and we're going to learn more about this telescope
starting right now. Hi everyone, my name is Christian ready. I'm an astronomer and
I love to talk about this stuff, so if you are here for the first time please
make sure to hit the subscribe button and ring that notification bell icon so
you don't miss out on any new videos. The giant Magellan telescope or GMT as it's
called is one of the next generation of extremely large telescopes that are
currently under development. When it begins operations in 2023, it will be the
largest telescope we've ever constructed, and it'll be the first to image
Earth-like planets around distant stars. But let's talk a little bit about its
unique design. Giant telescopes like the Keck telescopes combine relatively small
mirrors to make giant 10 meter apertures. But breakthroughs in mirror technology
developed at the University of Arizona allows mirrors even larger than eight
meters to be created. In a previous video, I talked about the Large Synoptic Survey
telescope. It's going to use an 8.4 meter mirror that will make
LSST the largest single-mirror telescope ever built. But GMT will take a giant
leap forward by combining seven of these giant mirrors to create an enormous 25
meter mirror that's more than double the size of the largest telescopes in the
world today. But just having a large mirror isn't enough. Astronomical objects
are faint and their photons are few and far between.
That means the mirrors have to be perfectly shaped and aligned so they can
collect those photons and bring them to a focus. Any imperfection or even the
tiniest misalignment must be smaller than the wavelength of light itself. The
mirrors are built at the Richard F. Caris Mirror Lab at the University of
Arizona. A special low-expansion borosilicate
glass is placed into a honeycomb mold. The glass and mold are then enclosed in
an electric oven. The glass is heated to 1,200 degrees Celsius and melts into the
mold. While the glass is molten, the furnace spins to give the glass its
desired parabolic shape. The glass is then cooled very slowly at a rate of 3
degrees Celsius every day over a three-month period. Afterward, the glass
and mold are removed, the mirror is turned upright, and the mold material is
cleaned out. The result is a mirror that is 80% hollow and weighs a mere 20
tons. The mirror is then ground and polished to within 1/20th of the
wavelength of light. In other words, if just one of these mirrors were enlarged
to the size of the United States, its largest imperfection would be less than
a half an inch tall. Incidentally, the outer mirrors are off the optical axis.
So the inner edge of each mirror has to be a little thinner than its outer edge,
kind of like a giant glass potato chip. After polishing, an ultra-thin layer of
aluminum is applied. And by "ultra-thin", I mean just a few atoms thick! Each mirror
takes about four years to manufacture. The telescope will use seven mirrors and
eighth will act as a spare to be used whenever one of the mirrors are being
cleaned. But even under the clearest of skies, telescopes have to contend with
the distorting effects of the Earth's atmosphere. This is a phenomena called
astronomical seeing, and it's the reason we send telescopes like Hubble into space.
A telescope as large as GMT isn't going to find its way into space anytime
soon, but it does have a really cool trick up its sleeve. Its secondary
mirrors are thin and have actuators that warp and
deform them to correct for the effects of the atmosphere
in real time. This is called adaptive optics and GMT will have the most
advanced adaptive optics system ever developed.
Will it work? Well, let's imagine looking at a crowded star field under ideal
seeing conditions somewhere in the near infrared part of the spectrum. At this
magnification, the stars are just blobs of light. The Hubble Space Telescope, with
its 2.4 meter mirror, easily resolves the brightest of these stars.
And the James Webb Space Telescope, with an even larger mirror, will be able to
resolve some of the fainter stars. But the Giant Magellan Telescope, with its
large aperture and adaptive optics, will resolve all the way down to its own
diffraction limit. With that kind of resolution, GMT will be able to
investigate questions that astronomers have been asking for a very long time,
not the least of which is "are we alone"? GMT will be able to detect planets that
are more than 1 million times fainter than their host stars. We can do this
today with our current telescopes, but so far we're limited to planets that are
larger than Jupiter orbiting their host stars much farther away than Pluto (correction, Saturn) does
from the Sun. GMT however we'll be able to detect planets that are far closer to
their stars, maybe even as close as Earth is from the Sun. GMT we'll be able to
look at these planets' rotations, measure their masses, and even study their
atmospheres to see if they are capable of supporting life. And that's just one
of the questions GMT is designed to answer. It will also probe black holes to
understand how they work, and watch what happens as they destroy stars that
wander a little bit close. Or peer into the cores of distant galaxies, and watch
matter falling into the supermassive black holes at their center, creating
quasars. GMT will be able to help us better understand how stars form, and
even watch planets forming inside their planetary disks.
But the best thing about GMT is that it won't be alone. It will work in concert
with the next generation telescopes like James Webb, WFIRST, the Thirty Meter
Telescope, and the European Extremely Large Telescope. If you'd like to learn
more about these telescopes, I have some videos about them right here on this
channel, and I'll link to them in the description below. In the meantime, I'd
like to hear from you. What are you hoping we can learn about with the Giant
Magellan Telescope. What other upcoming telescopes or astronomical missions
are you excited about? Leave a comment below and I'll be sure to check it out.
And if you like this kind of stuff, make sure you subscribe and hit the
notification icon so you don't miss out on any new videos. Until next time, thanks
for watching, and keep watching the skies