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 | | NICOLAUS COPERNICUS |
| Poland (1473 - 1543) | Nicolaus Copernicus was the first astronomer to formulate a scientifically based heliocentric cosmology that displaced the Earth from the center of the universe. His epochal book, De revolutionibus orbium coelestium (On the Revolutions of the Celestial Spheres), is often regarded as the starting point of modern astronomy and the defining epiphany that began the Scientific Revolution. | | |
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Enjoy these insightful and educational video clips drawn from over 70 hours of interviews with the world's leading figures in astronomy, shot during the filming of 400 Years of the Telescope.
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Using adaptive optics to change the mirror shape
Taft E. Armandroff
- W. M. Keck Observatory
With Nelson’s vision and the advances in computer and sensor technology and actuator technology, we are using computers and sensors to constantly adjust the mirrors to compensate for the forces of gravity, to compensate for thermal effects and to adjust for everything that can keep the mirrors from being perfect.
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Well the older telescopes really relied on passive technology in order to compensate for how the mirror shape might change as the mirror pointed to different parts of the sky and the gravity vector was different on the mirror. With Nelson’s vision and the advances in computer and sensor technology and actuator technology, we are using computers and sensors to constantly adjust the mirrors to compensate for the forces of gravity, to compensate for thermal effects and to adjust for everything that can keep the mirrors from being perfect.
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Adaptive optics and the laser guide star
Taft E. Armandroff
- W. M. Keck Observatory
Adaptive optics uses a bright source coming from the atmosphere, originally a bright star to go out to something called a wave front sensor that tells us how the atmosphere is defocusing, introducing a stigmatism and other variables into this perfect star image that is hitting the upper atmosphere.
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Adaptive optics uses a bright source coming from the atmosphere, originally a bright star to go out to something called a wave front sensor that tells us how the atmosphere is defocusing, introducing a stigmatism and other variables into this perfect star image that is hitting the upper atmosphere. Originally this was requiring a bright star because we had to be able to sample the star two thousand times or more a second in order to correct for the timescales in the atmosphere. This wasn’t really practical because there weren’t enough interesting targets just near bright stars this was perhaps a half a percent of the whole sky was accessible in this manner. So we used sodium lasers to illicit a glow from the sodium layer in the upper atmosphere that is put there by micrometeorites.
We use a sodium laser to excite the sodium layer which is populated by micrometeorites up 90 km in the atmosphere. this creates an artificial guide star anyplace astronomers wanted in the sky, next to the most interesting object, next to the most distant galaxy, next to the star we suspect of having an earth-like planet. So we can use adaptive optics anywhere with this laser guide star technology.
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Extrasolar planetary search
Taft E. Armandroff
- W. M. Keck Observatory
You know Keck has been really active in discovering planets around nearby stars, and 20 years ago there were no planets known outside of our solar system. So I would predict the next great discovery with Keck is going to be a planet with a mass very similar to the Earth, and I think that is really going to galvanize not only astronomy community interest but public interest in habitable zones in planetary systems and in life elsewhere in the universe.
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You know Keck has been really active in discovering planets around nearby stars, and 20 years ago there were no planets known outside of our solar system. So I would predict the next great discovery with Keck is going to be a planet with a mass very similar to the Earth, and I think that is really going to galvanize not only astronomy community interest but public interest in habitable zones in planetary systems and in life elsewhere in the universe.
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Ground vs. space-based telescopes
Taft E. Armandroff
- W. M. Keck Observatory
Ground based telescopes offer a number of advantages over space-based telescopes. We are already getting resolutions with the Keck telescope that are significantly higher, two-to-four times higher, than with the Hubble space telescope.
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So ground based telescopes offer a number of advantages over space-based telescopes. We are already getting resolutions with the Keck telescope that are significantly higher, two-to-four times higher, than with the Hubble space telescope. This is because we have a larger mirror overall, and once we can use laser guide star adaptive optics to remove the blurring effects of the atmosphere we are limited by the size of the mirror. That’s what matters. So already we have a higher spatial resolution than space-based telescopes, but we also have a cost advantage from the ground where we can easily repair things by technicians. We can be more flexible to advances and things like detector technology, computer technology and we can tailor our science more rapidly to the best science questions of the day because ground based development simply takes less time and less cost than space-based development. So I think you’re going to see ground based telescopes in the future absolutely keeping up with developments in space.
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Why I became an astronomer
Taft E. Armandroff
- W. M. Keck Observatory
I got very interested in astronomy as a junior high school and high school student. I built a radio telescope in my own back yard. And I was very fortunate because my school district would send people to a place called Talcat Mountain science center during on the weekends where they would get people who were interested in science from a variety of schools, and pair them with scientists and engineers to work on special projects.
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I got very interested in astronomy as a junior high school and high school student. I built a radio telescope in my own back yard. And I was very fortunate because my school district would send people to a place called Talcat Mountain science center during on the weekends where they would get people who were interested in science from a variety of schools, and pair them with scientists and engineers to work on special projects. So that really stimulated me so by the time I went to university I knew I wanted to be an astronomer. I went to a small liberal arts school, Wesleyan University, where we had a great faculty in astronomy and great telescopes right there to could cut my teeth on. And I knew I was going to go to grad school in astronomy and it just continued in grad school at Yale. So I am very fortunate for the many mentors, scientists who took an interest in helping me over the years, and it has really helped me get to where I am today starting with from high school and on through college and grad school.
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Adaptive vs. active optics at Keck
Taft E. Armandroff
- W. M. Keck Observatory
Active optics compensate for slowly varying influences on the telescope optical system, so the mirrors and the mechanical systems that hold the mirrors into place. So these change rather slowly over the course of the night with the direction of telescopes pointed or with temperature.
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Active optics compensate for slowly varying influences on the telescope optical system, so the mirrors and the mechanical systems that hold the mirrors into place. So these change rather slowly over the course of the night with the direction of telescopes pointed or with temperature.
Adaptive optics is more breakthrough and really removes the effect that for all of our astronomical history has hampered astronomers. The effect of blurring from turbulent motions in our atmosphere and it compensates in a much more rapid dynamic timescale, two thousand times a second, to overcome the blurring effects of the atmosphere to make sure the stars don’t twinkle.
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Keck telescopes overview
Taft E. Armandroff
- W. M. Keck Observatory
The Keck telescopes are the two largest fully stirrable optical infrared telescopes in the world. They were the first of the new generation of large telescopes.
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Well the Keck telescopes are the two largest fully stirrable optical infrared telescopes in the world. They were the first of the new generation of large telescopes. They pioneered the use of segmented mirror technology which got us on the air sooner doing science than the monolithic mirror telescopes. We have also been extremely active in using adaptive optics to compensate for the blurring effects of the atmosphere and we have gotten images regularly that have more than twice to four times the resolution of the Hubble space telescope opening up whole new science areas for our community. We are now doing laser guide star adaptive optics that lets us do adaptive optics anywhere in the sky without the need for a bright natural guide star. This is being applied to a wide variety of problems from the black hole of the galactic center to planets around nearby stars, to the most distant galaxies in the universe.
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Astronomy answers at Keck
Taft E. Armandroff
- W. M. Keck Observatory
How do stars form and evolve? How does the galaxy form and evolve nearby galaxies? What are the real influences? What makes one galaxy a spiral and another an elliptical? What makes one star live a hundred thousand years and another live sixteen billion years?
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Well, it is extremely exciting to work on the big questions in astronomy. How does stars form and evolve? How does the galaxy form and evolve nearby galaxies? What are the real influences? What makes one galaxy a spiral and another an elliptical? What makes one star live a hundred thousand years and another live sixteen billion years? And many of these questions we’re actually finding out for the first time over the time period of my career. And I think all of us here at Keck observatory are thrilled that we can actually make a contribution to this. We are a fairly small organization and everybody makes a contribution to answering these questions. So it’s not only the scientists who are writing the papers, but it’s the electronic engineers who are developing the instruments, the mechanical engineers who keep the telescopes aligned, the technicians who keep it working every night so that the astronomers can use it on their targets and build up the signals. So it’s a wonderful team effort, and we all feel privileged.
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Segmented mirror technology
Taft E. Armandroff
- W. M. Keck Observatory
Jerry Nelson developed a revolutionary technique for instead of having one mirror as all telescopes had before Keck and following the prescription of say, the classic telescopes like the Palomar 200 inch, the Mt. Wilson 100 inch, and the Kitt Peak and Cerra Tololo four meters to make it much more achievable in terms of issues like weight, in terms of cost to break the mirror into segments.
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Well Jerry Nelson developed a revolutionary technique for instead of having one mirror as all telescopes had before Keck and following the prescription of say, the classic telescopes like the Palomar 200 inch, the Mt. Wilson 100 inch, and the Kitt Peak and Cerra Tololo four meters to make it much more achievable in terms of issues like weight, in terms of cost to break the mirror into segments. And this is revolutionary technology that wasn’t uniformly embraced by the community, and it took Jerry’s determination and his teams widely testing all of the concepts, and the support of the Keck foundation to really demonstrate this technology. And I don’t think it was really until we got the first images with the telescope that people fully bought into the technology. Now, it’s fully embraced, it is being used in other telescope projects currently and it’s thought to be the best technology for the 30 meter telescopes. So we are really pleased with the role Keck has played not only in the science, but also in the technologic revolution of telescopes.
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The 30-meter telescope
Taft E. Armandroff
- W. M. Keck Observatory
The 30-meter telescope plans to use segmented mirror technology just like Keck, and between Keck and 30 meter telescope we have a great interchange of technical knowledge on topics like controls systems, for keeping the mirrors precisely positioned, working on illuminizing the segments and adaptive optic systems.
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The 30 meter telescope plans to use segmented mirror technology just like Keck, and between Keck and 30 meter telescope we have a great interchange of technical knowledge on topics like controls systems, for keeping the mirrors precisely positioned, working on illuminizing the segments and adaptive optic systems. So we very much view this next generation of telescopes, particularly the 30 meter telescope, as the next chain in the evolution of the telescope.
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