Date: January 31, 2009
Title: Beyond Vision
Podcaster: Chris Impey
Organization: Steward Observatory, University of Arizona
Description: In the 400 years since Galileo, astronomers have increased the light grasp of telescopes by a factor of ten billion. New technologies have allowed the creation of telescopes that would be unrecognizable to Galileo. They don’t use glass or mirrors or lenses and they often gather radiation that’s invisible to the eye. Astronomers have even managed to use the Earth as a telescope. These innovations have given us a sharper sense of the vast universe around us, of which we’re such a tiny part. By defining our relationship to the cosmos, the story of seeing the universe is really a story about us.
Bio: Chris Impey is University Distinguished Professor at the University of Arizona. As Deputy Head of Department and the Academic Head, he runs the nation’s largest undergraduate majors program in astronomy, and the second largest Ph.D. program. His research interests center in observational cosmology, gravitational lensing, and the evolution and structure of galaxies. He has 160 refereed publications and 60 published conference proceedings. His research has been supported by $18 million in grants from NASA and the NSF, and he has had 24 projects approved with the Hubble Space Telescope. He is a former Vice President of the AAS. His popular book on astrobiology, The Living Cosmos, was published by Random House in 2007.
Today’s Sponsor: This episode of “365 Days of Astronomy” is sponsored by Dale Thieme, in honor of his son, Brian, who has re-kindled in his dad a long dormant fascination with the night sky.
Transcript:
Introduce self: Professor of Astronomy, Univ. Arizona
Setup podcast: Celebrating 400 years of the telescope
Galileo’s Innovation
Galileo’s simple telescope, which can be reproduced today with a few dollars of components from a hardware store, turned the world inside out. Venus had phases so the Earth could not be at the center of the universe. The Moon had craters and so was a rugged geological world like our own. The gauzy light of the Milky Way was made up of myriad stars, and some were so faint that they must be millions of times more distant than the Sun. Galileo ran into the buzz saw of the Inquisition in daring to suggest that we were not the center of creation. Astronomy hasn’t looked back since, and we accept our place as inhabitants of an unremarkable planet orbiting a middle-weight star on the periphery of a typical spiral galaxy that we call the Milky Way.
Heirs to Galileo
The heirs to Galileo enhanced his legacy by the simple technique of using bigger and bigger lenses. This led to behemoths that trembled in the wind and registered the footfall of passing horses. Within the past century all major telescopes have been reflectors rather than refractors, and the largest mirrors approach the size of a small house. Here at the UA we make the largest mirrors in the world under the football stadium. The technology is casting large mirrors and polishing them is very refined. If our big mirrors were scaled up to the size of the continental United States, the largest departures for a parabolic shape would be just an inch high.
The progression from Galileo’s spyglass to the Hubble Space Telescope is a factor of ten billion gain in light grasp and a gain of a million in depth. Insatiable in their quest for distant light, today’s astronomers plan telescopes with segmented mirrors as big as a football field. Hubble’s great advantage stems from its vantage point above the blurring and the obscuration of the Earth’s atmosphere. But astronomers have been able to overcome much of the advantage of the space environment by using flexible optics to take out the image motion and jitter caused by the atmosphere. These methods let ground-based telescopes come close to the sharpest images that their optics will allow. With moderns CCDs, astronomers have almost perfect detectors; very few photons are wasted.
New technologies have allowed the creation of telescopes that would be unrecognizable to Galileo. They don’t use glass or mirrors or lenses and they often gather radiation that’s invisible to the eye. Astronomers have even managed to use the Earth as a telescope. These innovations have given us a sharper sense of the vast universe around us, of which we’re such a tiny part. By defining our relationship to the cosmos, the story of seeing the universe is really a story about us.
Beyond Vision
Optical astronomy is only good for studying stars. Since the universe contains about 40 billion galaxies, each of which has several hundred billion stars, that’s plenty to keep astronomers busy. But the universe contains violent and exotic phenomena that are best studied with the types of radiation that are invisible to the eye. This hidden universe has been seen only the radio, infrared, X-ray and gamma ray parts of the spectrum. These wavelengths have shown us black holes a billion times the mass of the Sun, particle accelerators that make our best efforts on Earth look feeble, and stars that in the moment of their cataclysmic demise outshine the entire universe. If the optical spectrum was represented by two adjacent notes on a piano, the entire electromagnetic spectrum is the full range of the piano, spanning gamma rays the size of an atomic nucleus to radio waves the size of a house.
Unusual Telescopes
In the past few decades, astronomers have developed ways of looking at the universe so unfamiliar that they’re barely recognizable as astronomy. We use the Earth as a telescope.
For example, solid state detectors on the ground detect the secondary air showers produced by high energy cosmic rays arriving at the top of the atmosphere. Some of them have the energy of a well-flung fastball and they may have been created in the environs of supermassive black holes many hundreds of millions of light years away. Strings of detectors lowered into melt holes in the Antarctic ice are being used to detect neutrinos from cosmic sources beyond the Sun.
The final frontier of astronomy is the detection of gravity waves. Almost everything we’ve learned about the universe has come from the detecting radiation and its interactions with matter. But if we could see with gravity eyes, we’d be able to directly view the force that gives the universe all its structure. A gravity wave observatory is starting operations in the northwestern US, with the goal of detecting neutron star and black hole interactions, and hopefully some of the exotic physics of the early big bang.
We even use the universe itself as a telescope-the big bang turns astronomers into armchair time travelers. Gravity can bend and focus light, and the phenomenon of gravitational lensing is being used to map out dark matter on the largest scales. It’s also being used to map out the shape of space itself. Four hundred years after Galileo’s innovation, we’re still finding new ways to explore the cosmos with telescopes.
365 Days of Astronomy
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