Lyman Spitzer and the Space Telescope
Part of the Cosmic Horizons Curriculum Collection.
In the case of the Hubble Space Telescope, arguably the most successful and celebrated scientific instrument ever built, it took fifty years from conception to full realization. The most important champion of the project was Lyman Spitzer.
Spitzer (1914–1997) studied astronomy at Yale, Cambridge, and Princeton University. During World War II, he worked on the development of sonar. In 1947 he succeeded Henry Norris Russell as Chair of Princeton’s Astrophysical Sciences Department. During a long and productive career, Lyman Spitzer shaped three major fields of astrophysics—interstellar matter, plasmas, and the dynamics of star clusters. His work on interstellar matter began when he noticed that elliptical galaxies have only old stars and no nebulas of gas and dust, while spiral galaxies include young stars and nebulas. He realized that stars must now be forming in spirals from the gas and dust of the nebulas. Spitzer went on to establish the field of interstellar matter as a major branch of astrophysics.
But his greatest legacy is the Space Telescope. The idea of putting a telescope in orbit, above the obscuring veil of the Earth’s atmosphere, had been suggested as far back as 1923 by the German rocket pioneer Hermann Oberth. But rockets in those days were feeble and uncontrollable devices. Then, during World War II, the Germans developed the V-2 weapon, a powerful ballistic rocket which left the atmosphere in order to come down on a distant target. It opened the way for the rocket-powered transport of payloads into space (including instruments and telescopes instead of bombs). Spitzer recalled in a discussion about the Space Telescope that the V-2 rockets “made it all seem possible.”
In 1946, Spitzer wrote a report for the RAND Corporation on “Astronomical Advantages of an Extra-Terrestrial Observatory,” in which he explored the advantages of a space-based telescope of five to fifteen meters in diameter. At the time of this astonishing proposal, the Palomar 5-meter telescope, then the largest in the world, was still under construction. And it was on an accessible mountaintop, not in orbital space. In his report, Spitzer said that the best reason to build a space-based telescope would be to “uncover new phenomena not yet imagined, and perhaps to modify profoundly our basic concepts of space and time.”
Spitzer described two major advantages of a space telescope. First, the atmosphere absorbs almost all the ultraviolet and most of the infrared light from space before it reaches the ground. Observations at such wavelengths must necessarily be made above the atmosphere. Second, the turbulence of the atmosphere blurs the images of celestial bodies. For example, the Palomar 5-meter telescope could in principal resolve images as sharp as 0.02 seconds of arc (like a penny seen from 120 miles away), a limit determined only by the diameter of the telescope. But in reality, atmospheric turbulence limits the sharpness of these images to about 1 second of arc. For comparison, the human eye can resolve images as small as 60 seconds of arc (1/60th of a degree). So the resolution of the Palomar telescope is only 60 times better than the human eye, but if placed above the atmosphere, it would be 3,000 times better. If astronomers could put a telescope in orbit, they would finally realize the full power of the telescopes they had been using for hundreds of years. Images of such clarity and precision had never been obtained.
In 1957, the Russians launched the first artificial Earth satellite, which stimulated the creation of the National Aeronautics and Space Administration the following year to promote the exploration of space. NASA began experiments with Orbiting Astronomical Observatories (OAOs), small satellites that would make limited observations. But the Apollo lunar landing project absorbed most of NASA’s resources and orbiting telescopes were given low priority and had little success.
After the successful lunar landing program, NASA began a modest study project for a Large Space Telescope (or LST, fondly referred to as Lyman Spitzer’s Telescope). In 1977 Spitzer and the astronomer John Bahcall took up the challenge of winning the necessary political support for the project. They traveled the country, convincing first their colleagues, then congressmen, and NASA headquarters, that a space telescope would be one of the greatest triumphs of astronomy.
Setbacks abounded, but their lobbying efforts slowly built up the necessary support. Once the project began in earnest and actual hardware was built, the payoff was enormous. Not only did the telescope make the most precise observations of the universe ever recorded, but technological advances tied to the project resulted in the improvement of commercial digital cameras and video recorders.
The Space Telescope was finally launched in April 1990, after a long delay following the explosion of the Space Shuttle Challenger in 1986. But when the first images were transmitted to the ground, there was a terrible disappointment. The images were blurred and showed the telltale signs of a failure in optical design. The 2.4–meter primary mirror had been crafted with exquisite accuracy but to the wrong shape! Fortunately the telescope had been designed for service visits by astronauts, and Spitzer contributed a level of optimism after this apparent disaster. He said calmly, “These things take time. We’ll just have to fix it.” The next Shuttle trip to visit the telescope carried a set of corrective optics which, when installed, allowed the Space Telescope to fully realize its goals.
Since then, the Hubble Space Telescope, named in honor of Edwin Hubble, discoverer of the extragalactic universe, has made impressive discoveries in many branches of astronomy. It has contributed to our understanding of the large-scale structure of the universe, and of stellar evolution and the dynamics of galaxies.It has produced firm evidence for black holes, and provided images of objects and phenomena not even imagined in the 1940s. Lyman Spitzer was right when he predicted that the Space Telescope would profoundly affect our conception of the universe. A gentle and graceful man, loved by all who knew him, Spitzer lived to see the marvelous images produced by the fully operational Space Telescope that was his brainchild.