History: How Hubble Came About
The Earth's atmosphere is the bane of astronomers. The idea of sending a telescope into space to avoid it was first proposed long before the first satellites were launched, long before anyone even dreamt of sending astronauts to space.
German rocket scientist Herman Oberth was a pioneering thinker of his time and suggested a space bound telescope as early as 1923 in his book "Die Rakete zu den Planeträumen". A space telescope avoids frustrating problems such as cloudy and misty observing nights, the twinkling of stars even on clear nights and absorption of the ultraviolet and infrared parts of the spectrum.
It took many years before technology caught up with Oberth's idea. The American Lyman Spitzer proposed a more realistic plan for a space telescope in 1946 and lobbied for his idea for almost 30 years. In the 1970s NASA and the European Space Agency took up the idea and proposed a 3 metre space telescope. Funding began to flow in 1977 and it was decided to name the telescope after Edwin Powell Hubble who had discovered the expansion of the Universe in the 1920s. Although the Hubble Space Telescope was down-sized to 2.4 metres the project started to attract significant attention from astronomers.
The precision-ground mirror was finished in 1981 and the assembly of the entire spacecraft was completed in 1985. The plan called for a launch on NASA's Space Shuttle in 1986, but just months before the scheduled launch the Challenger disaster caused a year long delay of the entire Shuttle programme. Hubble was finally launched in 1990 and the tension built up as astronomers examined the first images through Hubble's eyes.
As in all good adventures, success does not come easily: it did not take more than two months to realise that Hubble's mirror had a serious flaw. A focusing defect prevented Hubble from taking sharp images - the mirror edge was too flat by a mere fiftieth of the width of a human hair. Over the next months scientists and engineers from NASA and ESA worked together and came up with a superb corrective optics package that would restore Hubble's eyesight completely.
A crew of astronauts carried out the repairs necessary to restore the telescope to its intended level of performance during the first Hubble Servicing Mission (SM1) in December 1993. Although the two subsequent servicing missions were at least as demanding in terms of complexity and workload, SM1 captured the attention of both astronomers and the public at large to a degree that no other Shuttle mission since has achieved. Meticulously planned and brilliantly executed, the mission succeeded on all counts. It will go down in history as one of the highlights of human spaceflight. Hubble was back in business.
Since SM1 three other Servicing Missions have been carried out: during SM2 in 1997 two new instruments were installed, in SM3A, 1999, many of Hubble's crucial technical systems were exchanged, and in 2002 came SM3B when Hubble again got new science instruments.
The final planned Servicing Mission will be in 2008, when Servicing Mission 4 is scheduled to upgrade Hubble's scientific capabilities again.
The Man Behind the Name
"I knew that even if I were second or third rate, it was astronomy that mattered."
As a result of Hubble's work, our perception of mankind's place in the Universe has changed forever: humans have once again been set aside from the centre of the Universe. When scientists decided to name the Space Telescope after the founder of modern cosmology the choice could not have been more appropriate.
A promising student
Edwin Hubble was born in Missouri in 1889, the son of an insurance executive, and moved to Chicago nine years later. At his high school graduation in 1906, the principal said: "Edwin Hubble, I have watched you for four years and I have never seen you study for ten minutes." He paused, leaving young Edwin on tenterhooks a moment longer, before continuing: "Here is a scholarship for the University of Chicago."
This high school scholarship was also awarded to another student by mistake, so the money had to be halved and Edwin had to supply the rest. He paid his expenses by tutoring, working in the summer and, in his junior year, by obtaining a scholarship in physics and working as a laboratory assistant. He finally obtained a degree in Mathematics and Astronomy in 1910.
The Rhodes scholar
A tall, powerfully built young man, Hubble loved basketball and boxing and the combination of athletic prowess and academic ability earned him a Rhodes scholarship to Oxford. There, a promise made to his dying father, who never accepted Edwin's infatuation for astronomy led him to study law rather than science, although he also took up Literature and Spanish.
He studied Roman and English Law at Oxford and returned to the United States only in 1913. Here he passed the bar examination and practised law half-heartedly for a year in Kentucky, where his family was then living.
The beloved high school teacher and coach
He was also hired by New Albany High School in the autumn of 1913 to teach Spanish, Physics and Mathematics and to coach basketball. His popularity as a teacher is recorded in the school yearbook dedicated to him: "To our beloved teacher of Spanish and Physics, who has been a loyal friend to us in our senior year, ever willing to cheer and help us both in school and on the field, we, the class of 1914, lovingly dedicate this book."
When the school term ended in May 1914, Hubble decided to pursue his first passion and so returned to university as a graduate student to study more astronomy.
A new era for astronomy begins
The famous British astrophysicist Stephen Hawking wrote in his book A Brief History of Time that Hubble's "discovery that the Universe is expanding was one of the great intellectual revolutions of the 20th century." Who could have guessed such a future for Edwin when he began his PhD in Astronomy at Chicago University in 1914?
War postpones Hubble's astronomical debut
Early in 1917, while still finishing the work for his doctorate, Hubble was invited by George Ellery Hale, founder of the Mount Wilson Observatory, in Pasadena, California, to join the staff there. This was a great opportunity, but it came in April of a dreadful year. After sitting up all night to finish his PhD thesis and taking the oral examination the next morning, Hubble enlisted in the infantry and telegraphed Hale: "Regret cannot accept your invitation. Am off to the war."
He served in France and next returned to the United States in 1919. He went immediately to the Mount Wilson Observatory, where the newly discharged Major Hubble, as he invariably introduced himself, arrived, still in uniform, but ready to start observing.
Hubble was lucky enough to be in the right place at the right time. Mount Wilson was the centre of observational work underpinning the new astrophysics, later called cosmology, and the 100-inch Hooker Telescope, then the most powerful on Earth, had just been completed and installed after nearly a decade of work.
On the mountain Hubble encountered his greatest scientific rival, Harlow Shapley, who had already made his reputation by measuring the size of the Milky Way, our own Galaxy. Shapley had used a method pioneered by Henrietta Leavitt at the Harvard College Observatory that relied on the behaviour of standardised light variations from bright stars called Cepheid variables to establish the distance of an object.
His result of 300 000 light-years for the width of the galaxy was roughly 10 times the previously accepted value. However Shapley, like most astronomers of the time, still thought that the Milky Way was all there was to the Universe. Despite a suggestion first made by William Herschel in the 18th century, he shared the accepted view that all nebulae were relatively nearby objects and merely patches of dust and gas in the sky.
The turning point
Hubble had to spend many bitterly cold nights sitting at the powerful Hooker telescope before he could prove Shapley wrong. In October 1923 he spotted what he first thought was a nova star flaring up dramatically in the M31 'nebula' in the constellation of Andromeda. After careful examination of photographic plates of the same area taken previously by other astronomers, including Shapley, he realised that it was a Cepheid star. Hubble used Shapley's method to measure the distance to the new Cepheid. He could then place M31 a million light-years away - far outside the Milky Way and thus itself a galaxy containing millions of stars. The known Universe had expanded dramatically that day and - in a sense - the Cosmos itself had been discovered!
Even The New York Times of the day realised the importance of the discovery: "Finds spiral nebulae are stellar systems. Doctor Hubbel [sic] confirms view that they are 'island universes' similar to our own."
Just the beginning
This discovery was of great importance to the astronomical world, but Hubble's greatest moment was yet to come. He began to classify all the known nebulae and to measure their velocities from the spectra of their emitted light. In 1929 he made another startling find - all galaxies seemed to be receding from us with velocities that increased in proportion to their distance from us - a relationship now known as Hubble's Law.
This discovery was a tremendous breakthrough for the astronomy of that time as it overturned the conventional view of a static Universe and showed that the Universe itself was expanding. More than a decade earlier, Einstein himself had bowed to the observational wisdom of the day and corrected his equations, which had originally predicted an expanding Universe. Now Hubble had demonstrated that Einstein was right in the first place.
The now elderly, world-famous physicist went specially to visit Hubble at Mount Wilson to express his gratitude. He called the original change of his beloved equations "the greatest blunder of my life."
Another war stops Hubble again
Hubble worked on indefatigably at Mount Wilson until the summer of 1942, when he left to serve in World War II. He was awarded the Medal of Merit in 1946. Finally, he went back to his Observatory. His last great contribution to astronomy was a central role in the design and construction of the Hale 200-inch Telescope on Palomar Mountain. Four times as powerful as the Hooker, the Hale would be the largest telescope on Earth for decades. In 1949, he was honoured by being allowed the first use of the telescope.
No Nobel Prize for an astronomer
During his life, Hubble had tried to obtain the Nobel Prize, even hiring a publicity agent to promote his cause in the late 1940s, but all the effort was in vain as there was no category for astronomy. Hubble died in 1953 while preparing for several nights of observations, his last great ambition unfulfilled.
He would have been thrilled had he known that the Space Telescope is named after him, so that astronomers can continue to "hope to find something we had not expected", as he said in 1948 during a BBC broadcast in London.