The Andromeda "nebula," photographed at the Yerkes Observatory around 1900 is shown above. To modern eyes, this object is clearly a galaxy. At the time, though, it was described as “a mass of glowing gas,” its true identity unknown. Seventy-five years after this first image of Andromeda, NASA launched one of the most ambitious experiments in the history of astronomy: the Hubble Space Telescope, which has so radically changed and enlarged our picture and understanding of the cosmos and our place in it, is a cooperative project of NASA and ESA (European Space Agency), put into orbit in 1990 600 kilometers above the earth, allowing an unrivaled, undisturbed view into deep space.
Not by accident, the space-born telescope is named after one of the most fascinating men in the history of science. Born in 1889, ten years after Einstein (of whom he had little knowledge), few greats have had more effect on our knowledge of the cosmos than Edwin Hubble. A naturally-gifted track star, and scholar, the Missouri-born Hubble spent his life following a doctorate in astronomy from the University of Chicago answering two of the most fundamental and profound questions about our universe: how big is it, and how old?
The number of known galaxies at the time he first looked out to the cosmos from Mt Wilson was exactly one: the Milky Way. The Milky Way was thought to embrace the entire cosmos with everything else, distant puffs of celestial gas.
Hubble's great breakthrough came in 1923 when with a fresh eye he showed that a distant cloud of that peripheral celestial gas in the Andromeda Constellation known as M31 wasn't a gas cloud, but a maze of brilliant stars, a "nebulae" (Latin for "cloud") -a galaxy a 100,000 light years across and at least 900,000 light years distant from Earth.
This discovery led to his 1924 research paper "Cephids in Spiral Nebulae" (Hubble's term for galaxy) showing that the universe -which we now know houses some 130 billion galaxies- was made up of not just the Milky Way, but a myriad of "island universes," many far more distant and larger.
Hubble then turned to the next question of equally cosmic proportions,just how big is the universe, and made an equally striking discovery: that all the galaxies except for our local cluster are moving away from us at a speed and distance that are nearly proportional. In short, the more distant the galaxy, the faster it was moving.
The concept of an expanding universe destroyed the old, longstanding notion of a static steady-state universe, the wonder of which Stephen Hawking has exclaimed, was that it wasn't obvious before that a static universe would have collapsed in upon itself.
Hubble's ignorance of Einstein's General Theory of Relativity led to his nor being able to connect the dots between a universe that was expanding evenly in all directions (the "Hubble Constant") to a geometrical starting point, a "primeval atom, a Big Bang. That answer came several decades later with the discovery of cosmic background radiation from a hissing, constant, uniform low-frequency radio signal at a Bell Labs facility in rural New Jersey.
The Daily Galaxy via Yerkes Observatory, Hubble.org and ESA
Image credit top of page: With thanks to Astronomy of To-Day, 1909