EDWIN POWELL HUBBLE

Edwin Powell Hubble 1889-1953

Edwin Powell Hubble was an American astronomer born November 20, 1889.
Hubble spent his early years in Kentucky before going to Chicago, where his father, a lawyer, works in insurance. At school, Hubble proved a very good student and a first-class athlete.
He won a scholarship to attend the University of Chicago, where Hale and Millikan work that will influence him. Very good heavyweight boxer, he earned a degree in mathematics and astronomy.
In 1910 he went to Oxford to study law rather than mathematics that is too specialized.
He continues to fight in the show. Back in the United States in 1913, he was admitted to the bar and opened an office in Louisville, Kentucky.
In 1914 he began university studies at the Yerkes Astronomical Observatory in Wisconsin, founded by George Ellery Hale.
In 1917 he obtained his doctorate with a thesis research on nebulae, in which he concludes that the planetary nebulae in our galaxy, but the spirals are outside the Galaxy.
During a visit to Yerkes, impressed by the talents of Hubble observations, Hale offered him a position at Mount Wilson telescope equipped with a 1.5 m Hubble sends a telegraph to Hale, "I wish I could accept your invitation. I'm leaving for war." It serves the American expeditionary force in France until the fall of 1919.
Back in the U.S., he soon joined Hale at Mount Wilson.
His arrival at Mount Wilson more or less coincides with the completion of the Hooker telescope of 250 cm, the most powerful telescope at the time. The observations made with the Hubble telescope in the 1923 to 1924 to establish that the nebulae observed previously with less powerful telescopes are not part of our Galaxy.
Using the law of Leavitt-Shapley, it determines the distance of M31, which he estimated at 800,000 light years, which puts it outside our galaxy.

Thus ends the Hubble long debate about the nature of diffuse objects is now known as galaxies. Now the boundaries of the observable universe away accordingly.
In 1929, Hubble analyzing the radial velocities of galaxies, measured by Slipher from shifts of spectral lines. It is limited to the first galaxies to less than 6 million light years and see that the velocity-distance relationship is approximately linear.
Along with Milton Humason, he extended his study of distant galaxies 100 million light years. The relationship is a straight line. He states his famous law.
"The galaxies are moving away from each other at speeds proportional to their distance."
In other words, more, a galaxy is far from us, more it seems to move away quickly. He created the concept of expansion of the Universe.
Galaxies are receding, but it's not a true motion of galaxies is that the Universe expands and gives the apparent velocity of galaxies. It is the space between galaxies increases, in fact it is the space-time expands. The concept is quite difficult to grasp.
His public lectures on topics as diverse as space exploration, Francis Bacon, science in England during the Renaissance, the smog, the telescope on Mount Palomar...
Edwin Powell Hubble died of a cerebral thrombosis September 28, 1953.

NB: the relation between redshift and distance of galaxies was already present linearly expressed in a 1927 article, written by Georges Lemaître.
However, Georges Lemaître uses for his discovery, observations on the distances of some galaxies from Hubble's work.

Image: Edwin Powell Hubble, Franklin Medal (1939), Gold Medal of the Royal Astronomical Society (1940).

Hubble diagram

The Hubble diagram was established in 1929, based on analysis of the radial velocities of galaxies, measured by Slipher Vesto from redshifts of spectral lines. It represents the speed of galaxies according to their distance, i.e. more a galaxy is from us, more it seems to move away quickly. It is from this study that the concept of expansion of the universe appears. The rate of expansion of these galaxies is the Hubble constant (Hο) calculated by Edwin Hubble and George Lemaitre in 1930. This discovery permits go back to the Big Bang and give an age to the observable universe which at the time was estimated to be between 12 and 14 billion years. Universe in 2013 according to the analysis more detailed, of the Planck telescope is old 13.8 billions years.

The inverse of the Hubble constant is called the "Hubble time" it is the time since the Big Bang, so the age of the universe. Hubble stated in 1929, his famous law: "The galaxies are moving away from each other at a speed proportional to their distance."

Image: the Hubble diagram represents the speed of galaxies according to their distance, i.e. more a galaxy is from us, more it seems to move away quickly. It is from this study that the concept of expansion of the universe appears. Credit NASA.