Heroes of Space: Edwin Hubble

How one of the world’s greatest astronomers shaped our understanding of the universe

Edwin Hubble is seen here using the 100-inch Hooker telescope at Mount Wilson in 1923. Image Credit: NASA

Edwin Hubble discovered many galaxies by the end of the 1920s and was able to piece together a classification system, known as the Hubble Tuning Fork diagram. Image Credit: NASA

Edwin Powell Hubble was born 20 November 1889 in Marshfield, Missouri, USA. He moved to Illinois in 1900 and was an athletic youth who favoured sports over science, becoming a gifted athlete in various sporting pursuits including baseball and basketball.

He was a strong student academically as well, and in 1910 he graduated from the University of Chicago with a bachelor of science degree, his studies having focused on mathematics, astronomy and philosophy. He then travelled to England where he spent three years at The Queen’s College, Oxford, before returning to his family’s new home in Kentucky to care for his mother and siblings following the death of his father in 1913.

Hubble’s father had long requested that he practise law over science, and Hubble had done so until his return to the USA, when he found his interest in law waning. At the age of 25, after a brief stint as a teacher, he decided to focus his efforts on becoming a professional astronomer. By 1917, he had received a PhD in astronomy from the University of Chicago after studying at the Yerkes Observatory.

The completion of his PhD was hastened, however, as Hubble would soon volunteer for the army when the United States declared war on Germany in World War I, quickly rising to the rank of major. Following the end of the war he picked up his studies of astronomy in Cambridge for a year before being offered a position at the Mount Wilson Observatory near Pasadena, California.

At Mount Wilson he was given access to a newly built 100-inch (2.5-metre) telescope, the most powerful in the world at the time, called the Hooker telescope. In 1923, he trained the telescope on a particularly hazy patch of the sky that appeared to be a star cluster in our galaxy. However, measuring the distance to this cluster, he realised that it was not a part of the Milky Way but an entirely new galaxy that we know today as the Andromeda Galaxy. This would be one of Hubble’s most groundbreaking discoveries.

Hubble realised that there are galaxies outside of the Milky Way when he observed the Andromeda Galaxy. Image Credit: Adam Evans

Hubble realised that there are galaxies outside the Milky Way when he observed the Andromeda Galaxy in 1923. Image Credit: Adam Evans

Up until that moment, it had been thought that the Milky Way was the extent of the cosmos. However, Hubble’s discovery that we were just one of many more galaxies, later calculated to number in the billions, completely changed our understanding of the universe. Hubble found galaxies of differing sizes and distances that challenged our preconceptions of the cosmos. It was akin to finding that the Solar System was not the extent of space, or that the Earth was not flat; we were but a small part of a small system in a small galaxy in a giant universe.

Towards the end of the Twenties Hubble had discovered enough galaxies that he was able to compare them to one another and create a classification system, known as the Hubble Tuning Fork diagram, which grouped galaxies into ellipticals, spirals and barred spirals.

Together with his colleague Milton Humason, Hubble studied the spectra of 46 galaxies to make a further groundbreaking discovery, namely that the galaxies were all moving away from us, with those further away moving the fastest. He correctly deduced that this was due to the universe expanding. He estimated the expansion at 500 kilometres (310 miles) per second per megaparsec (one megaparsec being about 3.26 million light years), a value known as the Hubble Constant that we are still refining today, although we now know it to be much less.

Hubble’s contributions to astronomy and our understanding of the universe were astounding. He passed away on 28 September 1953 in San Marino, California, but his legacy lives on in numerous ways, no more so than NASA’s Hubble Space Telescope that launched in 1990, named after the great astronomer himself.

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