This a review of a free talk arranged by the Herne Hill Society. You can find out about our events programme here.
Astronomy was a popular pastime in Victorian times. We are aware of the telescope which was erected by Henry Bessemer in the garden of his house on Denmark Hill. At our November 2018 meeting Louise Devoy, Senior Curator at the Royal Observatory, Greenwich, came to talk about two other notable people in the field of astrophysics who lived in this area.
As a young man, William Huggins (1824–1910) had been forced to take over the running of his father’s draper’s shop, but he later decided to sell the family business and pursue his scientific dream, using the money to set up an observatory at his home at 90 Tulse Hill. His work helped revolutionise our understanding of the stars. The house was demolished in 1960 and there is a housing block on the site today. It was a rural location when Huggins bought his house in 1852. The observatory was an elevated structure, rising above the trees, separate from the main house, and built of iron and brick. Huggins installed an adjustable chair to enable him to match the changing height of the telescope eyepiece as he scanned the sky.
The stars were used mainly for navigation and timing. But in 1859 Bunsen and Kirchhof made a crucial breakthrough. Together they built a spectroscope, an instrument designed to measure the wavelengths of light emitted by an object. They used it to analyse sunlight and were able to identify two of the missing wavelengths associated with sodium, thereby concluding that sodium must exist in the sun’s atmosphere. They went on to search for evidence of other materials such as the heavy metals in the sun’s atmosphere. When Huggins heard about the spectroscopic discoveries he was overjoyed: “This news was to me like the coming upon a spring of water in a dry and thirsty land”.
Inspired by the work of his neighbour, chemist William Allen Miller, Huggins took the laboratory technique of spectroscopy and used it with his telescope to determine the chemical composition of the stars, and to analyse their motion through space. The two collaborated in analysing starlight using the spectroscope. In 1863 they presented their work to the Royal Society. During the 1860s Huggins applied spectroscopy to the stars beyond the Sun and confirmed that they too contained the same elements that existed on Earth: “a common chemistry it was shown exists throughout the universe”.
In 1875 Huggins met and married Margaret Lindsay Murray (1848–1915), 24 years his junior. Margaret was a keen photographer. She encouraged him to apply innovative photographic techniques to astronomy. Working together the couple continued to develop and publish their work throughout their lives. They produced the Photographic Atlas of Representative Stellar Spectra in 1900. When William was aged 84, he relied on his 60-year-old wife to clamber around the telescope and make the necessary adjustments. “Astronomers need universal joints and vertebrae of India rubber,” she complained.
Together, Mr and Mrs Huggins developed an entirely new application for spectroscopy, one that would transform our view of the universe. Their new technique could be used to measure the radial velocity of any star and it could be applied to even the most distant stars. The idea relied on coupling the spectroscope with Doppler’s discovery that when an object emitting waves moves towards an observer a decrease in the wavelength is observed, whereas when it moves away an increase in the wavelength is observed. In 1868 William and Margaret Huggins detected a Doppler shift in the spectrum of the star Sirius. They could therefore calculate the speed at which Sirius was receding from the Earth. Their method had huge potential because any visible star could be analysed with a spectroscope and thus have its Doppler shift measured and its velocity determined.
July 2019 is the 50th anniversary of the Apollo 11 moon landing, and a Moon Festival is planned for London “celebrating humanity’s relationship with the moon across cultures, time and disciplines”. Hopefully the part played by Mr and Mrs Huggins, working so close to Herne Hill, will be celebrated as a significant step in the scientific journey.
This a review of a free talk arranged by the Herne Hill Society. You can find out about our events programme here.
Val Suebsaeng
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