Planet Hunters: The search for extraterrestrial life by Lucas Ellerbroek

Author:Lucas Ellerbroek [Ellerbroek, Lucas]
Language: eng
Format: mobi
Publisher: Reaktion Books
Published: 2017-07-31T16:00:00+00:00

‘WE HAVE no choice,’ Michel Mayor told his son. ‘I think we’re going to have to take you down a peg or two.’ During a holiday in Provence, Mayor and his friend and colleague Didier Queloz used code names for ‘that one star’. They talked about it a lot around the dinner table. The two families had redubbed the observation trip a holiday; the Observatoire de Haute-Provence was beautifully situated. Two white observatory domes reached out above the treetops in the undulating landscape. A short distance away were the sandstone houses of the village of Saint-Michell’Observatoire with their red roofs. The men spent their nights at the observatory. And now Mayor’s son had finally discovered the name of the mysterious star that had held his father in its grip for the whole holiday: 51 Pegasi.

Fortunately, nothing came of the plan to have the boy quietly disappear. Eighteen years later he is also a scientist, as are his two sisters. Their father Michel smiles at me from my computer monitor. The image of his friendly face, with a grey beard and glasses, is a little shaky on Skype. Mayor is an emeritus professor at the University of Geneva, where he has worked for almost fifty years. He started as a doctoral student and worked his way up to become director of the observatory. His retirement does not mean that he has stopped working. In the past year alone, he had co-authored more than twenty publications. The day after our conversation, he left for Vietnam to give an astronomy course to young people. While researching his PhD in the late 1960s, he developed theories about how the stars in the Milky Way move. He wanted to test those theories by measuring the velocities of stars. With the Doppler effect.

‘When we first started, no one was interested in measuring the speed of stars,’ he tells me. ‘You had to measure the tiny Doppler shifts in the spectrum by hand using the detector screen. But you could never achieve a decent degree of accuracy manually. It was an extremely dull and unsatisfying activity.’ At the end of the 1960s, he heard of a method that could be used to measure Doppler shifts much more quickly and accurately. The idea for the method had been formulated in 1953 by light expert Peter Fellgett, who said ‘If the only aim is to measure the Doppler shifts, it’s not necessary to observe all the details of the stellar spectrum.’

The secret was to use a special accessory on the spectrograph, a kind of template. It consisted of a glass plate coated with metal placed in front of the screen on which the stellar spectrum was projected. There were holes in the plate where absorption lines were expected. If the absorption lines had shifted, you had to move the plate to one side a little until the lines were completely aligned with the holes. That meant that you lost the rest of the information on the spectrum, but that was no problem as all Mayor wanted to measure was the speed of the star.

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