The first ever evidence of an exoplanet was taken during World War One, it has emerged, decades before their existence was confirmed.
Dutch-American astronomer Adriaan van Maanen took a series of spectra images of the light emitted by different stars in 1917, in which he discovered a white dwarf – which is a dead star.
The images were recorded on glass photographic plates at California’s Carnegie Observatories, but filed and forgotten.
At the time, no-one realised that the image also showed evidence of one or more exoplanets – worlds orbiting a star other than our Sun.
It had been previously thought that the first detection of exoplanet evidence was made in 1992.
The chance discovery of the 1917 slide’s significance was only made after Jay Farihi, from University College London, recently contacted the Carnegie Institution for Science.
He wanted the glass plate showing the white dwarf – named van Maanen 2 – as part of a study of planetary systems surrounding such stars.
On examining the spectrum, he found clues which showed that the white dwarf was “polluted”, meaning that it likely has the rocky remnants of a planet or planets orbiting it.
Observatories’ director John Mulchaey said: “The unexpected realisation that this 1917 plate from our archive contains the earliest recorded evidence of a polluted white dwarf system is just incredible.
“We have a tonne of history sitting in our basement and who knows what other finds we might unearth in the future?
“The mechanism that creates the rings of planetary debris, and the deposition onto the stellar atmosphere, requires the gravitational influence of full-fledged planets.
“The process couldn’t occur unless there were planets there.”