Carnegie Institution
Photographic plate from 1917 with the spectral lines of van Maanen’s star (above), and annotations by the astronomer who observed itCarnegie InstitutionA glass photographic plate from 1917 holds the earliest known record to date of a planetary system distant from the Sun. The material was kept for nearly a century among the 250,000 plates in the collection at the Carnegie Observatories in the United States, and it has now been reanalyzed by astronomer Jay Farihi of University College London. Farihi was preparing a review paper on the evolution of disks formed by planetary debris around white dwarfs, stars in the final stage of life. These disks, the astronomer says, are evidence that the stars were once orbited by planets. Farihi asked officials at the Carnegie Observatories to locate the photographic plate of a star discovered in 1917 by Dutch astronomer Adriaan van Maanen. The plate shows two thick dark streaks, along with a third, slender one. The thinner streak is the spectral line of light emitted by the star, and it contains indications of the star’s chemical composition and that of objects that pass in front of it. According to Farihi, the line indicates the presence of heavy chemical elements, such as calcium, magnesium and iron, which in recent years have been associated with the existence of a planetary system with vast rings of rocky debris (New Astronomy Reviews, April 2016).
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