Polluted white dwarf stars—which host planetary debris like calcium, magnesium, and iron—are key in helping astronomers discover what's beyond our solar system. "The mechanism that creates the rings of planetary debris, and the deposition onto the stellar atmosphere, requires the gravitational influence of full-fledged planets," an expert explains in a release. In other words, they suggest the existence of planets too far away for our telescopes to see. Scientists only learned about these stars 12 years ago, shortly after the first planets beyond our solar system were discovered in the 1990s, which is why a new study has many feeling like they've just been hit by an asteroid, per Discovery News. It turns out the first evidence of planetary systems around a white dwarf was captured in 1917—more than 50 years before we set foot on the moon.
While researching an article about a white dwarf called Van Maanen's star, Jay Farihi of University College London surveyed a glass photographic plate in the Carnegie Observatories' collection—made by former director Walter Adams in 1917—which shows an image of the light the star emits. As Farihi discovered, it also shows evidence that the light passed through debris, suggesting an exoplanet is orbiting the star, report CNET and Gizmodo. Farihi says it's only a matter of time before astronomers discover it. "The unexpected realization that this 1917 plate from our archive contains the earliest recorded evidence of a polluted white dwarf system is just incredible," adds Carnegie Observatories' director. "We have a ton of history sitting in our basement and who knows what other finds we might unearth in the future?" (This is the biggest known structure in the galaxy.)