Overlooked Treasure: The First Evidence of Exoplanets

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- editor by Tony Greicius

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This article from NASA tells about Hubble and Milton Humason began as a janitor, worked together to explore the expanding nature of the universe. Using the legendary telescopes, they recognized the clusters of galaxies are traveling away from each other and the more distant galaxies move away from each other at greater speeds, but there is a far lesser known, 100-year-old discovery from Mount Wilson, one that was unidentified and unappreciated until recently. It's actually: The first evidence of exoplanets.

It started with Ben Zuckerman, professor emeritus of astronomy at the University of California, Los Angeles. He was preparing a talk about the compositions of planets and smaller rocky bodies outside our solar system for a July 2014 symposium at the invitation of Jay Farihi,  While preparing his talk, Zuckerman had what he later called a "true 'eureka' moment." Van Maanen's Star, unbeknownst to the astronomers who studied it in 1917 and those who thought about it for decades after, must be the first observational evidence that exoplanets exist. Farihi had suggested that Zuckerman talk about the pollution of white dwarfs, which are dim, dense remnants of stars similar to the Sun that have exhausted their nuclear fuel and blown off their outer layers. But in 1987, more than 70 years after the Mount Wilson spectrum of van Maanen's Star, Zuckerman and his colleague Eric Becklin reported an excess of infrared light around a white dwarf. This was, in 1990, interpreted to be a hot, dusty disk orbiting a white dwarf. Inspired by Zuckerman, Farihi became enamored with the idea that someone had taken a spectrum with the first evidence of exoplanets in 1917, and that a record must exist of that observation.

Scientists are still exploring polluted white dwarfs and looking for the exoplanets they may host. About 30 percent of all white dwarfs we know about are polluted, and Farihi was thrilled about how his Mount Wilson archive detective work turned out. In 2016, he described the historical find in the context of a review paper about polluted white dwarfs, arguing that white dwarfs are "compelling targets for exoplanetary system research." Who knows what other overlooked treasures await discovery in the archives of great observatories -- the sky-watching records of a cosmos rich in subtlety. Surely, other clues will be found by those motivated by curiosity who ask the right questions.

by Dini Dwintika Karuniati

16611042

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