One of the great delights in reading historical fiction is teasing out fact from invention, a pleasure accentuated by the central theme of Michael Byers’s latest novel, “Percival’s Planet.’’ In this quietly poignant book about the search for Planet X (eventually known as Pluto), all of the fictional characters orbiting Clyde Tombaugh, the astronomer who discovered Pluto, are in some way navigating that thin and shifting border between what’s literal and imagined, between what’s real and simply longed for.
At the start of the 20th century, wealthy Boston astronomer Percival Lowell, founder of Arizona’s Lowell Observatory, speculated that shifts in the orbits of Neptune and Uranus could be explained by the gravitational pull of an unseen planet in our solar system, so he searched the skies for it. The story opens in 1929, years after Lowell’s death, as the fictitious Alan Barber, a Harvard-educated astronomer, son of a widowed schoolteacher, continues Lowell’s pursuit, performing the nightly grunt work of photographing a small region of the sky, then comparing the configuration of visible objects with the same section of sky photographed two weeks later.
