MOUNTAIN VIEW, CaliforniaPlanets orbiting other stars are running out of ways to hide.
For the first time, astronomers have used reflected starlight to tease out the possible presence of 60 large, roasted worlds. As those planets traipse around their stars, they act like large alien mirrors and briefly bounce a bit of extra starlight toward Earth, causing a small but measurable increase in their systems’ brightness.
The discoveries still need to be independently confirmed using a different planet-hunting method. But if even some of the worlds are really there, they could have an important story to tell about how such hot, Jupiter-size planets form.
“You see a brightening when the planet moves behind the star because at that point, you’re seeing its day side,” says Yale University graduate student Sarah Millholland, who will present the work Friday at the Kepler and K2 Science Conference.
The 60 possible planets were hiding among nearly 200,000 stars in the patch of sky that NASA’s Kepler spacecraft stared at for four years. Though the spacecraft has spotted more than 2,300 confirmed worlds among those stars, it can’t see all of the ones that must exist.
That’s because the probe orbits the sun, and distant planetary systems ordinarily need to be aligned just right so that planets pass between their stars and the spacecraft. Kepler can then detect a planet as it briefly blots out a portion of its star’s light. However, this configuration only occurs for about 10 percent of hot Jupiters.
“With the transit method, we’re still biased to systems that are aligned in a particular way, which means we don’t have the ability to explore the vast majority of planets in the galaxy,” says Caltech’s Courtney Dressing. “Sarah has found a way to identify more planets, even those in systems that are misaligned.”
The catch: Those planets need to be either really big, or really shiny.