HILO — Thanks to a new instrument at Gemini Observatory, astronomers have learned more about a planet nearly 2,000 light-years from Earth.
Alopeke, a survey instrument installed at Gemini in 2017, allowed astronomers to identify which of three stars a distant planet orbits around, providing insight into the behavior and properties of the planet.
The Kepler-13 star system is a triad of stars about 1,700 light-years from earth, around which one exoplanet was discovered orbiting in 2011. However, because of limitations in imaging technology, astronomers were unable to determine which of the three stars the planet actually orbits.
“The whole thing just looked like a blob,” said ‘Alopeke instrument scientist Andrew Stephens.
Alopeke — whose name means “fox” in contemporary Hawaiian — gathers thousands of very brief exposures — 60-milliseconds each, or less than one-tenth of a second — in order to mitigate image distortion caused atmospheric turbulence, in a process known as “speckle imaging.”
“The problem with speckle imaging is that, because the exposure is so brief, it only works for really bright objects,” Stephens said. “Unless, of course, you have a really big telescope like Gemini.”
With Alopeke and Gemini, Steve Howell of the NASA Ames Research Center was able observe the planet — Kepler-13b — passing in front of the three stars last year and used those data to determine that the distant planet — designated Kepler-13b — orbits around the brightest of the three stars, Kepler A.
“When we measure a planet’s properties, we measure them based on the properties of its star,” Stephens said.
By determining which star Kepler-13b orbits, Howell’s team learned more about the nature of the planet, which is the fifth-largest exoplanet ever discovered. The planet is now believed to believed to be a “hot Jupiter,” a gas giant with an extended atmosphere similar to Jupiter in our solar system, but orbiting close to its star.
This is the first time an object in orbit around a multi-star system has had its orbitee identified. About one half of all exoplanets discovered exist in such systems.
“Our work with Kepler-13b stands as a model for future research of exoplanets in multiple star systems,” Howell continued. “The observations highlight the ability of high-resolution imaging with powerful telescopes like Gemini to not only assess which stars with planets are in binaries, but also robustly determine which of the stars the exoplanet orbits.”
Email Michael Brestovansky@hawaiitribune-herald.com.