Gravitational lensing hunts for exoplanets around binary stars
Gravitational lensing hunts for exoplanets around binary stars lead image
Hunting for exoplanets is far from easy. Large planets close to their host stars can be spotted using the transit method and measuring the periodic dips in the star’s brightness, but for smaller or more distant planets, other techniques are required. One such method involves gravitational lensing, observing the light from a background star as it is distorted by the exoplanet’s system in the foreground.
George et al. explored the effects of microlensing in a circumbinary system with two stars and one planet.
While circumbinary systems are likely extremely common, few such systems have been discovered due in part to the increased observational difficulty. For instance, employing microlensing with a circumbinary system results in a three-lens problem with additional parameters and a 10-degree polynomial lens equation with no analytic solution.
“We explored all five parameters of the system: mass of the planet, distance of the planet, distance between the stars, angle of the system, and mass of the stars,” said author Eleni-Alexandra Kontou. “Each parameter affects the magnification map and light curves in a unique way.”
To analyze the effects of those parameters, the authors employed a combined analytical and computational method to generate exact magnification maps and light curves. Their results illustrate what to expect from observational data and demonstrate the advantages of the microlensing method.
“An important effect is seen in the distance of the planet: unlike what one might expect, the planetary caustic is as visible in the cases where the planet is far from the stars. It is only the shape that changes,” said Kontou. “That makes microlensing an ideal method to detect those far-away planets.”
Source: “An exploration of circumbinary systems using gravitational microlensing,” by Brett C. George, Eleni Alexandra Kontou, Patrycja Przewoznik, and Eleanor Turrell, American Journal of Physics (2022). The article can be accessed at https://doi.org/10.1119/5.0088604 .
