What constitutes a “typical” exoplanetary system? It’s increasingly apparent that such systems differ significantly from our own Solar System. Notably, many exoplanets discovered do not have analogs among the planets we know, including entire categories of planets such as Hot Jupiters and Mini-Neptunes. Current detection methods are predominantly designed to find planets in proximity to their host stars, leaving a gap in our understanding of possible planets that reside in more distant orbits.
A new study, published on Thursday, explores so-called “microlensing” events, where the gravitational field of a planet magnifies the light of its parent star, resulting in a temporary increase in brightness. These instances are challenging to observe but could provide evidence for planets located far from their stars. The findings suggest a notable number of rocky super-Earths may exist within orbits similar to those of Jupiter and Saturn.
Lenses on the microscale
The two main techniques currently used to detect exoplanets are transit and radial velocity methods. The transit approach involves monitoring a star for slight decreases in its brightness, which can signify a planet passing in front and partially obscuring it. The radial velocity method detects changes in the star’s light spectrum, either red or blue shifts, which occur when a planet’s gravitational pull causes the star to wobble slightly as it orbits.
The gravitational effect of a planet is most pronounced when it is near its host star. Stars can also dim for various reasons unrelated to planetary presence, which leads researchers to typically require multiple transit observations for confirmation. This creates a bias towards finding planets with shorter orbital periods, which are typically located closer to their stars. Consequently, our understanding of exosolar systems is dominated by planets situated much nearer to their stars compared to the distance between Earth and the Sun. Remarkably, even the farthest exoplanets identified by the Kepler mission are located at distances comparable to that of Mars.
