Imagine you’ve just set up a settlement on an Earth-like world far beyond our solar system. After finishing your evening routine and dinner, you step outside to take in the view. Two stars are setting on the horizon, evoking a scene reminiscent of Star Wars. But there’s a striking difference—a massive planet dominates the sky above. As you already knew before arriving, you’re living on an exomoon that orbits a Saturn-sized planet, and together they circle two stars.
While such a scenario may still be centuries away, it hasn’t stopped an international team of scientists from making a remarkable discovery. They have identified a Saturn-sized exoplanet orbiting two M-dwarf stars—stars that are smaller and cooler than our Sun. The findings were recently published in the Publications of the Astronomical Society of the Pacific and were made using a less familiar detection technique called gravitational microlensing.
The team has labeled the discovery as microlensing event KMT-2016BLG-1337L, located about 7,000 parsecs (approximately 22,800 light-years) from Earth. By analyzing detailed light-curve models, the researchers were able to estimate the masses of the planet and its host stars, as well as the distances between them.
One model suggests the exoplanet has a mass of about 0.3 times that of Jupiter and orbits its host star at a distance of roughly 4 astronomical units (AU). A second model, however, estimates the planet to be much larger—around 7 Jupiter masses—with a closer orbit of about 1.5 AU. For comparison, Saturn itself has a mass of about 0.3 Jupiter masses. Despite the اختلاف in the planet’s size and orbit, both models agree on the properties of the binary star system: two M-dwarf stars with masses of approximately 0.54 and 0.40 times that of the Sun, separated by about 3.5 AU.
The study explains that “the event KMT-2016-BLG-1337L highlights the power of microlensing to detect planets in complex stellar environments, including systems that are beyond the reach of traditional detection methods.” This helps expand our inventory of planets in multi-star systems and improves our understanding of how planets form under such conditions.
As mentioned, microlensing is a relatively uncommon method for discovering exoplanets, accounting for just over 250 of the more than 6,100 confirmed so far. The technique works by using the gravity of a foreground star as a natural lens to magnify the light of a background star when a planet passes between them. Because a star’s gravity can bend the space around it, light from behind the star becomes amplified and visible from Earth. This is different from the more widely used transit method, which detects planets by observing dips in a star’s brightness as a planet crosses in front of it. In contrast, microlensing depends on the alignment of two stars and a planet passing between them to reveal its presence.
About the Author
