Figure 1: Artist’s impression of a gas giant planet.
OGLE-2011-BLG-0265Lb is a Jupiter-mass gas giant planet in orbit around a red dwarf star. It was detected using a technique known as gravitational microlensing. When a foreground star crosses the line of sight to a background star, the gravitational field of the foreground star can act as a lens and magnify the brightness of the background star. This phenomenon can be observed as a light curve where the brightness of the background star changes with time. If the foreground star has a planet around it, the presence of the planet can induce perturbations in the light curve.
The gravitational microlensing light curve indicating the presence of OGLE-2011-BLG-0265Lb yields two solutions. For the first solution, the planet has 1.0 ± 0.3 times the mass of Jupiter and it orbits a star with 0.23 ± 0.07 times the mass of the Sun. For the second solution, the planet has 0.6 ± 0.2 times the mass of Jupiter and it orbits a star with 0.15 ± 0.06 times the mass of the Sun. In both cases, the planet is ~2 AU from its host star - a red dwarf star. At that distance, the planet is well beyond the "snow line" of its host star and it can be considered a "cold Jupiter".
The discovery of OGLE-2011-BLG-0265Lb is an important one because gas giant planets are very rare around red dwarf stars. The core accretion mechanism of planet formation predicts that gas giant planets rarely form around red dwarf stars, while the disk instability mechanism of planet formation predicts that gas giant planets can form around red dwarf stars. Detecting more planets like OGLE-2011-BLG-0265Lb around red dwarf stars can provide more insight on the formation scenario of such planets.
Figure 2: Gravitational microlensing light curve indicating the presence of OGLE-2011-BLG-0265Lb. The planet’s perturbations to the light curve are marked with arrows. Skowron et al. (2014)
Skowron et al. (2014), "OGLE-2011-BLG-0265Lb: a Jovian Microlensing Planet Orbiting an M Dwarf", arXiv:1410.8252 [astro-ph.EP]