Both MOA-2007-BLG-197Lb and its host star are located at a distance of roughly 14,000 light years from Earth. MOA-2007-BLG-197Lb is a valuable find because there appears to be a lack of brown dwarfs around Sun-like stars. One reason could be because brown dwarfs orbiting Sun-like stars lose angular momentum due to tidal interactions with their host stars, causing the brown dwarfs to spiral in and fall into their host stars. Nonetheless, gravitational microlensing is a great technique for detecting free-floating brown dwarfs, brown dwarf binaries and brown dwarf companions to stars. Future detections of brown dwarfs around Sun-like stars will offer better insight on the population distribution of brown dwarfs.
Light curve of the gravitational microlensing event that led to the detection of MOA-2007-BLG-197Lb and the best-fit model (solid line). The insert on the right shows a zoom-in of the “spike” in the light curve generated by the presence of MOA-2007-BLG-197Lb. Ranc et al. (2015).
Ranc et al. (2015), “MOA-2007-BLG-197: Exploring the brown dwarf desert”, arXiv:1505.06037 [astro-ph.EP]