Microlensing is a fascinating phenomenon where the light of a background star is deflected by the gravity of a foreground object towards an observer, temporarily magnifying the star as the foreground object crosses the observer's line of sight. We don't need to receive any light at all from the foreground object, and still we can use microlensing to measure its properties, like mass and distance. This makes it a great way to find objects that are too far away to be visible, like distant planets, brown dwarfs and neutron stars, and even those that are entirely invisible, like isolated black holes.
Microlensing events are transient and generally unpredicatable. Some events last for just 1 day while others can continue for months or even years, and they can result in very sudden and dramatic changes in brightness. All of this presents some serious challenges for observers trying to measure the properties of the event! LCO's ability to monitor astronomical objects at regular intervals for long periods, combined with its highly responsive scheduling system, makes it ideal to perform follow-up observations to characterize microlensing events.