Complex sentence: In 2009, the first planet may have been discovered in the Andromeda Galaxy by using a technique called microlensing, which is caused by the deflection of light by a massive object.
Split into simpler sentences: In 2009, the first planet may have been discovered in the Andromeda Galaxy. This was detected using a technique called microlensing, which is caused by the deflection of light by a massive object.