Astronomers Investigate Mysterious "Phoebe" Object After Brief Gravitational Lensing Event

On December 18, 2019, a star located in the Large Magellanic Cloud experienced a sudden, brief surge in brightness that lasted only one hour. This transient event caught the attention of researchers at Swinburne University, who determined that the star’s light had been warped by a massive, unseen object passing directly between the star and Earth. This phenomenon, known as gravitational microlensing, occurs when the gravity of a foreground object acts as a lens to focus and magnify light from a more distant source.

The mysterious object responsible for this fleeting display has been dubbed "Phoebe." Unlike typical gravitational lensing events that involve static, long-term alignments, Phoebe’s rapid transit suggests a high-velocity body moving through space. Because the lensing effect was so short-lived, identifying the nature of this object has become a primary objective for the research team. Understanding what Phoebe actually is could provide significant insights into the composition of the galaxy and the distribution of mass in deep space.

In a recent study, astronomers proposed three distinct theories to explain the identity of Phoebe. The first two possibilities suggest that the object is a rogue planet—a world ejected from its host star system—either originating from within the Milky Way or from the Large Magellanic Cloud itself. If the latter is confirmed, it would represent the first discovery of an extragalactic rogue planet. A third, more exotic hypothesis posits that Phoebe could be a primordial black hole, a dense relic dating back to the earliest moments following the Big Bang. Researchers continue to analyze the data to determine which of these fascinating candidates is responsible for the 2019 event.