Black holes are known for their insatiable appetite, devouring anything that gets too close to them. However, a recent discovery reveals a new phenomenon dubbed “partial or repeating tidal disruption” where a black hole engages in a “snacking” behavior on a star. Instead of completely destroying the star in one event, the black hole slowly wears it down through repeated encounters.
This process was observed on a star called Swift J023017.0+283603 (or Swift J0230 for short) by NASA’s Neil Gehrels Swift Observatory. Located over 500 million light-years away in a galaxy known as 2MASX J02301709+2836050, Swift J0230 was captured by the Pan-STARRS telescope in Hawaii.
During each encounter, the gravitational forces cause the star to bulge outward, leading to material being stripped away and consumed by the black hole. While an individual encounter is not enough to destroy the star, it continues until the star’s orbit brings it close to the black hole again, resulting in further material loss.
In the case of Swift J0230, the star loses approximately three Earth masses of material with each encounter. This process of mass loss continues until the star runs out of material and eventually breaks apart.
The discovery of this phenomenon was made possible through a new method of data analysis applied to observations from the Swift Observatory. Originally designed to study gamma-ray bursts, the observatory’s X-ray Telescope instrument was repurposed to regularly observe different parts of the sky. By comparing the data to previous observations, any changes are identified, signaling a transient event. Objects of interest, such as Swift J0230, are then investigated by the research team.
The Swift team member Phil Evans of the University of Leicester emphasized the adaptability and versatility of the observatory’s hardware, software, and the skills of its international team. This new capability expands the range of astrophysics research conducted by the Swift Observatory, continuing the legacy of its namesake, Neil Gehrels, who oversaw and supported various transitions during the mission’s lifetime.