It’s important to understand the context of the phrase “in most cases” and “eventually.” When mergers of large galaxies do occur, the process is gradual and can extend over millions or even billions of years. A single large galaxy might host up to 100 exceptionally large black holes, with approximately 10 of those exceeding 106 solar masses. The galaxy that contains the object designated AT2024tvd is notably large.
A significant implication of the multitude of black holes drifting through these galaxies is that not all will ultimately merge. If two black holes approach the central one simultaneously, gravitational interactions may propel the smaller black hole away at nearly the speed required to escape the galaxy’s gravitational influence. Consequently, these supermassive black holes can find themselves positioned far from the galaxy’s center for millions of years.
Currently, it remains unclear which scenario explains the location of AT2024tvd. While the galaxy in question does not appear to have experienced a recent merger, it is conceivable that the black hole is a remnant from an earlier merger event.
Interestingly, all galaxies that have exhibited an off-center tidal disruption event are sizable. The research detailing AT2024tvd suggests this correlation is not coincidental. Larger galaxies typically undergo more mergers throughout their histories, resulting in a higher number of supermassive black holes navigating their interiors. The study posits that only off-center events will be observable in substantial galaxies. This is due to larger galaxies housing bigger supermassive black holes at their centers. Once a supermassive black hole reaches a significant mass, its event horizon extends far enough that stars can traverse it without disruption, causing any energetic phenomena to occur within the black hole itself.
If one were situated close enough to witness this phenomenon, it is likely the star would simply vanish from sight.
The arXiv. Abstract number: 2502.17661 (About the arXiv). This work is set to be published in The Astrophysical Journal Letters.
