In a chance discovery by NASA’s Hubble Space Telescope, an unprecedented phenomenon has been observed: a supermassive black hole moving at incredible speeds and leaving behind a trail of newborn stars. This colossal event stretches over 200,000 light-years, twice the diameter of our Milky Way galaxy, and has likely resulted from a rare, chaotic dance among three massive black holes.
The speeding black hole, weighing as much as 20 million Suns, isn’t devouring stars like a cosmic Pac-Man. Instead, it’s plowing into gas in front of it, triggering new star formation along a narrow corridor. According to Pieter van Dokkum of Yale University, this is the first time astronomers have witnessed star formation trailing a black hole. The trail’s brightness is almost half that of the host galaxy it is linked to, suggesting a high number of new stars.
The extraordinary event is believed to be the result of multiple collisions of supermassive black holes. The first two galaxies likely merged around 50 million years ago, bringing together two supermassive black holes at their centers. A third galaxy, with its own supermassive black hole, then joined the fray, leading to an unstable configuration. One black hole robbed momentum from the other two and was ejected from the host galaxy, with the remaining binary black holes shooting off in the opposite direction.
To confirm the black hole explanation, follow-up observations with NASA’s James Webb Space Telescope and the Chandra X-ray Observatory are planned. The upcoming Nancy Grace Roman Space Telescope, with its wide-angle view and Hubble’s resolution, might also find more of these rare “star streaks” in the universe. According to van Dokkum, machine learning algorithms adept at finding specific peculiar shapes among astronomical data could be utilized for this purpose.
Pieter van Dokkum, Imad Pasha, Maria Luisa Buzzo, Stephanie LaMassa, Zili Shen, Michael A. Keim, Roberto Abraham, Charlie Conroy, Shany Danieli, Kaustav Mitra, Daisuke Nagai, Priyamvada Natarajan, Aaron J. Romanowsky, Grant Tremblay, C. Megan Urry, Frank C. van den Bosch. A Candidate Runaway Supermassive Black Hole Identified by Shocks and Star Formation in its Wake. The Astrophysical Journal Letters, 2023; 946 (2): L50 DOI: 10.3847/2041-8213/acba86