Star Disappears in Andromeda Galaxy, Possibly Becoming a Black Hole
A bright star in the Andromeda galaxy, a galactic neighbor to our own Milky Way, has seemingly disappeared, leading astronomers to believe it may have collapsed into a black hole. The star, previously visible with modest telescopes, is now barely detectable even with the James Webb Space Telescope.
Kishalay De, an astronomer with Columbia University and the Flatiron Institute, and his colleagues documented the star’s vanishing act whereas analyzing archival data collected over 15 years by NASA’s NEOWISE spacecraft. Their research, published in the journal Science, initially aimed to map changes in stellar brightness in infrared light. The team tracked millions of stars over time, and one stood out as an anomaly.
Around 2015, the star experienced a sudden brightening lasting approximately one year. Following this, it began to fade rapidly, both in infrared and visible light. By a few years later, it was no longer visible in optical wavelengths. “It used to be one of the brightest stars in the Andromeda galaxy,” De said. “Today, We see nowhere to be seen, even with the most sensitive telescopes.”
The Andromeda galaxy, similarly known as Messier 31 (M31), is located roughly 2.5 million light-years from Earth and is the closest spiral galaxy to the Milky Way, according to NASA. Astronomers utilize observations of Andromeda to better understand the structure and evolution of our own galaxy, a task complicated by Earth’s position within the Milky Way.
Scientists have long theorized that massive stars can die by collapsing directly into black holes, a process that would be relatively quiet compared to the explosive death of a supernova. The observed fading pattern aligns with this theory, suggesting the remaining glow in infrared light is powered by stellar material continuing to fall into the newly formed black hole. “We would predict that this continues to fade away into darkness,” De stated, adding that this process could take decades to fully observe.
Suvi Gezari, an astronomer at the University of Maryland who was not involved in the research, highlighted the significance of using long-term infrared observations to reveal this obscured process. “It’s a really clever use of infrared light observations over a long time period to open up this process that is otherwise obscured by dust and very faint and difficult to observe,” she said.
This isn’t the first instance of a disappearing star. Astronomers have identified one other similar case, though that star was farther away and fainter, resulting in less detailed observations. Christopher Kochanek, an astronomer with Ohio State University who has studied the previous event, described the current findings as “pretty similar.”
Kochanek emphasized that this approach—long-term infrared monitoring—is currently the most effective method for detecting black hole formation. However, he cautioned that alternative explanations exist, such as the possibility of merging stars obscured by dust. “Fundamentally, the only way to clearly answer this either way is that death is forever. It needs to fade to black,” he said.