Star on a Death Spiral: How a Doomed Celestial Body Nearing a Supermassive Black Hole is Set to Be Torn Apart in Under 6 Years

A distant star is facing an exciting yet terrifying fate. It’s caught in a death spiral, repeatedly diving into a hot gas disk around a black hole, releasing powerful X-ray bursts as it goes. This star is part of a galaxy called LEDA 3091738, located about 300 million light-years away. The black hole, affectionately named “Ansky,” has a smaller companion that orbits closely.

The name “Ansky” comes from its official designation, ZTF10acnsky, marked by its explosive activity, first noticed by the Zwicky Transient Facility at California’s Palomar Observatory in 2019.

New research shows that Ansky erupts in X-rays roughly every four and a half days. Each explosion lasts about a day and a half before fading away. Astronomers refer to these phenomena as “quasi-periodic eruptions,” or QPEs. Ansky is particularly noteworthy because it produces the most energetic QPEs discovered so far, with just eight such sources known in the entire universe.

Joheem Chakraborty, a Ph.D. student from the Massachusetts Institute of Technology, led a recent study using the Neutron star Interior Composition Explorer (NICER) on the International Space Station alongside the European Space Agency’s XMM-Newton space telescope. In Chakraborty’s words, “QPEs are mysterious and intensely interesting. We’re working to understand the causes behind them, and Ansky’s unique behavior is helping us develop better tools.”

The black hole at the heart of this system has a mass roughly equivalent to a million suns. It’s surrounded by an accretion disk—a swirling mass of hot gas waiting to be consumed. The companion star, likely lower in mass, orbits close enough to disturb this disk. These disturbances create shockwaves, heating the gas, and expelling it into space, resulting in the observed X-ray bursts.

According to Lorena Hernández-García from the Millennium Nucleus on Transversal Research and Technology to Explore Supermassive Black Holes, Ansky features a larger disk than typical QPE systems. This allows materials to be involved from farther away and results in longer eruption times.

Chakraborty’s team monitored Ansky intensively—16 times daily between May and July 2024—to track changes in the eruption frequency. Each outburst expels gases equivalent to Jupiter’s mass at speeds approaching 15% of light speed. This process gradually steals energy from the star, causing it to spiral closer to the black hole.

If the star shares a mass with our Sun, it could take around 400 eruptions, or roughly 5 to 6 years, for it to completely lose its orbital energy. This situation could lead to even more frequent QPEs until the star is either torn apart by gravitational forces or merges with the black hole. If the star is heavier than the Sun, it may last a bit longer.

Chakraborty notes, “We’re going to keep observing Ansky. There’s so much to learn.” Continuous monitoring will help astronomers predict when the star will reach its end, allowing them to witness a spectacular display of destruction in real-time.

Recent studies underscore the importance of observing phenomena like QPEs. As we learn more, we may unravel the secrets of black holes and their impact on surrounding celestial bodies. The recent findings from Ansky were published in The Astrophysical Journal.

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