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Shop nowA shredded star revealed a wandering black hole
The full story behind my Short: TDE 2023mfm, an off-centre tidal disruption event.
The short version
A tidal disruption event (TDE) happens when a star passes too close to a massive black hole and is torn apart [1]. TDE 2023mfm, first found by the Zwicky Transient Facility on 28 June 2023, happened 1.08 kiloparsecs (about 3,500 light-years) from the centre of its host galaxy (projected distance) [1][2]. The black hole behind it is estimated at 106.2±0.5 solar masses (about 1.6 million Suns), with three methods giving roughly 1 to 10 million [1].
~3,500 lyprojected distance from the galaxy centre (1.08 kpc) [1][2]
~1.6 millionsolar masses (106.2±0.5, UV-plateau estimate) [1]
991 daysafter the optical peak, radio emission first detected [1]
Two black holes, one galaxy
The host is a massive galaxy (about 1011 solar masses) with a low-luminosity active nucleus. The team estimates the central black hole at about 108.3 solar masses, so the galaxy holds at least two massive black holes [1].
Late-time Hubble data suggest a stellar population of 107 to 108 solar masses at the TDE position, possibly a low-mass dwarf galaxy or a stripped galaxy from an earlier minor merger. A recent major merger looks unlikely; a minor merger is plausible [1].
Watch the Short
About this page
The Short uses real, illustrative photos from Wikimedia Commons (credited below); they are not photos of the study itself. This is an arXiv preprint and may change after peer review. Distances are projected (as seen on the sky).
Why it matters
- Finding hidden black holes. Wandering black holes are usually quiet; flares like this can reveal them [1].
- Delayed radio. Radio emission was not seen early, and was first detected about 991 days after peak, likely from a delayed outflow, though more observations are needed [1].
- A close cousin. It looks similar to another off-centre TDE, 2024tvd, in brightness and offset, but differs in radio and X-rays [1].
Full narration (transcript)
A star was torn apart, and it exposed a black hole nobody knew was there. The flare was first spotted by the Zwicky Transient Facility in June 2023. A tidal disruption event happens when a star gets too close to a massive black hole and is ripped apart. But this one wasn't at the centre of its galaxy. Hubble images put it about 3,500 light years from the galaxy's core. The black hole is estimated at about 1.6 million times the mass of the Sun. Meanwhile, the galaxy's centre has its own, much bigger black hole. So this galaxy holds at least two massive black holes. Hubble also spotted a faint clump of stars around the wanderer. It could be what's left of a smaller galaxy that merged in and was stripped. Radio waves from the event only showed up about 991 days after its peak. The findings, from a team led at UC Berkeley, are posted as a preprint on arXiv. Flares like this could help astronomers find more wandering black holes.
Sources
- [1] Sfaradi, I. et al. (2026). “An Off-Nuclear Tidal Disruption Event Discovered At Late Times: The Case Of TDE 2023mfm.” arXiv:2609.35998 (preprint). arxiv.org
- [2] Amazouz, L. (16 Oct 2026). “A Dying Star Just Revealed a Massive Black Hole That Astronomers Never Knew Was There.” dailygalaxy.com
Credits
Photos (illustrative, Wikimedia Commons): M87 jet (NASA and The Hubble Heritage Team (STScI/AURA), Public domain); P48 1994 Jean Large (Scan by Michael Vergara, CC BY-SA 3.0); The Sun by the Atmospheric Imaging Assembly of NASA's Solar (NASA/SDO (AIA), Public domain); Hubble2005-01-barred-spiral-galaxy-NGC1300 (NASA, ESA, and The Hubble Heritage Team (STScI/AURA), Public domain); HST-2009-01a (NASA (crew of STS-125), Public domain); Sun - SDO - 2014-06-10 304 (NASA/SDO, Public domain); M104 ngc4594 sombrero galaxy hi-res (NASA/ESA and The Hubble Heritage Team (STScI/AURA), Public domain); Firestorm of Star Birth in Galaxy Centaurus A (NASA, Public domain); Hubble image of globular cluster M13 (opo0840a) (NASA, ESA, and the Hubble Heritage Team (STScI/AURA), Public domain); Antennae galaxies xl (NASA, ESA, and the Hubble Heritage Team, Public domain); VLA Antennas (The Modern Polymath, CC BY-SA 4.0); The UC Berkeley Campanile tower. (15850494923) (Lorenzo Tlacaelel, CC BY 2.0); 036 Milky Way during Perseids seen from Oeschinensee with wa (Giles Laurent, CC BY-SA 4.0).