Ansky (black hole)

Ansky is the nickname for a supermassive black hole located in the galaxy SDSS J133519.91+072807.4 (SDSS1335+0728), approximately 300 million light-years from Earth in the Virgo constellation. The black hole gained attention in 2019 when it transitioned from dormancy to an active state, producing extreme quasi-periodic eruptions (QPEs) of X-ray radiation. It represents the first observed case of a supermassive black hole awakening in real time.

Discovery

The galaxy SDSS1335+0728 remained inactive for two decades before suddenly brightening in December 2019. The Zwicky Transient Facility (ZTF) detected this optical brightening and assigned the designation ZTF19acnskyy.[1] The nickname "Ansky" derives from the suffix "acnskyy" in this original identifier.[2][3]

The initial brightening was discovered through the ALeRCE (Automatic Learning for the Rapid Classification of Events) machine learning classification system.[4][1] For four years following the 2019 event, the galaxy exhibited optical variability without detectable X-ray emissions.[4]

The central black hole has an estimated mass of approximately 10^6 solar masses.[1] The host galaxy SDSS1335+0728 is classified as an early-type galaxy located at redshift z=0.024.[1] The galaxy is now classified as a galaxy with active galactic nucleus.[4]

Quasi-periodic eruptions

In February 2024, astronomers detected recurring X-ray flares from Ansky, marking the beginning of unprecedented quasi-periodic eruptions.[5] These eruptions exhibit several extreme characteristics: each eruption lasts approximately 1.5 days; QPEs repeat every 4.5 days, the longest interval observed for any QPE source. Each burst releases approximately 10^48 ergs, representing 100 times more energy than typical QPEs, ten times more luminous than standard QPEs. A longer 25-day cycle containing cascades of five consecutive eruptions was also found.[5] The eruptions involve the ejection of approximately one Jupiter mass of material at velocities reaching 15% of the speed of light.[3] Ansky is the first supermassive black hole observed transitioning from dormancy to activity. Observed QPEs are the most energetic and longest-duration QPEs on record. The source lacks evidence of recent stellar destruction, suggesting QPEs can occur through newly formed accretion flows rather than only after star disruption events.[5]

Observational campaigns

Multiple space-based telescopes have monitored Ansky since its activation:[5][3]

  • NASA's NICER space telescope conducted high-cadence monitoring from May to July 2024, observing the source approximately 16 times daily[3]
  • ESA's XMM-Newton provided three 30-kilosecond dedicated observations and detected the quiescent accretion disk between eruptions[5]
  • NASA's Swift Observatory contributed to initial follow-up observations[4]
  • NASA's Chandra X-ray Observatory was a part of the multi-instrument monitoring campaign[5]

These observations detected 165 QPE events during the initial monitoring period and captured 12 near-consecutive flares over a 60-day campaign.[5]

Theoretical models

Current theories propose that QPEs result from interactions between the black hole's accretion disk and orbiting objects. For Ansky, researchers suggest a larger debris disk around the black hole, which is "larger and can involve objects farther away" than usually theorised.[3]

Since activation, Ansky has shown systematic changes across the electromagnetic spectrum:[1][4]

  • Ultraviolet: Four times brighter than pre-2019 levels since 2021[1]
  • Mid-infrared: More than doubled in brightness since June 2022, with reddening of the W1-W2 color[1]
  • X-ray: Emissions began in February 2024, transitioning from undetectable to extreme QPE behavior[5]
  • Optical: Persistent variability since December 2019, with spectroscopic changes indicating enhanced ionization[1]

Further reading

  • Chakraborty, Joheen; Kosec, Peter; Kara, Erin; Miniutti, Giovanni; Arcodia, Riccardo; Behar, Ehud; Giustini, Margherita; Hernández-García, Lorena; Masterson, Megan; Quintin, Erwan; Ricci, Claudio; Sánchez-Sáez, Paula (9 May 2025). "Rapidly Varying Ionization Features in a Quasi-periodic Eruption: A Homologous Expansion Model for the Spectroscopic Evolution". The Astrophysical Journal. 984 (2): 124. arXiv:2504.07167. Bibcode:2025ApJ...984..124C. doi:10.3847/1538-4357/adb972.

References

  1. ^ a b c d e f g h Sánchez-Sáez, P.; et al. (August 2024). "SDSS1335+0728: The awakening of a ∼10 6 M ⊙ black hole". Astronomy & Astrophysics. 688: A157. doi:10.1051/0004-6361/202347957. ISSN 0004-6361.
  2. ^ Shavit, Joshua (April 15, 2025). "A sleeping black hole just woke up - erupting powerful x-ray bursts". The Brighter Side of News.
  3. ^ a b c d e "NASA's NICER Maps Debris From Recurring Cosmic Crashes - NASA Science". NASA. 6 May 2025. Retrieved 13 August 2025.
  4. ^ a b c d e "Astronomers see a massive black hole awaken in real time". www.eso.org. Retrieved 13 August 2025.
  5. ^ a b c d e f g h Hernández-García, Lorena; et al. (June 2025). "Discovery of extreme quasi-periodic eruptions in a newly accreting massive black hole". Nature Astronomy. 9 (6): 895–906. arXiv:2504.07169. Bibcode:2025NatAs...9..895H. doi:10.1038/s41550-025-02523-9. ISSN 2397-3366.
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