For decades, the supermassive black hole residing at the heart of the galaxy SDSS1335+0728 lay dormant. However, in 2019, this cosmic giant stirred, emitting a burst of light that astronomers captured in both visible and X-ray wavelengths. Located approximately 300 million light-years away,this galaxy is now experiencing what scientists are calling an awakening of its central black hole.The newly activated galactic nucleus has been dubbed “Ansky.”

the Revelation and Initial Observations

The initial detection of Ansky’s activity came from visible light observations. Following this, astronomers turned to X-ray telescopes to gather more data.

When Ansky began to shine in visible light images,we began tracking observations using NASA’s Swift X-ray space telescopes,and also checked archival data from the eROSITA X-ray telescope,but at the time we did not see any evidence of X-ray radiation.

Paula Sánchez Sáez, European Southern Observatory

Sánchez Sáez and her team were the first to investigate the black hole’s activity. Later, in 2024, another team detected X-ray bursts emanating from the same region.

This unusual phenomenon gives astronomers the chance to use X-ray space telescopes XMM-Newton and NASA’s NICER, Chandra and Swift to observe the behavior of black holes in real time.This phenomenon is known as quasi-periodic eruptions (QPEs), a QPE, a short-lived flashing event, and this is the first time they have observed such an event in a black hole that appears to be awake.

Lorena Hernández-García, University of Valparaiso in Chile

Possible Scenarios Behind Ansky’s Activity

The exact cause of Ansky’s sudden burst of activity remains a topic of inquiry.One common explanation for black hole activity involves the accretion of matter, often through a rotating accretion disk.

• Tidal Disruption Events (TDEs): These occur when a star passes too close to a black hole and is torn apart by its immense gravity, creating a disk of stellar debris.
• Accretion Disk Dynamics: Gas drawn into the black hole’s gravitational sphere can also form an accretion disk.

However, in Ansky’s case, there is no clear evidence of a star being destroyed.

The Mystery of the X-Ray Flares

The X-ray flares observed from ansky suggest a unique interaction within the accretion disk.One hypothesis involves an object passing through the disk without being wholly consumed.

The x-ray burst from Ansky is 10 times longer and 10 times brighter than what you would expect from a typical QPE.

Joheen Chakraborty, Massachusetts Institute of Technology

These energetic impacts could be responsible for the observed X-ray emissions.

Each of these eruptions releases 100 times more energy than we see elsewhere. The Ansky eruption also shows the longest cycle ever observed, at around 4.5 days. This pushes our model to its limits and challenges existing ideas about how these x-ray flashes are produced.

Future Research and Implications

Continued observation of Ansky and similar events is crucial for refining our understanding of supermassive black holes and their behavior. The team suggests continuous monitoring to better understand the repeated X-ray flares occurring approximately every 25 days.

These flares might be caused by an eccentric inner section of the accretion disk undergoing precession. Monitoring future QPEs will help test various models and potentially provide insights into gravitational waves.

We still have more models than data for QPE, and we need more observations to understand what’s going on.

Erwan Quintin, ESA X-ray Astronomer

Gravitational Wave Connection

The eruptions from Ansky may also be linked to gravitational waves, which could be detected by future missions like ESA’s LISA (Laser Interferometer Space Antenna).

QPE thought the result of small celestial bodies being captured by much larger celestial bodies and falling in a spiral towards them. The eruption of Ansky seems to tell us another story. These repeated bursts also mark the ESA’s future mission, LISA. [重力波検出器]may also be related to gravitational waves that might potentially be able to capture.These x-ray observations are extremely vital as they complement gravitational wave data and help solve the mysterious behavior of giant black holes.