Unveiling the Cosmic Awakening: When Black Holes Stir

Astronomy enthusiasts were recently captivated by the sudden burst of activity in the tranquil galaxy SDSS1335+0728. Observations revealed an extraordinary display of ultraviolet, visible light, infrared, and X-ray emissions, indicating a cosmic spectacle unfolding within. Scientists attribute this phenomenon to the awakening of a massive black hole at the galaxy’s core, igniting what is known as an active galactic nucleus.

The remarkable surge in brightness is believed to stem from the voracious appetite of the central supermassive black hole, rapidly devouring surrounding gases. This celestial event offers valuable insights into the mechanisms driving black hole growth and evolution, shedding light on the enigmatic processes occurring at the heart of galaxies.

The observations hint at the formation of an active galactic nucleus, a pivotal moment in astronomical studies. While further research is needed to confirm this phenomenon, the discovery paves the way for a deeper understanding of how active galactic nuclei awaken and evolve over time.

In the vast expanse of the cosmos, the awakening of SDSS1335+0728 serves as a reminder of the dynamic and ever-changing nature of our universe, inviting us to marvel at the cosmic wonders unfolding before our eyes.

 Suddenly brighten

In December 2019, astronomers were surprised to discover that 300 million light-years away, a quiet galaxy named SDSS1335+0728 suddenly became active, emitting ultraviolet, visible and infrared light into space. Even more surprising, in February of this year, astronomers discovered that the galaxy was becoming more and more active – it began to emit X-rays.

What causes a quiet, ordinary galaxy like the Milky Way to suddenly show huge changes in brightness? To understand why, astronomers used observational data from multiple space-based and ground-based observatories.

In a study published recently in the journal Astronomy & Astrophysics, astronomers believe they may be witnessing a supermassive black hole beginning to devour surrounding gas, transforming itself into an active galactic nucleus (AGN). This is a change that has never been observed in galaxies.

  Awakening Black Hole

Initially, the unusual brightness changes of SDSS 1335+0728 were detected by the Zwicky Transient Source Facility (ZTF). The ZTF is an automated telescope used to look for changing objects in the night sky. At first, researchers thought that this should be a regular AGN event.

About 10% of galaxies have a bright active galactic nucleus at their center. Astronomers believe that active galactic nuclei form when a disk of gas forms around the black hole at the center of a galaxy and gas begins to be sucked in. At such extreme gravity, friction on the disk can heat the gas to very high temperatures, producing intense radiation.

Some past studies have shown that AGNs appear to change in brightness over time, pulsing intermittently over very long time scales (10,000 to 10 million years). But in this case, when the researchers looked back at archival data over the past 20 years, they found no clear signs of activity from SDSS1335+0728.

This piqued the curiosity of astronomers. They decided to use archival images and spectra from six different telescopes to trace the galaxy’s quiet past. Then, they used the Southern Astrophysical Research Telescope (SOAR), Glenelg Swift Observatory (Swift), Keck Observatory (WMKO) and the Very Large Telescope (VLT) to conduct tracking observations. These observatories cover everything from X-rays to ultraviolet to A large amount of key data is collected in the optical and infrared light bands.

After comparing observational data before and after December 2019, the researchers found that SDSS1335 +0728 now radiates more light in the ultraviolet, optical and infrared bands. And in February 2024, it will start emitting X-rays. This phenomenon is unprecedented.

Through further observations and analysis, the research team concluded that the possibility that best explains this rapid brightening is that at the center of SDSS 1335 0728, there is a black hole with a mass 1 million times that of the sun. This supermassive black hole is “awakening” and starting an active galactic nucleus. If this possibility is ultimately confirmed, it would mark the first time that astronomers have observed the “black hole awakening” process in real time and captured the start-up of an active galactic nucleus.

However, there are some phenomena that can also explain the sudden glow of galaxies, such as tidal disruption events. A tidal disruption event occurs when a star gets too close to a black hole and is torn apart. However, such events typically result in much brighter signals, and they typically only last for tens, or at best, hundreds of days.

  Awaiting further testing

Researchers said that all the observed data so far indicate that astronomers may have observed the formation of active galactic nuclei for the first time. However, this does not rule out the possibility that this is the result of an unusually slow tidal disruption event, or even an unknown new phenomenon.

They hope that future observations with the VLT and the soon-to-be-commissioned Extremely Large Telescope (ELT) will further rule out other explanations and learn more about the mechanisms leading to the awakening of active galactic nuclei. Regardless of what exactly causes this change in brightness, these studies provide valuable information about how black holes grow and evolve, and could help reveal whether our galaxy might one day stage a similar event.

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