In October 2018, a small star shattered into fragments when it came very close to a black hole in the Galaxy, located 665 million light-years from Earth. This phenomenon came as no surprise to astronomers, as they often see such events when scanning the night sky. But even three years after this event, that black hole is again lighting up the sky. Scientists say that this black hole did not swallow anything.
Recent research suggests that the black hole is now ejecting material traveling at half the speed of light. But it is not known why it was delayed for so many years.
Astrophysical Yvette Cendes, author of the research published in the journal and Research Associate of the Center for Astrophysics, says that we are surprised. No one had seen anything like this before. He says that with the results of this research, scientists will be able to better understand the feeding behavior of black holes. Sandes compares this behavior to the burping that occurs after a meal.
The team noticed something unusual while reviewing the Tidal Disruption Incidents (TDEs) that have occurred over the years. Radio data from the Very Large Array (VLA) in New Mexico revealed that in June 2021, the black hole had mysteriously resurfaced. Sandes and his team investigated the incident closely.
The team examined TDE-AT2018hyz in multiple wavelengths of light, using VLA, Chile’s LMA Observatory, South Africa’s MeerKAT, Australia’s Australian Telescope Compact Array, Chandra X-ray Observatory and the Neil Gehrels Swift Observatory in space, and the data collected.
Edo Berger, professor of astronomy at Harvard University and co-author of the study, says that we have been studying TDE with radio telescopes for more than a decade. We sometimes think that they glow in radio waves, because the black hole first swallows them and then spews them out. But in the AT2018hyz the radio waves were silent for the first three years, and now it has become the highest radio luminous TDE ever seen.
Sebastian Gomez, a postdoctoral fellow at the Space Telescope Science Institute and co-author of the paper, says that when he first studied AT2018hyz in 2018 with the Visible Light Telescope, it was very unique. Gomez used theoretical models to calculate that the star that had been torn apart by the black hole was only one-tenth the mass of our Sun.
Astronomer here! My paper on this mysterious object has been published! TL;DR- we discovered a black hole that began an outflow of material TWO YEARS AFTER it shredded a star, and we don’t know why!https://t.co/FZIX0FJKJc
— Yvette Cendes (@whereisyvette) October 12, 2022
TDEs are known to emit light. As soon as a star comes near the black hole, the force of gravity starts spreading the star. Eventually, the material around the black hole heats up as it expands. This creates a flash that astronomers can see from millions of light years away.
Some spaghettified material sometimes goes back into space. Astronomers compare it to black holes, which are said to be able to swallow anything. But emissions, known as outflows, usually develop immediately after TDE. Sandes says that it seems as if this black hole has suddenly spewed out some material from the star eaten years ago.
The outflow of material is traveling 50 percent faster than the speed of light. Most TDE outflows travel 10 percent faster than the speed of light. Berger says that this is the first time that we have seen such a delay between swallowing and expelling. The next step is to find out if this really happens regularly.