Israeli researchers have detected radio emissions from a distant galaxy that they say can radically change the understanding of how black holes behave.
When stars get close to black holes, they run the risk of breaking apart. If so, much of the material is expected to be consumed by the black hole, in a process that is supposed to take place in a few days and takes several weeks.
But physicists at the Hebrew University of Jerusalem and Tel Aviv University are raising the possibility of a still unexplained process that causes some black holes to go months or years before devouring the last remnants of a destroyed star.
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“There seems to be a physical process that we don’t yet understand that causes a long delay between the destruction of the star and the accumulation of material from the black hole,” Hebrew University physicist Assaf Horesh told The Times of Israel.
The peer-reviewed journal Nature Astronomy just published the research of Horesh, Tel-Aviv University’s Iair Arcavi, and NASA’s Swift Space Telescope Director Brad Cenko. After observing optical radiation from the destruction of a star in a galaxy 700 million light-years away in 2015, they began looking for radio emissions, hoping to detect them for a short period.
After the destruction of a star, physicists believe that it is common for some material to enter the black hole that caused its death. As part of this process, other materials are ejected by jets caused by magnetic fields around the black hole. Since it is thrown backwards at high speed, this is believed to create shock waves that generate radio emissions.
Scientists have experience detecting this immediately after the destruction of a star becomes observable on Earth, but Horesh and his colleagues ended up breaking new ground by detecting emissions over a four-year period.
“We saw optical radiation after the star was destroyed, and then there were no radio emissions for months,” said Horesh, lead author of the new research. “We decided to give him what we thought would be one last chance. Suddenly, six months later there was a radio broadcast, which vanished for a year.
“Then four years after the initial observation, we found that once again there was a very strong signal.”
He said the research suggests that the period during which a black hole consumes material from a star and spews out other material, generating radio emissions in the process, is longer “and somewhat more chaotic” than previously assumed. He added that his team is looking to expand their research by identifying more radio transmissions from various galaxies.