London, June 19 (PTI): For the first time, astronomers have directly imaged the formation and expansion of a fast-moving jet of material ejected when a supermassive black hole ripped apart a star that wandered too close to the cosmic monster.
The scientists tracked the event with radio and infrared telescopes, including the National Science Foundation’s Very Long Baseline Array (VLBA), in a pair of colliding galaxies called Arp 299, nearly 150 million light-years from Earth.
At the core of one of the galaxies, a black hole 20 million times more massive than the Sun shredded a star more than twice the Sun’s mass, setting off a chain of events that revealed important details of the violent encounter.
Only a small number of such stellar deaths, called tidal disruption events, or TDEs, have been detected, although scientists have hypothesised that they may be a more common occurrence.
“Never before have we been able to directly observe the formation and evolution of a jet from one of these events,” said Miguel Perez-Torres, of the Astrophysical Institute of Andalusia in Spain.
“As time passed, the new object stayed bright at infrared and radio wavelengths, but not in visible light and X-rays,” said Seppo Mattila, of the University of Turku in Finland.
“The most likely explanation is that thick interstellar gas and dust near the galaxy’s centre absorbed the X-rays and visible light, then re-radiated it as infrared,” Mattila added.
Most galaxies have supermassive black holes, containing millions to billions of times the mass of the Sun, at their cores. In a black hole, the mass is so concentrated that its gravitational pull is so strong that not even light can escape.
“Because of the dust that absorbed any visible light, this particular tidal disruption event may be just the tip of the iceberg of what until now has been a hidden population,” Mattila said.
