Albert Einstein's theory of general relativity predicted the black hole's event horizon, the boundary in space-time beyond which events do not affect an outside observer.
The event horizon is referred to as the point of no return, where the gravitational pull becomes so great escape is impossible even for light.
While this assumption has been widely accepted, scientists want to prove that Einstein was right about his predictions. Now, researchers report proof of the existence of the event horizon.
In a new study, researchers conducted tests to find out if the event horizon really exists or not.
Using data from Pan-STARRS, the 1.8-meter telescope in Hawaii that has recently concluded a 3.5-year survey of half of the northern sky searching for things that change brightness, the researchers took a look at the center of galaxies.
What Lies At The Center Of Galaxies?
Supermassive black holes are believed to lie at the center of most galaxies, but there are some theorists who suggest the possibility that what lies in the heart of these galaxies may not be a black hole but a supermassive object that managed to avoid gravitational collapse.
The non-collapsed object would have a hard surface, which means that materials such as stars that are pulled closer and hit this hard surface would be destroyed. Stars that collide with a hard surface would produce a significant burst of light. Stars swallowed by black holes, on the other hand, would not create a transient signal, which glow for a while and then fade.
"We propose a novel observation that supports the existence of event horizons around supermassive BH candidates," the researchers wrote in their study published in the Monthly Notices of the Royal Astronomical Society.
"Instead of an event horizon, if the BH candidate has a hard surface, when a star falls on to the surface, the shocked baryonic gas will form a radiation pressure-supported envelope that shines at the Eddington luminosity for an extended period of time from months to years."
The researchers calculated that over a period of more than three years, they should see about 10 light flares if the objects at the center of the galaxies were solid instead of black holes, but they did not see any flare at all, supporting the idea that the objects at the center of galaxies are black holes that devour stars whole and not just compact, solid objects.
"Our motive is not so much to establish that there is a hard surface but to push the boundary of knowledge and find concrete evidence that really, there is an event horizon around black holes," said study researcher Pawan Kumar, from The University of Texas at Austin.
Study researcher Ramesh Narayan, from the Harvard-Smithsonian Center for Astrophysics, said that their findings imply that black holes have event horizons and that materials do vanish from observable universe once these are pulled into these exotic objects.
Event Horizon Telescope
The study may have provided a circumstantial evidence to support the idea of the black hole's event horizon, but scientist may soon be able to shed more light on this subject with the help of the Event Horizon Telescope's first images of a black hole.