Invisible, intangible and undetectable save for the glowing accretion discs that give them an eerie halo, black holes are one of the mysteries of the universe that keep opening portals to even more mysteries. Science has assumed these astral corpses are a sort of gravitational vortex—but how can we be sure they actually are holes and not heavy dark masses suspended in space?
Backed by Einstein’s theory of general relativity, scientists believe black holes are extremely dense micro-masses at the core of an area from which any light or energy that enters can never escape, aka the event horizon. It’s like a cosmic version of the “Point of No Return” scene in The Phantom of the Opera. The question that continues to haunt us is whether they aren’t just enormous massive spheres that elude our eyes.
To prove these dead stars really have collapsed in on themselves from the force of their own gravity, a team of scientists recently investigated the phenomenon. Stars are shredded by the intense gravity in what is better known as a tidal disruption event. If black holes really were uniform dark spheres that had at least the same radius as their event horizons, the team argues, then they would have stars smashing into them at the speed of light and (as they were being mercilessly destroyed) giving off unmistakable emissions we could actually see. The study found no evidence of these emissions.
“We calculated the outcome of such collisions, which would be visible at cosmological distances billions of light-years away,” said Wenbin Lu, an astrophysics grad student at the University of Texas, whose team recently published their findings in the Monthly Notices of the Royal Astronomical Society.
Uncertainty still hovers over the study. Even theory that proves itself over and over on paper cannot call itself fact. The team’s calculations really only worked for supermassive black holes, which are tens of millions of times more massive than even the sun. Black holes were also theoretically limited in size to be just slightly larger than the radii of their event horizons. The question of how fast they spin was never factored in. There is also the issue of whether they really are dark orbs and, because of gravitational redshift, the emissions from epic star collisions are just too faint to observe at this distance.
Black holes will remain beyond the realm of sight for now, which will inevitably spawn more theories and possibly a séance to discuss them with the ghost of Einstein, but scientists are optimistic that the Event Horizon Telescope will (literally) see their secrets in the future.