Black Holes have been romanticized over the centuries as enigmatic cosmological entities through which no light can escape. But what if I were to tell you that there is a way (at least in theory) that you could see what is inside a black hole. How? The answer is simple – a naked singularity.
While a black hole comprises of a gravitational singularity (a point of infinite density where the laws of normal spacetime do not work) and an event horizon, a naked singularity does not comprise of an event horizon. What does this mean? Unlike the space-time in a black hole that cannot be viewed by an outside observer, the space-time in a naked singularity can be viewed by an outside observer. Thus, naked singularities open an opportunity for an outside observer to see the space-time evolve around the gravitational singularity in a naked singularity. This could open a new realm of discovery for us, because it will allow us to study the behavior of gravity around a gravitational singularity.
Thus, a naked singularity would not just be an abrupt ‘hole’ that distorts the space-time curvature, it would annihilate the laws of physics along its path. As a matter of fact, the cosmic censorship hypothesis was suggested to preserve the laws of physics predicted by General Theory of Relativity in our universe. The cosmic censorship hypothesis argues that gravitational singularity will always remain concealed by the event horizon, and because black holes follow the cosmic censorship hypothesis, it means that the general theory of relativity and laws of physics can continue to work around a black hole. However, if a naked singularity is detected in our universe, it means that our laws of physics and the General Theory of Relativity are at threat
Scientists have not yet seen a naked singularity, but its existence has been debated upon with new mathematical proofs. One of the arguments to prove the existence of naked singularities is to assume that Loop Quantum Gravity (LQG) is correct. LQG is a theory that blends Quantum Mechanics and General Relativity to explain the quantum effects in gravity. Apart from LQG a few other mathematical simulations and models hint that naked singularities do exist.
In 2017, UK physicists Toby Crisford and Jorge Santos from the University of Cambridge simulated a naked singularity in a three-dimensional universe like ours. However, the universe in the simulation, had a different shape than ours. While our universe is assumed to be flat, the three-dimensional universe simulated by Toby Crisford and Jorge Santos was a saddle-shaped universe called the Anti-de Sitter space. This shape is particularly famous for its point of no return, where light is reflected back onto itself.
Though not seen, researchers like Dr. Ramesh Narayan and Dr. Pankaj S. Joshi believe that a naked singularity can exist in our own universe. They have used other approaches to prove the theoretical existence of a naked singularity in our own universe. For instance, if matter were to condense very gradually instead of a supernova, theory does allow for the formation of a point-like naked singularity. There are ways that have been devised to allow for such a gradually collapsing process in case of a star.
Moreover, researchers have also begun exploring ways to observationally distinguish a naked singularity from a black hole by analysing the radiation emitted from the accretion disk around the two objects. In fact, Dr. Pankaj S. Joshi and Dr. Rajibul Shaikh’s paper on distinguishing naked singularities from black holes by their accretion disk has considered a study of images of ‘thin accretion disks around black holes and two classes of naked singularity spacetimes’ in order to compare the two scenarios. Their paper shows that black holes will tend to have single accretion disk with the inner edge lying outside the proton sphere, but a naked singularity can either have double disks or a single disk extending up to the singularity.
To conclude, though the existence of naked singularities in our Universe has not been proved, various research papers and research evidences suggest the existence of a naked singularity in our universe or one that is identical to ours. In my opinion, the weirdness of observing an actual gravitational singularity in a naked singularity will not only help scientists observe a region of infinite density, but we will also help them understand why our laws of physics break down near a singularity. We all know that stars collapse, but it is not truly known what comes after that and with naked singularity popping up as another option, all we can do is to keep digging deeper. So, while I attempt to comprehend “The story of collapsing stars” by Dr. Pankaj S. Joshi, trying to dig deeper on this topic, you can continue to speculate and innovate, till you constipate!