Dr Chakraborty draws upon an analogy between gravitational force and electromagnetism to say that mass is like electric charge and can exist independently, thus it can be called a “gravito-electric charge”.
Break a magnet and you will get a smaller magnet having two poles. While positive and negative electric charges can be found to exist independently, the poles of a magnet are always found in pairs, north and south bound together. But there is an asymmetry between electricity and magnetism. In the nineteenth century, James Clerk Maxwell unified electricity and magnetism as one combined phenomenon, showing that light is an electromagnetic wave. In all, that leaves four possibilities in principle. In the above paper, Chandrachur Chakraborty, from the Department of Physics, Indian Institute of Science, Bengaluru, and Kavli Institute of Astronomy and Astrophysics, Peking University, Beijing, China, and his collaborators show that M87* could be either a black hole or a naked singularity and each of these possibilities could be plain or coupled with what is called a gravitomagnetic monopole. Joshi is the Founding Director of International Center for Cosmology and Advisor, Charusat University, Anand, in Gujarat, and is not involved in the work under discussion.
While many physicists object because of some seriously problematic issues associated with the solutions, these nevertheless exist, puzzling researchers, perhaps embarrassing them. If this weird object should exist, observers can, in principle, see the bare, or “naked” singularity as it is called. Joshi, a specialist in general theory of relativity and cosmology, calls this “naked singularity” a “troublesome sibling” of a black hole in an article by him in Scientific American. In many scenarios of stellar collapse, the event horizon does not form, and the singularity is exposed to the outside, without any event horizon shielding it. Hence, all the physics happening within the black hole’s event horizon is indeed blocked from the view of the observer. That is why, we cannot see the singularity at the heart of a black hole but only see points outside the event horizon. Not even light can escape the pull of the singularity once it crosses the event horizon. Then there is the event horizon – an imaginary surface surrounding the singularity, and the gravity of the object is such that once anything enters this surface, it is trapped forever. A black hole has two parts: At its core is a singularity – a point that is infinitely dense, as all the remnant mass of the star is compressed into this point. When stars much more massive than the Sun reach the end of their lives, they collapse under their own gravity, and the product of this collapse, most astronomers believe is a black hole. The authors say it (M87*) is not necessarily a black hole but could even be a “naked singularity with a gravitomagnetic monopole.” The European Physical Journal C brings in an alternative explanation for the compact object that was imaged by the Event Horizon Telescope. The discovery set the world of astronomy on fire and also found a mention in the “popular information” section of the announcement of the Nobel Prize in physics for 2020, when Andrea Ghez and Rheinhard Genzel were awarded half the share of the prize for their study of the black hole at the centre of the Milky Way galaxy, Sagittarius A*. This black hole is calculated to be 6.5 billion times the Sun’s mass and is 55 million light years away from the Earth. In 2019, astronomers of the Event Horizon Telescope captured the first ever image of a supermassive black hole (M87*) which was located at the centre of a galaxy Messier 87 (M87).