[21 Dec 2021] The Physics Department of IPB University held an IPB Physics Talk #19, 16/12. In this 19th series, lecturers from the Theoretical Physics and High Energy Expertise Group, Department of Physics, Bandung Institute of Technology presented the topic “No Hair but Not Bald”.

At the beginning of his presentation, Prof Bobby Eka Gunara explained about black holes and the existence of black holes in the universe. He explained that black holes have infinite singularities.

“When light passes through the coordinates of the singularity (event horizon), the light will be absorbed due to the inverted nature of spacetime inside and outside the black hole,” said Prof Bobby.

Therefore, he said, a black hole can be described as a well that is infinitely deep. The existence of a black hole in the universe was detected in 2019 which has a mass of 6.5 billion times the mass of the sun. This black hole is in the center of M87 galaxy which was detected by several event horizon telescopes placed in several countries in the world.

He further explained, based on local characteristics, black holes are divided into two types, namely hairless and hairy black holes. Not only that, black holes have mass, mass density, electric charge, and angular momentum localized at a certain point consisting of static black holes (Schwarzschild and Reissner-Nordstrom black holes) and stationary (Kerr and Kerr-Newman black holes).

A stationary black hole rotates so that it has angular momentum and has both electric and magnetic field. On the other hand, hairy black holes occur at a certain distance in systems where gravity is coupled with scalar field or a Yang-Mills field.

This hairy black hole has ‘hairs’ originating from the scalar field and gauge field so that the density of this black hole still has mass at a certain distance from its center.

Professor Husin Alatas as the head of the Theoretical Physics Division, Physics Department of IPB University explained, the topic of black holes is a very interesting topic because there are still many things that have remained a mystery since it was first introduced. “This topic was presented three times in Physics Talk events throughout 2021 which explained different points of view,” explained Prof Husin Alatas. (*) (IAAS/PEH)