Bizarre ‘gravitational molecules’ can orbit black holes

Only three things define a black hole: its total mass, its electrical charge and its angular momentum (or spin, a physical quantity associated with its rotation). According to a group of researchers from the Gravitation on Técnico (GRIT) group at the Instituto Superior Técnico, this simplicity is repeated in the electrons of an atom; just as these particles orbit the atomic nucleus, particles that are still unknown may be spinning around singularities.

To understand how physicists Taishi Ikeda, Laura Bernard, Vitor Cardoso and Miguel Zilhao came to this conclusion, it is necessary to understand a fundamental concept of physics: the field.

There are fields such as scalar, vector and tensor. What the researchers used was the scalar – in a simple definition, it is the one in which all the points present quantities without direction and sense. Good examples are temperature maps of a region or population densities of a city: the number is the same.

From macro to micro

The notion of field is already known old mathematics; only in the last century, it began to be used also by physics to explain the Universe, implying that the cosmos (and everything in it) is, in reality, a scalar field. And so we get to the electron.

In 1926, scientist Werner Heisenberg stated that it is not possible to determine, at the same time and with precision, the speed and position of an electron – by increasing the precision in determining one, the accuracy in determining the other is lost. This is where Heisenberg’s uncertainty principle emerged, which became less uncertain when it was stipulated that, instead of considering a definite orbit for the electron, it would be better to admit that there are possible regions for this electron to be – or a field.

Both electrons and black holes are defined by their mass, their spin and their electric charge. Electrons are tiny particles that orbit one or more nuclei (as in the hydrogen molecule, or H2). If there are fields around the nucleus of an atom orbiting electrons, a singularity (or even two) surrounded by a field would also be possible.

This is what the study authors found: scalar fields can exist around binary black holes, or even organize themselves in the way that electron fields in molecules.

Gravitational molecules

It gets a little complicated now, because two of the most mysterious things in the science of the cosmos come into play today: dark matter and dark energy – just as electrons exist in scalar electron fields, they too can be composed of one or more scalar fields.

Let’s imagine that dark matter is, in fact, distributed in a field, existing as dark particles orbiting around binary black holes, in very specific trajectories in the same way that electrons behave inside atoms.

Binary systems of binary black holes do not last: with their monstrous gravitational force, they end up colliding with each other and forming a single singularity and propagating, with shock, gravitational waves.

What the GRIT researchers believe is that the fields around the two black holes would affect these emitted gravitational waves, filtering, deflecting and giving new shapes to the waves that pass through where the dark matter would be.

The mark of these “gravitational molecules” could be picked up by interferometers on Earth – that is, astrophysicists would be able to detect this type of matter and thus, perhaps discover that black holes, after all, are not as simple as they seem.

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