2024-03-07 12:00:09
Astronomers have just revealed an exceptional discovery: a pair of supermassive black holes, the heaviest ever observed, with a combined mass equivalent to that of 28 billion Suns.
These cosmic giants are found in a galaxy fossil (A fossil (derived from the noun of the Latin verb fodere: fossil, literally…) named B2 0402+379, and are located only 24 light years apart. Despite this extreme proximity, they are engaged in an endless orbital dance, without getting any closer, a cosmic ballet that has lasted for more than 3 billion years.
Credit: NOIRLab/NSF/AURA/J. daSilva/M. Zamani
Black holes arise from the collapse of gigantic stars and increase their mass by capturing everything that passes near them, whether gas, dust, stars or other black holes. However, how the first black holes appeared remains a mystery.
Simulations of the “cosmic sunrise”, that is to say the first billion years of the Universe, suggest that black holes were born from dense clouds of cold gas and dust, which agglomerates into stars if massive that they were destined to collapse quickly. These primordial black holes then grew, attracting gas around them which collapsed to form the first stars in dwarf galaxies. As the Universe expanded, these black holes quickly combined with others to form supermassive black holes, formant (In intonation, changes in fundamental frequency are perceived as variations in…) also larger galaxies.
The discovery of this pair of black holes was made possible thanks to archived data collected by the telescope (A telescope, (from the Greek tele meaning “far” and skopein meaning…) Gemini North in Hawaii. Using a spectrograph to decompose the light (Light is all electromagnetic waves visible to the eye…) stars in distinct colors, scientists identified lights coming from stars accelerating around black holes. There galaxy (A galaxy is, in cosmology, an assembly of stars, gas, dust and…) B2 0402+379, a “fossil cluster”, results from the merger of an entire cluster of stars and gas into a single gigantic galaxy.
Researchers believe that the merging of black holes within merging galaxies occurs by entering orbits around each other, then gradually moving closer together as their dance dissipates angular momentum by accelerating neighboring stars ( see explanation below). However, this pair of black holes, due to their gigantic mass, appears to have exhausted all the material that could slow them down, leaving their merger pending.
The researchers plan additional investigations into the core of B2 0402+379 to study the amount of gas present, providing additional insight into whether supermassive black holes may merge in the future, or whether, instead, they will remain in existence forever. duo.
The dissipation of angular momentum in supermassive black hole systems
The concept of angular momentum dissipation is essential for understanding the evolution of supermassive black hole binary systems and their eventual merger. The angular momentum, in physique (Physics (from the Greek φυσις, nature) is etymologically the…), is a measure of how much an object rotates around a point. In the context (The context of an event includes the circumstances and conditions surrounding it; the…) supermassive black holes orbiting each other, it plays a crucial role in the dynamic (The word dynamic is often used to designate or qualify that which relates to movement. It…) of their interaction (An interaction is an exchange of information, affects or energy between two agents within…).
When two black holes approach each other in a galaxy, they begin to attract each other due to their strong gravity. In orbit around each other, they form a binary system (The binary system is a numbering system using base 2. We call it…). However, for these black holes to merge, they must first come close enough. For this, the system must loseenergy (In the common sense, energy refers to everything that allows us to carry out work, produce energy, etc.) and angular momentum. Angular momentum keeps them orbiting at a certain distance, and without its dissipation they would continue to rotate indefinitely without ever merging.
Dissipation of angular momentum can occur in several ways.
A key method in galactic environments involves dynamic interaction with neighboring stars. As orbiting black holes approach stars in their host galaxy, their gravitational forces disrupt stellar orbits. These interactions can propel certain stars to higher speeds, ejecting them from the galactic system, while allowing black holes to come closer. This process transfers part of the angular momentum of the binary system to neighboring stars, thereby reducing the total angular momentum of the black holes and allowing gradual rapprochement.
Another method of dissipating angular momentum, especially relevant at very close distances, is the emission of gravitational waves. When black holes reach sufficient proximity, the intense warping of spacetime around them generates gravitational waves that can be energetic enough to carry with them a sufficient portion of the system’s energy and angular momentum, allowing for black holes to finally merge.
Angular momentum dissipation is therefore a fundamental process that allows supermassive black holes to come together and merge, a phenomenon that has profound implications for our understanding of the evolution of galaxies and the structure of the Universe.
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