New Delhi: Since the James Webb Space Telescope began operations in December 2024, the deep-field observations have revealed hundreds of small, red points
of light peppered among the most distant stars and galaxies. These mysterious ‘Little Red Dots (LRDs)’ appear when the universe was only several hundred million years old, and vanish about a billion years after the Big Bang. Initial observations suggested that they were massive galaxies, considering that they were visible from 13 billion lightyears away, but conventional theories of galaxy formation cannot explain how they appeared so soon after the Big Bang.
Detailed analysis of the images captured by James Webb Space Telescope over two years by scientists at the Cosmic Dawn Centre at the Neils Bohr Institute has identified the dots as young black holes, containing far fewer mass than previous estimates. These objects crucially, eliminate the need for exotic mechanisms of formation, including direct collapse of black holes from molecular clouds, and the collapse of dark stars, that are vast, diffuse, luminous objects powered by matter and antimatter destroying each other, collapsing into massive black holes after running out of dark matter. The black holes are nested within dense cocoons of gas that they are consuming as they grow.
Black holes are ‘messy’ eaters
The tortured gas falling in towards the event horizon reaches millions of degrees and emits intense radiation. This head shines through the surrounding cocoon of gas, producing the distinctive red colour observed by Webb. Black holes are not very efficient at accretion. While the event horizon remains small, the infalling gas heats up dramatically and radiates energy. Because of the rotation of the accretion disk and its magnetic fields, material gets expelled along the poles instead of falling in, making the black holes messy eaters.
Each of the Little Red Dots contain up to 10 million solar masses, with diameters of around 10 million km, and are among the smallest black holes detected at high redshifts. The discovery explains how supermassive black holes reached up to a billion solar masses within 700 million years of the Big Bang. These young black holes were observed during a rapid growth phase, fuelled by the dense cocoons that provide abundant material for rapid expansion. This phase fills a gap in understanding early development of black holes, showing how they emerged and matured in the infancy of the Universe. The research has been published in Nature, and appeared on the cover.
