What it is
How billion-solar-mass black holes formed within the first 700 million years of cosmic time, the period known as cosmic dawn, remains a puzzle: several scenarios have been proposed to seed and rapidly grow them, but direct observations of those mechanisms remain elusive. The authors present a source, MoM-BH*-1, seen 660 million years after the Big Bang, whose 4.5-hour JWST NIRSpec prism spectrum from the 'Mirage or Miracle' programme, together with an archival higher-resolution NIRSpec grating spectrum, shows singular properties: among the largest hydrogen Balmer breaks reported at any redshift, broad multi-peaked Hβ emission, and Balmer line absorption in several transitions. Its break strength of 7.7 lies firmly beyond what stars are expected to produce (a population made only of the strongest-breaking A-type stars would stay below 5). The authors model it as an enshrouded black hole, in which the break and the absorption come from extremely dense, turbulent gas forming a dust-free envelope around a supermassive black hole, and radiation from the black hole seems to dominate almost all the observed light.
Why it matters
This source may be evidence of an early black hole embedded in dense gas, a configuration proposed to grow black holes rapidly by accreting faster than the Eddington limit. It also bears on the recently discovered 'little red dots', whose light has puzzled astronomers: if this source merged with its brighter neighbour, it would resemble one. The authors argue the redness comes from gas rather than dust, and the line shapes from scattering rather than motion, so black hole masses of such sources may be overestimated by orders of magnitude; for this object their estimates run from about 10^8.3 solar masses if the reddening were dust down to about 10^6 if the line widths come from scattering.
Underlined numbers link to their source. Every metric and quoted figure is listed under Sources and data below.
Filed underGalaxies: Formation, Evolution, Phenomena, Astrophysical Phenomena and Observations, Astrophysics and Star Formation Studies
