Webb Finds the Strongest Case Yet for 'Black Hole Stars'
Webb's deepest spectrum of a 'little red dot,' GLIMPSE-17775, points to a supermassive black hole cloaked in dense gas, a possible answer to two cosmic puzzles.
One of the universe’s stranger puzzles may have an answer. Astronomers using the James Webb Space Telescope say they have the strongest evidence yet that a class of mysterious objects from the early cosmos, the so-called “little red dots,” are in fact “black hole stars”: supermassive black holes swaddled in dense, glowing gas.
The finding, announced this month by NASA and the European Space Agency, centers on a single object catalogued as GLIMPSE-17775, seen as it was just 1.8 billion years after the Big Bang. By capturing the deepest spectrum yet taken of such a dot, a team led by Vasily Kokorev of the University of Texas at Austin found a pattern of light that fits one model far better than the alternatives.
The trick was a cosmic magnifying glass. Webb looked at GLIMPSE-17775 through the gravity of a foreground galaxy cluster, Abell S1063, which bends and brightens the light of objects behind it. In the magnified spectrum the team read telltale signatures, electron scattering, fluorescence and a dense thicket of iron lines they nicknamed an “iron forest,” pointing to a black hole feeding inside a thick cocoon of partially ionised gas rather than an ordinary galaxy full of stars.
If the interpretation holds, it would help solve two problems at once. Little red dots have baffled astronomers since Webb began finding them in number: they are too compact and oddly coloured to be normal galaxies. And the early universe holds supermassive black holes far bigger than simple models say should exist so soon after the Big Bang. A gas-cloaked, rapidly growing “black hole star” phase could be the missing step. It is, the researchers stress, one strongly favoured reading of one object, not a closed case.
What makes it persuasive is the spectrum’s depth, the kind of detail only Webb, and a lucky alignment of gravity, can deliver. The same telescope that mapped the weather on a distant gas giant is now reading the chemistry around a black hole that lit up when the universe was young. More dots, and more spectra, will tell whether GLIMPSE-17775 is a template or an exception. The ESA also detailed the result.
