West LA Times

Supermassive black holes typically take billions of years to form. However, the James Webb Space Telescope is finding them not long after the Big Bang — before they should have had time to form.

UCLA astrophysicists have discovered that if dark matter decays, the photons it emits keep hydrogen gas hot enough for gravity to gather it into giant clouds and eventually condense it into a supermassive black hole. This discovery not only explains the existence of very early supermassive black holes but also supports the existence of a kind of dark matter capable of decaying into particles such as photons.

It takes a long time for supermassive black holes, like the one at the center of our Milky Way galaxy, to form. Typically, the birth of a black hole requires a giant star with the mass of at least 50 suns to burn out – a process that can take a billion years – and its core to collapse in on itself.

Even so, at only about 10 solar masses, the resulting black hole is far smaller than Sagittarius A*, found in our Milky Way galaxy with 4 million solar masses or other galaxies' billion-solar-mass supermassive black holes. Such gigantic black holes can form from smaller ones by accretion of gas and stars and mergers with other black holes over billions of years.

The James Webb Space Telescope's discovery of supermassive black holes near the beginning of time itself poses an intriguing question: How did these massive objects form so quickly? UCLA astrophysicists propose that dark matter kept hydrogen from cooling long enough for gravity to condense it into clouds big and dense enough to turn into black holes instead of stars. The finding is published in Physical Review Letters.

“How surprising it has been to find a supermassive black hole with a billion solar mass when the universe itself is only half a billion years old,” said senior author Alexander Kusenko, professor of physics and astronomy at UCLA. “It’s like finding a modern car among dinosaur bones and wondering who built that car in prehistoric times.”

Some astrophysicists have suggested that large gas clouds could collapse directly into supermassive black holes, bypassing stellar burning, accretion, and mergers. However, gravity tends to pull large gas clouds together into small halos rather than forming one large cloud due to rapid cooling.

“How quickly the gas cools has much to do with molecular hydrogen,” said first author Yifan Lu. “Hydrogen atoms bonded together dissipate energy when encountering loose hydrogen atoms; these molecules become cooling agents by absorbing thermal energy and radiating it away.” Hydrogen clouds in the early universe had too much molecular hydrogen which led them to cool quickly and form small halos instead of large clouds.

Lu and postdoctoral researcher Zachary Picker wrote code calculating all possible processes under this scenario and discovered additional radiation could heat gas sufficiently while dissociating hydrogen molecules thus altering how gas cools.

“If you add radiation in certain energy ranges,” Lu explained, “it destroys molecular hydrogen creating conditions preventing fragmentation.”

Dark matter's nature remains elusive; however particle theorists speculate unstable particles within dark matter might decay into photons — particles essential for maintaining sufficient heat during cloud formation preventing premature cooling allowing eventual formation into supermassive blackholes

“This could be why we find early-onset supermassive Black Holes," Picker stated adding optimistically "If these formed via collapsing Gas Clouds maybe required additional Radiation comes from unknown Dark Sector Physics."

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