How did supermassive black holes end up at the center of every galaxy? A while back, it wasn't that hard to explain: That's where the highest concentration of matter is, and the black holes had billions of years to feed on it. But as we've looked ever deeper into the Universe's history, we keep finding supermassive black holes, which shortens the timeline for their formation. Rather than making a leisurely meal of nearby matter, these black holes have gorged themselves in a feeding frenzy.

With the advent of the Webb Space Telescope, the problem has pushed up against theoretical limits. The matter falling into a black hole generates radiation, with faster feeding meaning more radiation. And that radiation can drive off nearby matter, choking off the black hole's food supply. That sets a limit on how fast black holes can grow unless matter is somehow fed directly into them. The Webb was used to identify early supermassive black holes that needed to have been pushing against the limit for their entire existence.

But the Webb may have just identified a solution to the dilemma as well. It has spotted a black hole that appears to have been feeding at 40 times the theoretical limit for millions of years, allowing growth at a pace sufficient to build a supermassive black hole.

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Enlarge / Some of the galaxies in the JADES images. (credit: NASA, ESA, CSA, M. Zamani)

One of the things that the James Webb Space Telescope was designed to do was look at some of the earliest objects in the Universe. And it has already succeeded spectacularly, imaging galaxies as they existed just 250 million years after the Big Bang. But these galaxies were small, compact, and similar in scope to what we'd consider a dwarf galaxy today, which made it difficult to determine what was producing their light: stars or an actively feeding supermassive black hole at their core.

This week, Nature is publishing confirmation that some additional galaxies we've imaged also date back to just 300 million years after the Big Bang. Critically, one of them is bright and relatively large, allowing us to infer that most of its light was coming from a halo of stars surrounding its core, rather than originating in the same area as the central black hole. The finding implies that it formed through a continuing burst of star formation that started just 200 million years after the Big Bang.

Age checks

The galaxies at issue here were first imaged during the JADES (JWST Advanced Deep Extragalactic Survey) imaging program, which includes part of the area imaged for the Hubble Ultra Deep Field. Initially, old galaxies were identified by using a combination of filters on one of Webb's infrared imaging cameras.

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Enlarge / Image of Epsilon Indi A at two wavelengths, with the position of its host star indicated by an asterisk. (credit: T. Müller (MPIA/HdA), E. Matthews (MPIA))

We have a couple of techniques that allow us to infer the presence of an exoplanet based on its effects on the light coming from its host star. But there's an alternative approach that sometimes works: image them directly. It's much more limited, since the planet has to be pretty big and orbiting far away enough from its star to avoid having light coming from the planet swamped by the far more intense starlight.

Still, it has been done. Massive exoplanets have been captured relatively shortly after their formation, when the heat generated by the collapse of material into the planet causes them to glow in the infrared. But the Webb telescope is far more sensitive than any infrared observatory we've ever built, and it has managed to image a relatively nearby exoplanet that's roughly as old as the ones in our Solar System.

Looking directly at a planet

What do you need to directly image a planet that's orbiting a star light-years away? The first thing is a bit of hardware called a coronagraph attached to your telescope. This is responsible for blocking the light from the star the planet is orbiting; without it, that light will swamp any other sources in the exosolar system. Even with a good coronagraph, you need the planets to be orbiting at a significant distance from the star so that they're cleanly separated from the signal being blocked by the coronagraph.

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Enlarge (credit: NASA, ESA, CSA, Joseph Olmsted (STScI))

Supermassive black holes appear to be present at the center of every galaxy, going back to some of the earliest galaxies in the Universe. And we have no idea how they got there. It shouldn't be possible for them to grow from supernova remnants to supermassive sizes as quickly as they do. And we're not aware of any other mechanism that could form something big enough that extreme growth wouldn't be necessary.

The seeming impossibility of supermassive black holes in the early Universe was already a bit of a problem; the James Webb Space Telescope has only made it worse by finding ever-earlier instances of galaxies with supermassive black holes. In the latest example, researchers have used the Webb to characterize a quasar powered by a supermassive black hole as it existed approximately 750 million years after the Big Bang. And it looks shockingly normal.

Looking back in time

Quasars are the brightest objects in the Universe, powered by actively feeding supermassive black holes. The galaxy surrounding them feeds them enough material that they form bright accretion disks and powerful jets, both of which emit copious amounts of radiation. They're often partly shrouded in dust, which glows from absorbing some of the energy emitted by the black hole. These quasars emit so much radiation that they ultimately drive some of the nearby material out of the galaxy entirely.

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