Astronomers find 1st evidence of heavy black hole seeds in the early universe

An illustration of a supermassive black hole with a mass billions of times that of the sun. Did these cosmic titans grow from massive black hole seeds?
An illustration of a supermassive black hole with a mass billions of times that of the sun. Did these cosmic titans grow from massive black hole seeds? (Image credit: NASA)

Astronomers may have discovered the first evidence of heavy black hole "seeds" in the early universe. 

These so-called seeds could help explain how some supermassive black holes with masses equivalent to millions, or even billions, times that of the sun could have grown quickly enough to exist less than 1 billion years after the Big Bang

Potentially, heavy black hole seeds are black holes with masses around 40 million time that of our sun. They are believed to form from the direct collapse of a massive cloud of gas, unlike your typical black hole that's born when a massive star reaches the end of its life and collapses under its own gravity. Galaxies theorized to host such heavy black hole seeds are referred to as Outsize Black Hole Galaxies (OBGs). 

These galaxies are likely very distant, seen with our telescope as they were when our 13.8 billion-year-old universe was somewhere around 400 million years old. And now, scientists might've finally identified one of these OBGs.

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The team, led by Center for Astrophysics Harvard & Smithsonian researcher, Akos Bogdán, first detected an object with a mass characteristic of black holes while investigating a quasar using the James Webb Space Telescope (JWST) and NASA's Chandra X-ray Observatory. Powered by supermassive black holes, quasars are extremely luminous, active hearts of galaxies. They can be so bright, in fact, that they outshine the combined light of every single star in the galaxy that hosts them.

The one studied by Bogdán and fellow researchers lives in a galaxy named UHZ1.

And, as it turned out, data from the JWST and Chandra regarding UHZ1 was consistent with what would be expected from an OBG. The team found X-ray emissions by tapping into Chandra, and these emissions indicated a feeding or "accreting" black hole associated with the quasar, which was particularly compelling in identifying the surrounding galaxy as an OBG. 

The researchers also compared their observations to simulations of the rapid growth of heavy black hole seeds, finding that there was a good match between the two. The best fit they found during this comparison was with a 10,000-solar-mass seed growing over the course of several hundred million years. 

"Based on the excellent agreement between the observed multi-wavelength properties of UHZ1 with theoretical model template predictions, we suggest that UHZ1 is the first detected OBG candidate, subject to spectroscopic confirmation of its redshift," the authors wrote in a paper explaining the discovery. "Therefore, as the first OBG candidate, UHZ1 provides compelling evidence for forming heavy initial seeds from direct collapse in the early universe."

How heavy seeds give black holes a growth boost

The tremendous size of supermassive black holes doesn't trouble scientists too much. That's because these cosmic titans have had billions of years to grow by feeding on surrounding gas and dust as well as by merging with other black holes. The one at the heart of the Milky Way, Sagittarius A* (Sgr A*), for instance had enough time to grow to around 4.5 million times the mass of the sun. The black hole at the heart of a galaxy named M87 managed to get even bigger, sitting at around 5 billion times the mass of our star. 

But because these growth mechanisms are estimated to take place over billions of years, the discovery of similarly supermassive black holes that existed between just 500 million years to a mere billion years after the Big Bang is challenging. Those mass-gathering methods wouldn't have had the time needed to result in such gargantuan black holes. Yet, that's exactly what astronomers studying the early universe with the JWST and other instruments have been finding.

"It's like seeing a family walking down the street, and they have two six-foot teenagers, but they also have with them a six-foot tall toddler. That's a bit of a problem; how did the toddler get so tall?" John Reagan, a research fellow at Maynooth University, who was not involved in this research, told "And it's the same for supermassive black holes in the universe. How did they get so massive so quickly?"

Well, one theory is that these black holes got a head start in their mass accretion processes by growing from smaller black hole "seed."

There are two predominant lines of thought in this regard. On one hand, experts suggest supermassive black holes could've grown from light black hole seeds with masses around 10 to 100 times that of the sun. Those light seeds would theoretically be born via the standard mechanism of stellar-mass black hole creation, namely the death and collapse of the universe's first generation of stars.  

On the other hand, early supermassive black holes could've grown from heavy seed black holes with huge masses around 100,000 times the mass of the sun. These would've formed directly from the collapse of massive clouds of matter, thus skipping the "star stage" of other black holes entirely. Astronomers refer to such black holes as direct collapse black holes (DCBHs).

These DCBHs could then grow alongside galactic mergers, which were commonplace in the early universe, that would also bring supplies of gas and dust for these voids feast upon. Then eventually, other black holes might've collided and merged with those. 

Regan compares this to the six-foot-tall toddler being born with a length of three feet. It is still a bit confusing (and perhaps a tad disturbing), but it better explains how the toddler reached the size of an adult so rapidly, at least more easily than if the toddler started off with the length of an average infant. 

Other smaller black hole seeds aren't expected to give rise to OBGs, so the identification of UHZ1 as such a galaxy thus supports the existence of heavy black hole seeds and lends credibility to their role in early supermassive black hole growth.

The authors themselves point out the limitations of their research, however, and urge caution with extrapolating that the growth of the black hole within UHZ1 reached supermassive status. They also empathize that the possibility of such growth would depend heavily on the environment a potential seed finds itself in, with copious amounts of gas and dust necessary to support its growth. 

There is still a great deal more investigation that must take place before a population of heavy seed black holes can be confirmed and their connection to supermassive black holes in the infant universe can be established, but these findings at least represent a step in the right direction.

"As JWST detects more [distant and early] accreting black holes in the coming cycles, we plan to analyze those sources, investigate possible X-ray counterparts with Chandra, and develop a deeper understanding of OBGs and heavy seeding physics," the team concluded.

"This detection provides yet more evidence for the heavy seed scenario," Regan told "Taken together with other JWST black hole masses that have been observed, I would say that the weight of evidence is now pointing strongly towards a heavy seed scenario for supermassive black hole growth."

The team's research has been submitted to the Astrophysical Journal Letters and is currently published on the paper repository arXiv. 

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Robert Lea
Senior Writer

Robert Lea is a science journalist in the U.K. whose articles have been published in Physics World, New Scientist, Astronomy Magazine, All About Space, Newsweek and ZME Science. He also writes about science communication for Elsevier and the European Journal of Physics. Rob holds a bachelor of science degree in physics and astronomy from the U.K.’s Open University. Follow him on Twitter @sciencef1rst.

  • rod
    Very interesting reading. IMO, it still looks like SMBH in the early universe, remain challenging to explain using what we see operating in nature today, a very different nature operating *in the beginning* :)

    I read another recent review on this OBG at the site.

    Radio Emission From a z= 10.3 Black Hole in UHZ1,
    "The recent discovery of a 4 × 10^7 M⊙ black hole (BH) in UHZ1 at z= 10.3, just 450 Myr after the big bang, suggests that the seeds of the first quasars may have been direct-collapse black holes (DCBHs) from the collapse of supermassive primordial stars at z∼ 20. This object was identified in James Webb Space Telescope (JWST) NIRcam and Chandra X-ray data, but recent studies suggest that radio emission from such a BH should also be visible to the Square Kilometer Array (SKA) and the next-generation Very Large Array (ngVLA). Here, we present estimates of radio flux for UHZ1 from 0.1 - 10 GHz, and find that SKA and ngVLA could detect it with integration times of 10 - 100 hr and just 1 - 10 hr, respectively. It may be possible to see this object with VLA now with longer integration times. The detection of radio emission from UHZ1 would be a first test of exciting new synergies between near infrared (NIR) and radio observatories that could open the era of z∼ 5 - 15 quasar astronomy in the coming decade."

    The reported "Potentially, heavy black hole seeds are black holes with masses around 40 million time that of our sun. They are believed to form from the direct collapse of a massive cloud of gas, unlike your typical black hole that's born when a massive star reaches the end of its life and collapses under its own gravity. Galaxies theorized to host such heavy black hole seeds are referred to as Outsize Black Hole Galaxies (OBGs)."

    My note. *Direct collapse of a massive cloud of gas* is a different mechanism used than the other report where possible direct collapse of massive stars with redshifts near 20 is considered. These would likely be a massive Population III star, something not observed in nature, like the seed used in the report, *a massive cloud of gas* to start forming SMBH seen and documented today.

    Using Ned Wright cosmology calculator,
    z=10.3, "The age at redshift z was 0.459 Gyr." "The light travel time was 13.263 Gyr." "The comoving radial distance, which goes into Hubble's law, is 9719.9 Mpc or 31.702 Gly."

    At the comoving radial distance from Earth today, space is expanding 2.2371032E+00 or more than 2.2x c velocity using H0 = 69 km/s/Mpc.
  • Unclear Engineer
    So, do they believe that gas clouds can collapse into black holes without igniting fusion and causing a star to form? Or does a star form, but inside an event horizon so we cannot see it? A big enough ball of gas could still be quite cold when it becomes a black hole, at least in theory. Does that seem to work out, practically, given the density fluctuations apparent in the CMBR?
  • Torbjorn Larsson
    @Unclear Engineer: It's in the paper.

    "Heavy seed models, on the other hand, propose the formation of 10^4 − 10^5 M⊙ seeds in several possible ways. First, heavy seeds could result from the direct collapse of pre-galactic gas disks (Loeb & Rasio 1994; Volonteri & Rees 2005; Lodato & Natarajan 2006; Begelman et al. 2006; Lodato & Natarajan 2007) leading on to growth transiting through the OBG stage (Agarwal et al. 2013). A second pathway involves rapid, amplified early growth of originally light seeds that may end up in conducive cosmic environments, such as gas-rich, dense nuclear star clusters (Alexander & Natarajan 2014). Additionally, rapid mergers of light remnants in the early nuclear star clusters could also lead to the formation of heavy seeds at high redshifts as proposed by Devecchi & Volonteri (2009) as well as the runaway collapse of nuclear star clusters as proposed by (Davies et al. 2011). In addition to these more conventional theoretical seeding models, primordial black holes (PBHs, Hawking 1971) that form in the infant Universe have also been explored as potential candidates to account for the origin of initial seeds for SMBHs in the very early Universe (see Cappelluti et al. 2022 and references therein)."

    The primordial black hole model directly from the weak cosmic background fluctuations are AFAIU disfavored by modern observations of the background as well as by microlensing (and other) observations not finding any.
  • billslugg
    Sounds like a big enough cloud of primordial gas can collapse to a Black Hole without passing through the star stage, despite the outward pressure of the heat of compression.
  • Unclear Engineer
    spacetimedimen said:
    I understand that you saw an elliptically shaped, shiny silvery object. You believe that the sun glinting off a commercial jet aeroplane somehow was modified by a layer of moist air near you to create the appearance of a solid object.

    Your explanation is certainly possible, and it is a good example of how atmospheric conditions can sometimes play tricks on our eyes. However, it is also possible that you saw something else entirely.
    And in my experience, I know that I saw an actual thing not a UAP phenomenon I saw it very clearly and at that time of the night there were no jets or any aircraft flying around it was a clear dark night. I believe I saw something not made by a human.

    billslugg said:
    Sounds like a big enough cloud of primordial gas can collapse to a Black Hole without passing through the star stage, despite the outward pressure of the heat of compression.
    It seems like it would depend on how well separated the cloud became from other clouds, other masses. A not very dense but dimensionally immense gas cloud could be a black hole without collapsing. So if it eventually collapsed, those of us on the outside would not be able to witness it happen.

    So, the question becomes is it realistic for a cloud to be dense enough, big enough, and separate enough to do that in the environment theorized for the universe following the release of the CMBR?
  • Unclear Engineer

    I think you accidentally quoted from 2 different threads when you replied to me here, then replied to each quoted subject in 2 successive posts in this thread.

    The stuff about UAP observations belongs in the thread in the Astronomy Section
  • billslugg
    I see what happened. At 3:46PM y ou quoted Spacetime and inadvertantly included a UAP qoute to which I responded. I'll just delete my comment.