The early universe was crammed with stars 10,000 times the size of our sun, new study suggests

An illustation showing a twinkling burst of starlight at the center of a turbulent field of crackling orange radiation and glowing black holes. (Image credit: ESA)

The first stars in the cosmos may have topped out at over 10,000 times the mass of the sun, roughly 1,000 times bigger than the biggest stars alive today, a new study has found. 

Nowadays, the biggest stars are 100 solar masses. But the early universe was a far more exotic place, filled with mega-giant stars that lived fast and died very, very young, the researchers found.

And once these doomed giants died out, conditions were never right for them to form again.

Related: Our expanding universe: Age, history & other facts

The cosmic Dark Ages

More than 13 billion years ago, not long after the Big Bang, the universe had no stars. There was nothing more than a warm soup of neutral gas, almost entirely made up of hydrogen and helium. Over hundreds of millions of years, however, that neutral gas began to pile up into increasingly dense balls of matter. This period is known as the cosmic Dark Ages.

In the modern day universe, dense balls of matter quickly collapse to form stars. But that’s because the modern universe has something that the early universe lacked: A lot of elements heavier than hydrogen and helium. These elements are very efficient at radiating energy away. This allows the dense clumps to shrink very rapidly, collapsing to high enough densities to trigger nuclear fusion – the process that powers stars by combining lighter elements into heavier ones.

But the only way to get heavier elements in the first place is through that same nuclear fusion process. Multiple generations of stars forming, fusing, and dying enriched the cosmos to its present state.

Without the ability to rapidly release heat, the first generation of stars had to form under much different, and much more difficult, conditions. 

Stars form when clouds of dust and gas collapse, triggering nuclear fusion inside the dense balls of material. (Image credit: NASA/ESA/Hubble Heritage Team (STScI/AURA))

Cold fronts

To understand the puzzle of these first stars, a team of astrophysicists turned to sophisticated computer simulations of the dark ages to understand what was going on back then. They reported their findings in January in a paper published to the preprint database arXiv and submitted for peer review to the Monthly Notices of the Royal Astronomical Society.

The new work features all the usual cosmological ingredients: Dark matter to help grow galaxies, the evolution and clumping of neutral gas, and radiation that can cool and sometimes reheat the gas. But their work includes something that others have lacked: Cold fronts – fast-moving streams of chilled matter – that slam into already formed structures.

The researchers found that a complex web of interactions preceded the first star formation. Neutral gas began to collect and clump together. Hydrogen and helium released a little bit of heat, which allowed clumps of the neutral gas to slowly reach higher densities.

But high-density clumps became very warm, producing  radiation that broke apart the neutral gas and prevented it from fragmenting into many smaller clumps. That means stars made from these clumps can become incredibly large.

This artist's impression shows the blast from a heatwave detected in a massive, forming star.

This artist's impression shows the blast from a heatwave detected in a massive, forming star. (Image credit: Katharina Immer/JIVE)

Supermassive stars

These back-and-forth interactions between radiation and neutral gas led to massive pools of neutral gas– the beginnings of the first galaxies. The gas deep within these proto-galaxies formed rapidly spinning accretion disks – fast-flowing rings of matter that form around massive objects, including black holes in the modern universe. 

Meanwhile, on the outer edges of the proto-galaxies, cold fronts of gas rained down. The coldest, most massive fronts penetrated the proto-galaxies all the way to the accretion disk.

These cold fronts slammed into the disks, rapidly increasing both their mass and density to a critical threshold, thereby allowing the first stars to appear.

Those first stars weren't just any normal fusion factories. They were gigantic clumps of neutral gas igniting their fusion cores all at once, skipping the stage where they fragment into small pieces. The resulting stellar mass was huge.

Those first stars would have been incredibly bright and would have lived extremely short lives, less than a million years. (Stars in the modern universe can live billions of years). After that, they would have died in furious bursts of supernova explosions. 

Those explosions would have carried the products of the internal fusion reactions – elements heavier than hydrogen and helium – that then seeded the next round of star formation. But now contaminated by heavier elements, the process couldn't repeat itself, and those monsters would never again appear on the cosmic scene.

Originally published on LiveScience.com.

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Paul Sutter
Space.com Contributor

Paul M. Sutter is an astrophysicist at SUNY Stony Brook and the Flatiron Institute in New York City. Paul received his PhD in Physics from the University of Illinois at Urbana-Champaign in 2011, and spent three years at the Paris Institute of Astrophysics, followed by a research fellowship in Trieste, Italy, His research focuses on many diverse topics, from the emptiest regions of the universe to the earliest moments of the Big Bang to the hunt for the first stars. As an "Agent to the Stars," Paul has passionately engaged the public in science outreach for several years. He is the host of the popular "Ask a Spaceman!" podcast, author of "Your Place in the Universe" and "How to Die in Space" and he frequently appears on TV — including on The Weather Channel, for which he serves as Official Space Specialist.

  • Unclear Engineer
    This article does not mention what happened to those huge stars at the "ends of their lives," other than to say that they presumably went supernova and scattered heavier elements into the cosmos.

    But, wouldn't they have become back holes? How big (massive) are the black holes resulting from supernovas of stars with 10,000 times the mass of our Sun? Do we see evidence of that number of black holes in the early universe? Do we see evidence of that number of early black holes in obsevations of the current local universe - either individually or as merged supermassive black holes, now?
    Reply
  • billslugg
    I believe so. I remember reading that JWST observations included way more SMBHs than they expected.
    Reply
  • rod
    The reference paper link is a 17-page PDF report to read :) 'First emergence of cold accretion and supermassive star formation in the early universe', Preprint 14 March 2023, "1 INTRODUCTION More than 200 quasars have been observed at 𝑧 ~> 6 (Mortlock et al. 2011; Bañados et al. 2018; Matsuoka et al. 2019; Wang et al. 2021), indicating that Supermassive Black Holes (SMBHs) with 𝑀BH = 10^8-10 Msun already exist in the early universe. The most distant quasar observed so far is located at 𝑧 = 7.54 (Bañados et al. 2018), which corresponds to the cosmic age of 0.7 Gyr. Theoretically, it is challenging to form SMBHs in such an early universe (Inayoshi et al. 2020). The BHs provided by Population (Pop) III stars are one of the possible candidates that will grow into the observed high-z SMBHs. Recent numerical simulations have shown that the Pop III stars appear with masses of 𝑀 = 10–10^3 Msun at 𝑧 ~ 20-30 (Hosokawa et al. 2012; Hirano et al. 2014, 2015; Susa et al. 2014; Hosokawa et al. 2016; Stacy et al. 2016; Sugimura et al. 2020), some of which finally collapse into BHs with negligible mass loss (Heger&Woosley 2002; Takahashi et al. 2018). To attain the observed mass of the SMBHs until 𝑧 = 7.5, the seed BH should maintain the Eddington accretion rate for the entire period of the corresponding cosmic age. However, the Eddington rate is hard to achieve due to the feedback associated with star formation and the mass accretion onto BHs (Johnson & Bromm 2007; Alvarez et al. 2009; Jeon et al. 2012)."

    My note. Some of the redshift numbers in the Introduction range 20-30 z when searching for Population III stars. "6 CONCLUSIONS We have studied the first emergence of the cold accretion, or the supersonic accretion flows directly coming into the halo centre, performing a suite of cosmological N-body + SPH simulations. Using the zoom-in technique, we have achieved sufficiently high spatial resolutions to study the detailed flow structure within halos with 𝑀halo ~ 10^7-8 Msun at the epochs of 𝑧 ~ 10-20."

    Perhaps JWST will see Population III stars or even 10^4 Msun stars. So far, none observed and shown in nature like we can observe M42 in Orion as an example. What we see in M42 is very different than the early universe in the simulations for Population III stars forming or SMBH forming. Even the CMBR lacks confirmed H-alpha and H1 21-cm line. The primordial gas clouds created during BBN need to be shown in nature. Work continues in this area as the reference paper shows. I will leave the comoving radial distances and space expanding faster than c velocity alone for the large redshifts reported in the paper where perhaps 10^4 Msun stars evolved and Population III stars :)
    Reply
  • rod
    FYI. I read about this in a bit earlier report too.

    The first stars may have held up to 100,000 times the mass of the sun, https://phys.org/news/2023-02-stars-held-mass-sun.html, 03-Feb-2023.

    So we have 10,000 solar mass stars, perhaps 100,000 solar mass stars in the early universe. Anyone here for a million solar mass stars or even a trillion :) This is good stuff :)
    Reply
  • Helio
    Their short lives would likely produce more and more SN, thus explaining the higher than expected metal levels back then. It will be interesting to see how these views develop with more JWST studies.
    Reply
  • Helio
    rod said:
    So we have 10,000 solar mass stars, perhaps 100,000 solar mass stars in the early universe. Anyone here for a million solar mass stars or even a trillion :) This is good stuff :)
    My guess is that the mass (not size) will drop closer to 1000. It’s been held that they had to be at least 200x more massive than the Sun, but 10,000x seems too extreme.

    Perhaps, in time, we will see a Pop IV star class for these Adam & Eve stars.
    Reply
  • murgatroyd
    rod said:
    The primordial gas clouds created during BBN need to be shown in nature.
    What is BBN?
    Reply
  • rod
    murgatroyd said:
    What is BBN?
    https://en.wikipedia.org/wiki/Big_Bang_nucleosynthesis
    Big Bang nucleosynthesis.
    Reply
  • Plato’s assistant
    Unclear Engineer said:
    This article does not mention what happened to those huge stars at the "ends of their lives," other than to say that they presumably went supernova and scattered heavier elements into the cosmos.

    But, wouldn't they have become back holes? How big (massive) are the black holes resulting from supernovas of stars with 10,000 times the mass of our Sun? Do we see evidence of that number of black holes in the early universe? Do we see evidence of that number of early black holes in obsevations of the current local universe - either individually or as merged supermassive black holes, now?


    It’s hard to know exactly… a common misconception is that the original matter that came from the big bang was hydrogen, or more specifically exactly how long it took what came from the Big Bang to become hydrogen… most likely as this matter became more and more dense and it became elements that were more and more complex… that yes this would lead to SMBHs at those density levels… but we also know, certain combinations of matter that don’t reach a high enough density level fast enough, can start to become cooler… it’s possible that this happens at larger star levels with earlier combinations; and it was more difficult to reach ”black hole“ density levels… then it is currently
    Reply
  • Plato’s assistant
    rod said:
    https://en.wikipedia.org/wiki/Big_Bang_nucleosynthesis
    Big Bang nucleosynthesis.

    I hadn’t realized you wrote this, this is basically what I was explaining in my response to his original question… it’s also possible that a BH is just a star that reaches a certain density level with a certain combination of complex elements; and that we’re just seeing the effects of it as a “black hole”… Ex. When complex matter becomes so dense in a single area we observe it as a black hole, and nothing is actually different at all… except the entirely of the star has been pulled beyond the funnel of space time… If this is the case, it is possible we might one day see a star lose enough mass and pop into existence from a black hole condition, as the radiation no longer has enough mass to be entirely shielded by the funnel of the fabric of space time…
    Reply