One of the earliest stars to form identified?

Astronomers have detected an extremely unusual star that they believe is a stellar fossil, or remnant, of one of the universe’s very first stars.

The star, named AS0039, is located in the Sculptor dwarf galaxy around 290,000 light-years from us. This stellar remnant has the lowest concentration of metal, particularly iron, of any star measured outside the Milky Way. The researchers think that finding is evidence that the remnant is a direct descendent of one of the universe’s earliest stars, which contained very little metal.

The team found that the primordial parent star of AS0039 would have been around 20 solar masses and likely died in a hypernova — a stellar explosion 10 to 100 times more powerful than a regular supernova.

A hypernova. Image: Shutterstock

The discovery may reveal new information about the universe’s first stars, which have never been directly or indirectly observed until now. “AS0039 has such an unusual chemical composition that it enables us to probe the nature of the first stars and, in particular, their stellar mass,” study co-author Mike Irwin, an astronomer at the University of Cambridge in England, told Live Science.

The very first stars

Though all stars are balls of hot gas called plasma, fueled by the fusion of elements in the core, they are also extremely diverse; they can range widely in size and color. But all stars can be classified into three distinct groups — Population I, Population II and Population III — based on their chemical composition, or metallicity.

Population I stars, like the sun and most other stars in the observable universe, have high metal content, especially iron, and are rich in relatively heavy elements, like calcium and magnesium. Population II stars, such as AS0039, are much rarer; these metal-poor stars contain only trace amounts of heavy elements. Population III stars, which have never been seen, are almost totally metal-free and have zero heavy elements.

Although Population III stars have never been detected, astronomers know that the very first stars born in the universe would have been Population III stars, Irwin said.

During nuclear fusion, hydrogen atoms are fused together into helium, which releases an enormous amount of energy. Most stars ​​— those up to around 1.4 solar masses — slowly use up their hydrogen fuel until there is none left, swell up to red giants and eventually collapse into white dwarfs.

However, larger stars quickly use up their hydrogen and instead start to fuse helium into carbon and, eventually, carbon into iron, which is the heaviest element a star can create. Eventually, these large stars become too dense and collapse in on themselves and explode in a supernova, which not only disperses the star’s elements into the surrounding space but also releases enough energy to create elements heavier than iron.

New stars are often birthed in the clouds of gas left behind from previous stars, so when they form, they take in some of the metal and heavy elements from the exploded stars that came before them. As a result, all the stars observed today are Population I or II stars, because they formed from the leftovers of the stars that came before them.

However, the first stars in the universe, Population III stars, formed from pure hydrogen, which was the first element created after the Big Bang, Irwin said. “Population III stars are defined to be the first generation of stars to have formed in the universe and hence were formed from zero metallicity.”

These primary stars also lacked heavy elements because no supernovas had created them.

Hypernova offspring

When researchers found AS0039, they were amazed at how metal-poor it was, even compared with other Population II stars.

AS0039 has the lowest metal concentration of any star studied outside our own galaxy, as well as the lowest carbon concentration of any star ever studied in the universe. It also has unusual ratios of heavier elements, particularly magnesium and calcium, in very low quantities. These findings suggest that AS0039 may be a second-generation star that formed out of the remains of a Population III star.

Computer simulations suggested the Population III star that birthed AS0039 likely died in a powerful hypernova explosion. “We believe that Population III stars were generally more massive than stars that we see today, so it would not be surprising if a Population III star ended up as a hypernova,” Irwin said.

The researchers hope the discovery of AS0039 will help astronomers locate more second-generation metal-poor Population II stars, which would, in turn, shed light on the size and distribution of the Population III stars and the role they played in turning the early hydrogen-filled universe into the one we see today.

“AS0039 shows that it is possible to learn about the properties of Population III stars and signposts the way to finding more examples,” Irwin said. “This is vital in helping us to understand how the universe evolved to what we observe today.”

The study was published online July 13 in The Astrophysical Journal Letters.

See more here: livescience.com

Header image: NASA Wmap science team

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Comments (12)

  • Avatar

    Geraint Hughes

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    Stars are not “hot balls of gas” The surface of stars is super hot, super compressed Liquid Metallic Hydrogen, which is why they emit as condensed matter with the spectrums that they do, this fact explains their magnetospheres and also why they behave as liquids when their surfaces are observed.

    Reply

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    Jerry Krause

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    Hi Geraint and PSI Readers,

    “The surface of stars is super hot, super compressed Liquid Metallic Hydrogen”. Geraint, you are correct when you write this. However, when you wrote “Stars are not “hot balls of gas”, you are absolutely WRONG!!!

    For what COMPRESSES the hot liquid metallic hydrogen??? I believe you know that it is the gaseous hydrogen atoms above this surface.to which you refer and probably as well as a thick layer of gaseous hydrogen which has approximately the same DENSITY as liquid hydrogen at about 4 Kevin, the temperature of liquid He with a vapor pressure near one atm.

    I came to this conclusion when I began reading about the giant gaseous planets Jupiter and the planets beyond whose density was much less than that of the mineral, solid planets closer to the Sun. For when the authors, writing about these gaseous planets, wrote about their surfaces I was confused as I questioned: How can a GAS have a SURFACE???

    Then I finally remembered that Richard Feynman had taught his students: “all things are made of atoms–little particles that move around in perpetual motion, attracting each other when they are a little distance apart, but repelling upon being squeezed into one another.” And in giant gas planets and stars, we know the force squeezing the atoms into one another is that of GRAVITY…But I believe we know (understand) that gravity cannot MUCH squeeze the atoms into each other because the repulsion between atoms is greater than the force of gravity. Hence, there comes a point where the Density in the interior of a giant planet or star (no matter how great the temperature) becomes only a little less than that of the liquid gas at a much lower temperature.

    However the hot balls of gas still remain a GAS because there is NO ATTRACTION BETWEEN ATOMS holding them together.

    Have a good day, Jerry

    Reply

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    Geraint Hughes

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    Jerry, are you even qualified? It is well known the cores of the Jupiter and Saturn are also liquid metallic hyrdrogen, look it up.

    With the sun it is not just the cores, but its entirety, It is the gravity pulling them down and compressing them just like the Air on Earth is at higher pressure at the surface compared to higher up. The Sun surface is liquid metallic hydrogen, to suggest it is gas is to completely ignore the fact that hydrogen gas however hot, does not emit in the spectrum of the sun. However, liquid metallic hydrogen does.

    Reply

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      Jerry Krause

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      Hi Geraint,

      Thank you for reading my comment and replying.

      Please give me and the PSI Readers a reference for whomever on the planet EARTH has directly observed even a tiny Bit of liquid metallic hydrogen!!!

      Have a good day, Jerry

      Reply

      • Avatar

        Geraint Hughes

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        https://www.sciencealert.com/hydrogen-has-been-turned-into-a-metal-for-the-first-time-ever

        Theres a nice graph of the phases here.
        https://www.extremetech.com/wp-content/uploads/2016/08/082016_hydrogen_graph_free.png

        https://www.researchgate.net/publication/7568062_Observability_of_a_Projected_New_State_of_Matter_A_Metallic_Superfluid Ancient knowledge know. 2005

        https://arxiv.org/ftp/arxiv/papers/2109/2109.11104.pdf Theres actually quite a lot on this material. It is now commonly believed this substance is at teh centre of saturn and jupiter. Big Balls of gas is 100 year old wives tale thinking.

        Reply

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        Jerry Krause

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        Hi Geraint and PSI Readers,

        The following is from Geraint’s link to Physical Review Letters: ” “It was recently suggested that liquid metallic hydrogen could form two new and unusual dissipationless quantum states, namely, the metallic superfluid and the superconducting superfluid. Liquid metallic hydrogen is projected to occur only at an extremely high pressure of about 400 GPa, with pressures on hydrogen of 320 GPa having already been reported. The issue to be addressed is whether this state could be experimentally observable in principle. We propose four experimental probes for detecting it.”

        Has it been experimentally observed yet. No!!! This article only PROPOSES FOUR EXPERIMENTAL methods by which it might be DETECTED.

        And because you, Geraint, do not reference evidence that any of these four proposes actually worked, I have to assume they haven’t yet worked.

        Have a good day, Jerry

        Reply

      • Avatar

        Jerry Krause

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        Hi PSI Readers,

        As a chemist I need to review a reason why hydrogen maybe should be a METAL. It is called the PERIODIC LAW OF THE ELEMENTS which groups elements according to their physical and chemical properties.

        All elements, except hydrogen, seem to fit this pattern if hydrogen is placed in Group 1a. For in some ways hydrogen seems to fit the pattern of Group !a elements (lithium, sodium, potassium, etc) which are metals and conduct electricity in the liquid and solid phase states (phases). However, when hydrogen gas was cooled to its liquid state, it was discovered that its liquid state did not conduct electricity. However, this observed fact was not known until long after hydrogen had been placed in Group 1a.

        Instead, hydrogen seems to better fit inGroup 7a elements (fluorine, chlorine, etc.); which at normal room temperatures are gases, like hydrogen and do not conduct electricity in their liquid states, when cooled, like hydrogen.

        Have a good day, Jerry

        Reply

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    Andy

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    Stars are gas-balls not liquids guys! Arthur Clarke hypothesised the core of Jupiter could be a mega-carat diamond due to the amount of carbon in its atmosphere.

    Reply

    • Avatar

      Geraint Hughes

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      Andy, stars are liquid metallic hydrogen balls, at least on the surface

      Reply

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    Tom O

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    This article, like most that comes from astronomy these days, is so based on theories developed from theories developed from theories developed from theories that may have been developed from observable fact. Nothing but supposition and wishful thinking connects the first to the last. A pure and absolute example of what I like to refer to as educated ignorance.

    Reply

    • Avatar

      Jerry Krause

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      Hi Robert and PSI Readers,

      This article is about stars in which fusion reactions of hydrogen nuclei produce helium nuclei and a great, great amount of energy which produces extreme temperatures within the star where the fusion reactions occur.

      But you Robert change the topic to gaseous planets as if there is sufficient energy to accelerate heavier nuclei of oxygen to near the speed of light according to the article you linked. So I was not surprised when I researched who the author of your article was and found he was a journalist who only wrote about scientific topics. Robert, I cannot believe what this author wrote is observed fact as it seems implied.

      Have a good day, Jerry

      Reply

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