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Two-Faced Star With Helium and Hydrogen Sides Baffles Astronomers (theguardian.com) 64

Posted by BeauHD from the one-of-a-kind dept.
Astronomers have discovered a two-faced star and are baffled by its bizarre appearance. The Guardian reports: The white dwarf appears to have one side composed almost entirely of hydrogen and the other side made up of helium. It is the first time that astronomers have discovered a lone star that appears to have spontaneously developed two contrasting faces. The object, which is more than 1,000 light years away in the Cygnus constellation, has been nicknamed Janus, after the two-faced Roman god of transition, although its formal scientific name is ZTF J203349.8+322901.1. It was initially discovered by the Zwicky Transient Facility (ZTF), an instrument that scans the skies every night from Caltech's Palomar Observatory near San Diego.

"The surface of the white dwarf completely changes from one side to the other," said Dr Ilaria Caiazzo, an astrophysicist at Caltech who led the work. "When I show the observations to people, they are blown away." Caiazzo was searching for white dwarfs and one candidate star stood out due to its rapid changes in brightness. Further observations revealed that Janus was rotating on its axis every 15 minutes. Spectrometry measurements, which give the chemical fingerprints of a star, showed that one side of the object contained almost entirely hydrogen and the other almost entirely helium. If seen up close, both sides of the star would be bluish in colour and have a similar brightness, but the helium side would have a grainy, patchwork appearance like that of our own sun, while the hydrogen side would appear smooth. The findings are published in the journal Nature.
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Two-Faced Star With Helium and Hydrogen Sides Baffles Astronomers More

Two-Faced Star With Helium and Hydrogen Sides Baffles Astronomers

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  • i think they better wait for other telescopes to inspect this star before they come to this conclusion
    • Why? It is common that 1 result does not make something generally accepted in science. Other astronomers will do their own study to confirm/dispute this result; however, how would other astronomers know about this result before it was published?
    • Did you think this through? Probably not.

      They quote a rotation period for the star of 15 minutes. So, at the minimum they need to have read the target's spectrum twice on the H-rich side and twice on the He-rich side. Minimum 4 observations.

      But, to have high confidence that there is a "H-rich" side versus a "He-rich side", they're going to need ... at least 6 measurements at different phases of the target. So that's a minimum of an hours worth of observations, in addition to the 4 above.

      Actually, since a

  • From the Fucking Abstract: (Score:2, Informative)

    by Anonymous Coward
    "This peculiar nature is probably caused by the presence of a small magnetic field, which creates an inhomogeneity in temperature, pressure or mixing strength over the surface." "Several mechanisms compete with gravitational settling to change a white dwarf’s surface composition as it cools, and the fraction of white dwarfs with helium atmospheres is known to increase by a factor of about 2.5 below a temperature of about 30,000kelvin."

    • Is that just jibber-jabber distracting from the clear observation that things are not mixing according to the rules of Thermodynamics?

      • Re:From the Fucking Abstract: (Score:4, Funny)

        by DrMrLordX ( 559371 ) on Friday July 21, 2023 @05:06AM (#63703862)

        Mr. T says, cut your jibber jabber, or he'll walla walla bing bang you!

      • Does thermodynamics guarantees uniformity in the short term?

        In the absence of other forces we would expect diffusion and bulk mixing to result in a uniformly stratified star. But there could be other forces acting on this star. The original article suggests magnetic fields could affect stratification, and there's also the possibility of a near (in astronomical terms) pass from another massive object introducing asymmetry.

        The real takeaway from this article is that it's a slow news week, so they've had to do

      • Re:From the Fucking Abstract: (Score:4, Insightful)

        by dbialac ( 320955 ) on Friday July 21, 2023 @07:45AM (#63704138)
        We have planets with hexagons at the poles. It seems the laws of thermodynamics aren't so uniform.

        • Are the laws of thermodynamics uniform and unequivocal when it comes to political justification for austerity? Yet the application of those same laws to stars yields 'not so uniform' characteristics, undermining the certainty and confidence with which politicians state that "there is no money left", for example?

        • We have planets with hexagons at the poles. It seems the laws of thermodynamics aren't so uniform.

          Well... they are uniform. We just do not have the imagination to cover all of the possibilities. Any resemblance to incoherence is a perception issue, not a 'law' issue. Same with 'gravity'. There is no Dark Matter or Dark Energy. There is simply a lack of perception and understanding from a limited perspective.

      • The laws of thermodynamics tell you what the equilibrium state of the system would be.

        The last time I looked, the average temperature between a ~1 solar mass white dwarf core at {however many} GK, the WD's surface at 30-odd kK and a universe of material at about 2.8 K ... was pretty close to 3 K.

        The system under description is far from equilibrium. The laws of thermodynamics will tell you which way the system will evolve, and to a degree how fast it will do that evolution. But they don't make such a syste

        • "What would be impossible would be for the WD core to get hotter by heat flowing into it from the rest of the universe."

          Like a car with the windows rolled up?

    • The abstract also says:

      ZTFJ203349.8+322901.1 might be the most extreme member of a class of magnetic, transitioning white dwarfs—together with GD323 (ref. 12), a white dwarf that shows similar but much more subtle variations.

      I have a rule that when the headline claims scientists are 'baffled' or something similar, the details in the source material will indicate the opposite. But as always, a headline 'astronomers have some good theories for this object which is much like other known objects but not exactly' doesn't sell any ad slots.

  • This surprises me for a different reason. (Score:4, Interesting)

    by Anonymous Coward on Friday July 21, 2023 @03:34AM (#63703756)

    A lot of people have difficulty grasping how big the visible universe is. What's actually surprising is that we don't see things that seem improbable more often. Perhaps as we get more telescopes in space, we'll find more of them.

    • FWIW, the chance of seeing something improbable increases in proportion to the number of eyes looking, but is not affected the number of objects that could be looked at (for large numbers).

      • The geometry of the observed universe is flat, which implies an infinite universe. Therefore, from what we know now, it can be said that there are no impossible things at all. Events with even the tiniest chance to occur have occurred or will occur.

        Only impossibility is a random universe though, because certain important constants do appear to be universal. It is all based on the same fundamental principles.

        • Re: (Score:2)

          by yo303 ( 558777 )

          That's... not a thing. There's a finite mass in the observable universe. If there were unreachable parts of all of reality, that doesn't matter to us. Every possible thing will not happen before the heat death of the universe.

          • There are unreachable parts: the rest of the likely infinite universe. There can as well be a myriad of civilizations out there we have no way of contacting ever, because the expansion of the universe makes it impossible.

            I admit this is closer to philosophical thinking, but after all, there is also logic in the idea of how the universe is a large sea of probabilities where its parts interact with each other. It is true time is finite for that although there is very much of that left too.

        • . Events with even the tiniest chance to occur have occurred or will occur.

          But that says noting about events with no chance to occur.
          Which is what impossible means.

    • Re:This surprises me for a different reason. (Score:5, Interesting)

      by Viol8 ( 599362 ) on Friday July 21, 2023 @05:42AM (#63703922) Homepage

      It wouldn't surprise me of some alien astronomers were one day examining the spectrograph of earth and wibbled through their mouth-eye stalks "Free oxygen in an atmosphere?? How the hell does happen??" followed by lots of their equivalents of white papers positiing wierd geology or some impact etc.

      • Yeah, and another alien wibbling back that oxygen is dangerously reactive and there's no possibility of life on a world without liquid ammonia.

      • To be fair, their incredulousness is justified: it seems to have resulted in a nearly-absolute shitshow here.

      • "Free oxygen in an atmosphere?? How the hell does happen??"

        I doubt alien astronomers are baffled by this unless their society never developed chemistry. Even in our limited knowledge of the universe, there are already a myriad of plausible explanations have if we detect this in another planet. One possibility is a complex ecosystem with life. But there are non-biological possibilities too.

        • its not so much the presence of Oxygen but the concentrations that would be the issue.

          As you point out there are numerous non-biological chemical reactions that can cause detectable levels of free Oxygen in an atmosphere, but other non-biological chemical reactions would capture it and prevent the over all concentrations in the atmosphere from being significant to any degree. Concentrations of .1 to 5% wouldn't raise an eye flap as they would be easy to explain.

          What would make Earth stand out is the ~23% f

          • The one thing is that scientists are not "baffled" if they find a planet with 5% or 20%. The reality is that scientists are not definitively sure about the explanation of a fact not that they are "baffled".

    • A lot of people have difficulty grasping how big the visible universe is.

      If people were standing on the shore of the ocean and a tsunami 2 miles high and a thousand miles long formed, all of the people present would have a hard time conceptualizing exactly how large that tsunami is despite witnessing it in person. It would be the most terrifying thing ever witnessed. And yet, compared to the size of the Earth, it is not really a very large thing at all. But even worse, the Planet Earth, the entire planet, is barely comparable to a mote of dust... and you think anyone can truly u

  • Broken link (Score:3)

    by Pieroxy ( 222434 ) on Friday July 21, 2023 @04:42AM (#63703832) Homepage

    The first link of the story points to nothing. Can you fix it ?

  • Is it possible it's just two stars that combined?
    • Either that, or a really heavy and small companion that heavily influences the visible star by its gravity.

    • Re: (Score:2)

      by dgatwood ( 11270 )

      Is it possible it's just two stars that combined?

      Or that it is farther away than they thought, and it is two stars that are just really close to each other?

      • How would that scenario explain the alternating appearance of one star then another (your hypothesis) at regular (15 minute) intervals, which observation this paper's authors interpret as signs of rotation of an inhomogeneous surface about an axis at a high angle to the line of sight?

        • Re: (Score:2)

          by dgatwood ( 11270 )

          Binary star system in a fast rotation?

          • Then you'd see the maximum brightness separated by two different depths of minimæ. Interpretation of the light curves of eclipsing binaries is a standard part of even fairly basic astronomy courses. Such a basic part that it wasn't even considered because the light curve they obtained (by many hours of observation at several observatories over several visits) was clearly not one of an eclipsing binary. If you READ THE FRIENDLY PAPER (link given upthread) you'll find the light curve at 5 different

            • Re: (Score:2)

              by dgatwood ( 11270 )

              If your two binary components have an overlapping or contacting atmosphere, it looks somewhat more like a sinusoid, but alternating minima are of different depths, revealing the more complex structure than from a single rotating body.

              Thanks. I didn't read the actual article. Just asking questions out of curiosity, because I don't have any real background in this, and I'm curious. :-)

              If one star were on the main sequence and the other star weren't, and both had about the same size and intensity (not 100% sure that's possible), and they were partially overlapping, it seems like you wouldn't have different minima, would you?

              I also wonder if a large mass (e.g. a comet or asteroid) moving at sufficiently high speed could pass through the c

              • If one star were on the main sequence and the other star weren't, and both had about the same size and intensity (not 100% sure that's possible), and they were partially overlapping, it seems like you wouldn't have different minima, would you?

                It's hard to get to that situation. I think it's impossible to do that without having a substantially different colour to your two bodies.

                FTFA (which you didn't read), you'll see that once they'd identified the phase of the light curve, they took multiple spectra thro

                • Damn. Slashcode can't even handle standard HTML entities like & angst ; - the Angstrom symbol (also known as Å & Aring; - the ringed-capital A character). Is it ... 26 years we've been complaining about this? 27?
    • Conservation of angular momentum would make that really hard without a considerable degree of mixing..

      Stir a cup of black coffee. Stir a cup of milk (or cream, if that's your poison). Pour one into the other, as fast or as slow as you like. Do you get mixing.

      The resultant body has a rotation period of 15 minutes. How are you going to get that without the pre-merger (your hypothesis) system having significant rotation, either of it's components (compared to each other) or each individual component itself r

  • Clearly it is inhabited by politicians.

    • Re: (Score:2)

      by sjames ( 1099 )

      Impossible. helium and hydrogen are both valuable. Politicians never produce anything of value.

  • (reads title)
    please, tell me they didn't call it Janus... please...
    (reads abstract)
    DOH! :-)

    • What's the problem with calling it Janus? I can't think of any mythological characters that fit the characters better. Nor, for that matter, any "popular culture" figures either.

      You do better. What's your suggestion?

  • ...this was part of a SETI project. The alien in charge said: "Okay. We just turned a star into a fucking strobe light. If there's anyone out there, they'll definitely see it."

    And now the signal has reached us. Unfortunately, that alien has been dead for a little over nine hundred years.

  • Just a couple of days ago [slashdot.org] we had a report of a 21min period pulsar (with an 18 min pulsar discussed in The Friendly Paper). And here's another 15 min compact body. If I didn't know better, I'd think that some milli- to micro- Hz instruments had started to pump data out of it's observation-to-publication pipeline. But that previous one originated in the Murchison Widefield Array, while this one sprang from ZTF observations, backed up by subsequent observations on two other, different, telescopes at different

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