Astronomers detect diamond dust shimmering around distant stars

From Greenbank Observatory

Nanoscale gemstones source of mysterious cosmic microwave light

This is an artist impression of nanoscale diamonds surrounding a young star in the Milky Way. Recent GBT and ATCA observations have identified the telltale radio signal of diamond dust around 3 such stars, suggesting they are a source of the so-called anomalous microwave emission. CREDIT S. Dagnello, NRAO/AUI/NSF

For decades, astronomers have puzzled over the exact source of a peculiar type of faint microwave light emanating from a number of regions across the Milky Way. Known as anomalous microwave emission (AME), this light comes from energy released by rapidly spinning nanoparticles – bits of matter so small that they defy detection by ordinary microscopes. (The period on an average printed page is approximately 500,000 nanometers across.)

“Though we know that some type of particle is responsible for this microwave light, its precise source has been a puzzle since it was first detected nearly 20 years ago,” said Jane Greaves, an astronomer at Cardiff University in Wales and lead author on a paper announcing this result in Nature Astronomy.

Until now, the most likely culprit for this microwave emission was thought to be a class of organic molecules known as polycyclic aromatic hydrocarbons (PAHs) – carbon-based molecules found throughout interstellar space and recognized by the distinct, yet faint infrared (IR) light they emit. Nanodiamonds — particularly hydrogenated nanodiamonds, those bristling with hydrogen-bearing molecules on their surfaces — also naturally emit in the infrared portion of the spectrum, but at a different wavelength.

A series of observations with the National Science Foundation’s Green Bank Telescope (GBT) in West Virginia and the Australia Telescope Compact Array (ATCA) has — for the first time — homed in on three clear sources of AME light, the protoplanetary disks surrounding the young stars known as V892 Tau, HD 97048, and MWC 297. The GBT observed V892 Tau and the ATCA observed the other two systems.

“This is the first clear detection of anomalous microwave emission coming from protoplanetary disks,” said David Frayer a coauthor on the paper and astronomer with the Green Bank Observatory.

The astronomers also note that the infrared light coming from these systems matches the unique signature of nanodiamonds. Other protoplanetary disks throughout the Milky Way, however, have the clear infrared signature of PAHs yet show no signs of the AME light.

This strongly suggests that PAHs are not the mysterious source of anomalous microwave radiation, as astronomers once thought. Rather, hydrogenated nanodiamonds, which form naturally within protoplanetary disks and are found in meteorites on Earth, are the most likely source of AME light in our galaxy.

“In a Sherlock Holmes-like method of eliminating all other causes, we can confidently say the best candidate capable of producing this microwave glow is the presence of nanodiamonds around these newly formed stars,” said Greaves. Based on their observations, the astronomers estimate that up to 1-2 percent of the total carbon in these protoplanetary disks has gone into forming nanodiamonds.

Evidence for nanodiamonds in protoplanetary disks has grown over the past several decades. This is, however, the first clear connection between nanodiamonds and AME in any setting.

Statistical models also strongly support the premise that nanodiamonds are abundant around infant stars and are responsible for the anomalous microwave emission found there. “There is a one in 10,000 chance, or less, that this connection is due to chance,” said Frayer.

For their research, the astronomers used the GBT and ATCA to survey 14 young stars across the Milky Way for hints of anomalous microwave emission. AME was clearly seen in 3 of the 14 stars, which are also the only 3 stars of the 14 that show the IR spectral signature of hydrogenated nanodiamonds. “In fact, these are so rare,” notes Greaves, “no other young stars have the confirmed infrared imprint.”

This detection has interesting implications for the study of cosmology and the search for evidence that our universe began with a period of inflation. If immediately after the Big Bang, our universe grew at a pace that vastly outstripped the speed of light, a trace of that period of inflation should be seen in a peculiar polarization of the cosmic microwave background. Though this signature of polarization has yet to be conclusively detected, the work by Greaves and her colleagues offers some hope that it could be.

“This is good news for those who study polarization of the cosmic microwave background, since the signal from spinning nanodiamonds would be weakly polarized at best,” said Brian Mason, an astronomer at the National Radio Astronomy Observatory and coauthor on the paper. “This means that astronomers can now make better models of the foreground microwave light from our galaxy, which must be removed to study the distant afterglow of the Big Bang.”

Nanodiamonds likely form out of a superheated vapor of carbon atoms in highly energized star-forming regions. This is not unlike industrial methods of creating nanodiamonds on Earth.

In astronomy, nanodiamonds are special in that their structure produces what is known as a “dipole moment” – an arrangement of atoms that allows them to emit electromagnetic radiation when they spin. Because these particles are so small – smaller than normal dust particles in a protoplanetary disk — they are able to spin exceptionally fast, emitting radiation in the microwave range rather than in the meter-wavelength range, where galactic and intergalactic radiation would probably drown it out.

“This is a cool and unexpected resolution to the puzzle of anomalous microwave radiation,” concluded Greaves. “It’s even more interesting that it was obtained by looking at protoplanetary disks, shedding light on the chemical features of early solar systems, including our own.”

“It is an exciting result,” concluded co-author Anna Scaife from Manchester University. “It’s not often you find yourself putting new words to famous tunes, but ‘AME in the Sky with Diamonds’ seems a thoughtful way of summarizing our research.”

Future centimeter-wave instruments, like the planned Band 1 receivers on ALMA and the Next Generation Very Large Array, will be able to study this phenomenon in much greater detail. Now that there is a physical model and, for the first time, a clear spectral signature, astronomers expect our understanding will improve quickly.

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38 thoughts on “Astronomers detect diamond dust shimmering around distant stars

    • HD 97048 is an A0pshe spectral class star at 160 ± 20 pc
      MWC 297 is a B1.5V spectral class star at 250 ± 50 pc
      V892 Tau is an A0 spectral class star at about 140 pc.

      If you want the distances in light-years, then one parsec is equal to about 3.26 light-years.

      Jim

  1. What? No reference to the vampires in ‘Twilight’ covered with sparkly diamond dust stuff?

    And still no answers on the SETI wave length. (Sigh) Maybe… some day…

    • When you stop to consider that the rates of increase of disease and cancer appear to parallel the increased use of the radio spectrum, it would seem almost logical to assume any advanced civilization doesn’t rely on utilizing the radio spectrum for anything, thus any “signal” on the SETI wave length would probably be from a dead or dying civilization.

      • Life spans also increase, that’s probably why the seeming increase in certain diseases and cancer. People live long enough to contract said diseases.

      • Even the notoriously hypochondriac European Union hasn’t managed to find evidence that RF energy has any link to cancer or any disease. Only heating effects and maybe neurological effects.

  2. Is it nanodiamonds in protoplanetary disks from interstellar regions, or from ejected from a supernova? Would this spectral region be observable near the Crab – in other words where is the diamond coming from? Reheated dust near a new solar system or from the shock of a supernova? If shock, then the nanodiamonds should be diffused.
    Just as Sn1987a appeared, http://articles.latimes.com/1987-03-12/news/mn-9346_1_earth-from-exploding-stars
    “supernova 1987A could have produced about 1/1000th of a solar mass of diamond dust”. Such diamond should be infused with “strange” Xenon – not sure how observable there, but found in meteorites, and strangely in solar flares.

  3. I speculate that the speed of light through diamond is around 20% slower than in a vacuum. Given sufficient particles along a light-path, could this have a measurable effect on ‘red-shifting’?

  4. Re: “In a Sherlock Holmes-like method of eliminating all other causes, we can confidently say the best candidate capable of producing this microwave glow is the presence of nanodiamonds around these newly formed stars”

    It’s unfortunate that such a claim goes completely unchallenged, because here on Earth, we generate microwaves with electric currents.

    Anthony L. Peratt, Physics of the Plasma Universe, Second Edition, 2015, p.33-34. https://books.google.com/books?id=wt2CBAAAQBAJ&pg=PA34

    “High-power microwave generation on earth belongs exclusively to devices using relativistic electron beams … A relativistic electron beam that does not produce microwave radiation is unknown. These same basic mechanisms are likely to have their natural analogs in cosmic plasmas.”

  5. Gotta love interpretation of results. I have my doubts on this. Not enough evidence imo.

    But the science media would love the idea of diamonds in such abundance

    The actual reality is, this is inconclusive, a guess, a pretty sparkly guess, but a guess nonetheless

    • How fast do diamonds have to spin to produce “microwave light”. (what is microwave light? The term microwave usually applies to radio waves in the 1-30 GHz band).

      It seams that anything is possible if the name includes ‘nano’.

      • The broadest definition is EM radiation with wavelengths between one meter to one millimeter (frequencies from ~300 MHz to 300 GHz). The narrower definition of one to 100 GHz (wavelengths between 30 cm and 3 mm) applies in radio engineering.

        (The wavelength associated with a frequency of one MHz is actually 299.792458 meters.)

        You’re right that microwaves are generally considered in the radiowave range rather than “light”.

  6. From my point of view and my understanding, even when I can not rely or refer to the proper paper, but mainly considering this in the aspect of this blog post and the info here, I think this seems very interesting and mind inspiring.

    But still only very few comments here.

    As far as I can tell this seems to be an Anthony post.

    In the aspect of trying to pinch it a bit further…As far as I can tell at this point, this statement, supposedly from Anthony seems wrong, as per below:
    ——–
    “This strongly suggests that PAHs are not the mysterious source of anomalous microwave radiation, as astronomers once thought. Rather, hydrogenated nanodiamonds, which form naturally within protoplanetary disks and are found in meteorites on Earth, are the most likely source of AME light in our galaxy.”
    ———
    This, as far I can understand does not reasonably compute with what point it out and the actual main evidence offered, as per the main position of the paper in question, as served here.

    The answer to my earlier question by Jim, clearly puts the location of the main evidenced source far, far too far out of the Milky way Galaxy,which brings me back to this consideration, of who could be wrong, Jim or Anthony….where one thing impossible is the consideration of both being right….

    Anyway, I am not trying to upset or whatever, I am just trying a say that this paper maybe pointing to something new in a new angle, and maybe have some more value than when seen superficially.

    Simple question again:

    How many AME signal sources can and are actually identified within our galaxy????

    I will very much appreciate if some one can specifically answer this question!

    cheers

      • Felix
        —–
        This sources, are well far far, too far away, out of our galaxy, according to the Jim answer above to my question also above. Even when considering the clause “across the Milky Way”

        That clause does not by default means “within the Milky Way” or within our galaxy.

        That is what the point, or the main point in my comment that you replied to.

        This kind of argument, as forwarded in this blog post, relies a lot in a paper that as per my assumption, makes a case where main “evidence” consist of three sources well far away from the edge of our galaxy, where the clause of “across” the Milky Way does not and can not change this, but only may lead to self misleading conclusion….that what I think the case.

        But any how I must accept that all this in my part, is very much standing in a superficial info.

        I really do not know if there is any real or proper AME signal within the Milky Way, our galaxy, that is why I questioning above about.

        cheers

    • >>
      The answer to my earlier question by Jim, clearly puts the location of the main evidenced source far, far too far out of the Milky way Galaxy . . . .
      <<

      The diameter of the Milky Way Galaxy is estimated at 31-55 kpc (that’s kiloparsecs). The distance to the galactic center is around 8.7 kpc (or 8,700 parsecs). So a measly 250 parsecs is nearby by comparison and well within the galaxy.

      Jim

      • Thanks again Jim.
        Completely my fault.
        Must have read the distances you gave in kpc.
        Really sorry. Apology to Anthony and Felix also.

        Thanks again Jim for the clarification and the correction, and your time.
        : ) Very helpful.
        cheers

      • Now they are saying that the Milky Way Galaxy has a radius of 31 kpc or 100,000 light-years.

        Jim

        • Does that mean now the distance of Earth from the center of Milky Way has gone up by a X2?
          Or am I getting this wrong, again!

          • From the article, the mass hasn’t changed–the outer stars extend farther than previously thought. The distance to the center should be the same.

            Jim

          • Sorry Jim, but not possible, as far as I can tell, if I am not wrong again, if ratios not maintained, then mass does not really matter.
            The distance of Earth to the center of our galaxy really does matter.

            The point still stands as per the ratio and its meaning….does that distance, or has that distance to be considered as per X2 or not!?

            Simple, what is, when the Earth distance from the Milky Way center considered, is it X2 or not, as per consideration of ratio maintained!????

            What is that gives or not!

            The error tolerance, as far as I can tell, will be ~ the same as the actual distance, contemplated here, where the distance ~28k light-years, with an error tolerance contemplated at ~25k light-years.

            Can you spot the problem here, if the distance been considered as in the point of it got to be or it should be maintained as the same?!

            I am not quite certain of the clarity or the proper explaining from my position being good enough or not, only trying my best.

            My wild guess at this point stands as per, 40K X correction applied to the size of the center of our galaxy only, without regard or care for to the rest…very arbitrary.

            But hey I could be horribly wrong in this one to…..

            cheers

          • First off, I don’t know where you’re getting this X2 stuff. Admittedly, I’ve only read press releases, but nothing I’ve read said they are changing the methods of measuring distances. What they have done is reclassify stars from Halo stars to Disk stars. They did that solely from spectral analysis. This has the effect of extending the disk out twice as far. The old methods of measuring distance still hold.

            Jim

          • Thanks again Jim

            Extending of the disc twice as far (X2) should raise the question if the distance of Earth from the center of the Milky Way extends too, will that be by X2, twice as far, or not? If it extends at all!

            I am not saying or claiming that there must be or must have being a change of the distance measurement method……I have not even read the press releases 🙂
            Just trying a see what could this GP extending at twice the previous (X2)
            could mean, especially for the distance of Earth from the G center.!

            Thanks Jim, very kind of you.

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