When A Standard Candle Flickers


Roll over, Edwin Hubble. For many decades astronomers have relied upon the “standard candle” to express the brightness of a Cepheid variable star, thereby establishing a distance. But not anymore… Now there’s evidence that Cepheid variables can shrink in mass and that bit of information changes the whole picture. The findings, made with NASA’s Spitzer Space Telescope, will help astronomers make even more precise measurements of the size, age and expansion rate of our Universe. Strap on your cosmic seat belt and read on…

According to today’s American Astronomical Society Press Release, standard candles are astronomical objects that make up the rungs of the so-called cosmic distance ladder, a tool for measuring the distances to farther and farther galaxies. The ladder’s first rung consists of pulsating stars called Cepheid variables, or Cepheids for short. Measurements of the distances to these stars from Earth are critical in making precise measurements of even more distant objects. Each rung on the ladder depends on the previous one, so without accurate Cepheid measurements, the whole cosmic distance ladder would come unhinged. Now, new observations from Spitzer show that keeping this ladder secure requires even more careful attention to Cepheids. The telescope’s infrared observations of one particular Cepheid provide the first direct evidence that these stars can lose mass—or essentially shrink. This could affect measurements of their distances.

“We have shown that these particular standard candles are slowly consumed by their wind,” said Massimo Marengo of Iowa State University, Ames, Iowa, lead author of a recent study on the discovery appearing in the Astronomical Journal. “When using Cepheids as standard candles, we must be extra careful because, much like actual candles, they are consumed as they burn.”

The star in the study is Delta Cephei, which is the namesake for the entire class of Cepheids. It was discovered in 1784 in the
constellation Cepheus, or the King. Intermediate-mass stars can become Cepheids when they are middle-aged, pulsing with a regular beat that is related to how bright they are. This unique trait allows astronomers to take the pulse of a Cepheid and figure out how bright it is intrinsically—or how bright it would be if you were right next to it. By measuring how bright the star appears in the sky, and comparing this to its intrinsic brightness, it can then be determined how far away it must be. This calculation was famously performed by astronomer Edwin Hubble in 1924, leading to the revelation that our galaxy is just one of many in a vast cosmic sea. Cepheids also helped in the discovery that our universe is expanding and galaxies are drifting apart.

Cepheids have since become reliable rungs on the cosmic distance ladder, but mysteries about these standard candles remain. One question has been whether or not they lose mass. Winds from a Cepheid star could blow off significant amounts of gas and dust, forming a dusty cocoon around the star that would affect how bright it appears. This, in turn, would affect calculations of its distance. Previous research had hinted at such mass loss, but more direct evidence was needed. Marengo and his colleague used Spitzer’s infrared vision to study the dust around Delta Cephei. This particular star is racing along through space at high speeds, pushing interstellar gas and dust into a bow shock up ahead. Luckily for the scientists, a nearby companion star happens to be lighting the area, making the bow shock easier to see. By studying the size and structure of the shock, the team was able to show that a strong, massive wind from the star is pushing against the interstellar gas and dust. In addition, the team calculated that this wind is up to one million times stronger than the wind blown by our Sun. This proves that Delta Cephei is shrinking slightly.

Follow-up observations of other Cepheids conducted by the same team using Spitzer have shown that other Cepheids, up to 25 percent observed, are also losing mass. “Everything crumbles in cosmology studies if you don’t start up with the most precise measurements of Cepheids possible,” said Pauline Barmby of the University of Western Ontario, Canada, lead author of the follow-up Cepheid study published online Jan. 6 in the Astronomical Journal. “This discovery will allow us to better understand these stars, and use them as ever more precise distance indicators.”

Like Pluto, this means we will end up having to re-write our astronomy books… But it’s a “birth day” candle we’re ready to blow out!

Original Source: American Astronomical Society Press Release – Photo Credit: NASA

26 Replies to “When A Standard Candle Flickers”

  1. I’m sure Edwin would be fascinated! What does the red color in the image on the left represent? Over lain deep IR data in a sectional view? Or is that perhaps the actual shape of the ejected dust and gas (accretion disk?) surrounding Delta Cephei?

  2. Good article !
    Mainstream Astrophysics has been far too certain and for much too long, that its interpretation is correct about what it is seeing. Those overly confident assumptions are coming home to roost.
    When their likewise assumptions about Redshift crumble and fall, the dam will break and the revolution will begin in full sway !

    1. Actually, the article does absolutely nothing to even give the slightest suspicion that the Cepheid P-L relation may be off except for some poorly considered hype in the opening that’s not supported by the study or the rest of the article.

      Regardless of whether mass is lost or not, the relationship is firmly established with known errors that are factored into all distance determinations and carried throughout the cosmological distance ladder. Indeed, entire ladders have been constructed entirely removing Cepheids, and the Hubble constant still comes out to be the same (within the small errors).

      Similarly, the redshift interpretation has been thoroughly tested and supported. No other redshifting effects other than Doppler can account for the shift, and the effect is exceptionally well established with overlapping calibrations for confirmation.

      Keep dreaming.

    2. Oh please.

      Let’s see.

      How many Cepheids have we observed to calculate the period-luminosity relationship? One, two, thousand , ten-thousand?

      Also what kind of Cepheids are you talking about. There are several classes of them, you know.

      In the end it is all basic science, and a relationship that has been empirically determined. Not all astrophysics is theoretical.

      If you bothered to learn something about basic stellar evolution you might not appear so mind-numbingly stupid.

      All PC/EU is pseudoscience*, just like reading chicken entrails or reading tarot cards. You might as well be playing the children’s game, pin the tail on the jackass!

      *The only revolution that is come is where pseudoscience is required to submit some kind of prove before even being allowed to speak — not because they think they have some mythical right of freedom of speech, thinking they can say any nonsense they like.

      1. No-one else has brought up Plasma Cosmology (PC) here, but since you mention it, Plasma Cosmology concepts are fully peer-reviewed and aspects form the foundation of modern astrophysics. See for example:
        Alfven, Hannes, “Model of the plasma universe” (1986) IEEE Transactions on Plasma Science (ISSN 0093-3813), vol. PS-14, Dec. 1986, p. 629-638 (abstract).

        Please provide just one peer-reviewed citation to support your pseudoscience claim, or aren’t your opinions supported by science?

      2. Oh, yeah, 1986. A great year. I was been born back then. That’s a quarter of a century ago.

        If you’re interested what we didn’t have in that year: The HST, COBE, WMAP, PLANCK, SWIFT, CGRO, FERMI, etc etc.

        So, since 1986 a lot of research has been done. But no new paper on PC since then? I think, there were at least a few in the 90ies, but nothing since 2000. Why not, I wonder. Could it be due to the little fact that PC cannot reproduce the data?

      3. Oh please.
        lars is a follower of the PC/EU doctrine. One of the aims of PC/EU is to discredit the current astronomical theories and supplant it with its nonsense. It is pseudoscience and there is not one shred of observational evidence to support it. It is based on the grand delusion of individuals who have the pathological desire to fool people that it is mainstream science. Even your so fixated on the delusion you can no longer differentiate fact from fantasy.

        Oh and Alfven’s paper is clear an IEEE paper, it is not an ASTROPHYSICAL PAPER, now is it. Why is it remained an IEEE paper, because it was totally rejected by the astrophysical community, which you guys seem to think means there is some kind of conspiracy plot. His nonsense has been rejected as both implausible and without any observational data to support it.

        Yeah it might have ben peer reviewed, but you conveniently forgot to mention that it was not by astrophysicists by unrelated wannabe electricians / electrical engineers. You might as well quote a peer-reviewed gynaecologist paper on astrophysics! Really, how stupid are you?


      4. Sigh, yet more insults. I have no interest in what you think are lars’ motives, I criticised only your statement on PC. I assume this is because you have no peer-reviewed citations supporting your personal opinion that PC is pseudoscience, or was totally rejected. Back up your statement with some published science.

        PC, may be wrong, and there may be a shortage of articles because of poor data fitting. But it could also be because it has been ignored, and some of the authors are now dead, or retired.

        Plasma Cosmology papers have appeared in many journals, including the following selection:

        *The Proceedings of the Second IEEE International Workshop on Plasma Astrophysics and Cosmology, appearing in Astrophysics and Space Science 227 (1995)

        *Alfven, H., “The plasma universe”, Physics Today, vol. 39, Sept. 1986, p. 22-27.(refereed, but no academic)

        *Alfven, Hannes, “Plasma universe”, International Solar-Terrestrial Physics Symposium, 6th, Toulouse, France, June 30-July 5, 1986) in Physica Scripta, vol. T18, 1987, p. 20-28.

        *Fälthammar, Carl-Gunne, “Magnetosphere-ionosphere interactions —near-Earth manifestations of the plasma Universe”, Astrophysics and Space Science, Volume 144, Issue 1-2, pp. 105-133 (1988)

        *Alfven, Hannes, “Cosmology in the plasma universe”, Laser and Particle Beams, vol. 6, Aug. 1988, p. 389-398.

      5. “PC, may be wrong…”

        Got it in one. It is a fantasy propagated by those who should know better…

      6. “I assume this is because you have no peer-reviewed citations supporting your personal opinion that PC is pseudoscience…”

        I’d asume this is a joke or something like that….

        Now let’s get this right. You want a scientific peer-reviewed citation, on my opinion mind you, about a subject that is already established as a pseudoscience? Isn’t that like asking you want a scientific evaluation on something like the tooth fairy or astrology, which for all intents and purposes us a made up fable that has absolutely nothing to do with definition of science. Yet at the same time, on the assumption that it is an presumed opinion (whether is or not is irrelevant) that you want that fantasy peer reviewed?

        Wh? Who is their right mind would peer review a pseudoscience, let alone pseudoscientific paper? (and you do honestly claim to has a degree in chemistry!) … and I though lars and Muppet were nuts!

        As for the list of silly papers, not one of them is on plasma cosmology! [or even “electric universe”! [I.e PC/EU.]
        I starting to really wonder if you actually know the difference between plasma physics and plasma cosmology?

        The only silly fools to believe this rubbish was in 1986, and the last thing published as an astrophysical subject was Peratt in Sky and Telescope in 1992! Astronomers and astrophysicists laughed so much, the whole ridiculous concept was thrown ceremoniously into the trash can! Apart from a handful of deluded crackpots with a their crazy agenda of reviving the nonsensical ideas, it would have died a merciful death!

        As for “PC, may be wrong, and there may be a shortage of articles because of poor data fitting.” That is really even funnier. The truth is THERE IS NO EVIDENCE TO SUPPORT IT Clearly you have to have the data first, before you can fit it!

        Sorry, I just can’t type anymore… My sides are about to burst from laughing so much! Thank you kindly for the huge giggle!

        (Please don’t respond, I just could face anymore hilarity for a few days! It could kill me!)

    3. I think these PC/EU people need to read up on the Dunning-Kruger effect, but I think they’ll regress back into their comfort zone of blissful ignorance.

  3. @Aqua:
    “In this image, infrared light captured by the infrared array camera is blue and blue-green (3.6- and 4.5-micron light is blue and 8.0-micron light is blue-green). Infrared light captured by the multiband imaging photometer is colored green and red (24-micron light is green and 70-micron light is red). ”

    So it’s a Composite image of two different instruments onboard Spitzer.

    @Tammy Plotner:
    I have one ‘minor’ niggle.
    This finding was presented Massimo Marengo of Iowa State University and was titled “The Delta Cephei Infrared Nebula” .
    I’m mentioning because “When A Standard Candle Flickers” is the title of another presentation by Colleen Marshall of NASA Marshall SFC, regarding the Crab Nebula and Gamma Ray Flares – presumably in the context of the use of the Crab Nebula for the calibration of X-ray telescopes (http://arxiv.org/abs/1010.2679).

    Both of these papers were presented at the 217th AAS meeting in a segment titled ‘Not so standard candles.

    I’ve noticed that a lot of the press regarding this find also seems to be using the “When A Standard Candle Flickers” title.

  4. It helps to understand a little bit what astronomers are doing before you jump to conclusions. When an astronomer looks at a Cepheid variable in another galaxy in order to determine our distance from it, he/she is measuring how fast its brightness varies. Using Leavitt’s law you can then accurately calculate that star’s luminosity. You then measure it’s apparent brightness and you can calculate the distance. The last part of this process is where some uncertainty creeps in. Astronomers do account fo the fact that intervening dust could have an effect on the apparent brightness, but it is a small one. This study demonstrated that about 25 percent of Cepheid variables will have a dust cloud significant enough to effect the apparent brightness. But again the effect is minimal and likely accounted for by the uncertainty already built in to the estimate of the distance. I say likely only since I have yet to look at the hard numbers, but I think it very unlikely that contraints on the distance estimates will change, and if they do only by a very small amount.

  5. “Alternate Astrophysics has been far too certain and for much too long, that its interpretation is correct about what it is seeing. Those overly confident assumptions are coming home to roost.
    Since their likewise assumptions about Redshift crumble and fall, the pre-cosmology view will continue to whimper and whine!”

    There, fixed that for you!

  6. The article states:
    “Follow-up observations of other Cepheids conducted by the same team using Spitzer have shown that other Cepheids, up to 25 percent observed, are also losing mass.”

    Don’t confuse “up to 25 percent observed, are also losing mass” with “25% mass loss”
    The article does not state how much mass gets lost!

    1. It generally follows Reimer’s Formula, calculated per year as;

      Mass loss (M⊙.yr^.- 1.) = 10^-13 ^#215; L☙ #215; R#9753; / M#9753;
      L☙ = Star’s Luminosity [c, 10,000L&#8857/L],
      R☙= Radius [c. 4 to 10&#8857] and
      M☙= Mass c. [c. 4 to 20 M&#8857]
      (All expressed in Solar Units)

      1. No. Remember this is time dependant. Cepheids only last around 10,000 years or so in their evolution, crossing the instability gap in quick time.
        An analogy is starts spend 90% on the Main Sequence, about 8% as red giants, and less than 2% across the so-called Hertzsprung gap. Cepheids are only a small portion in the instability strip within the Hertzsprung gap.

    2. The original paper, however, does:
      “The mass loss rate is in the range 5×10^-9 to 6×10^-8 Mo/yr”

      1. The constant in the mass loss is known variable and highly uncertain, and can be quite different depending on the literature source. Figures you quote are mostly for red giant stars, I think the mass loss of 10^-13 is nominally for main sequence stars. I.e. The Sun. As Cepheids are closer to main sequence stars, they are not shredding as dramatically as red giants on their asymptotic branch.
        Values of 10^-12 to 10^-10 here are probably a fair assumption.

      2. No, actually, the figure I quote is from “The Delta Cephei Infrared Nebula” (the correct name, as I explained in a post currently awaiting moderation because it has a couple of links in it) by Marengo, Massimo; Evans, N. R.; Barmby, P.; Matthews, L. D.; Bono, G.; Welch, D. L.; Romaniello, M.; Huelsman, D.; Su, K. Y. L.; Fazio, G. G.

        The Abstract for which is currently available on NASA ADS (but not the full text version) the last two sentences of the first paragraph of which state:
        “This discovery is the first direct determination of mass loss from a Cepheid star. The mass loss rate is in the range 5×10^-9 to 6×10^-8 Mo/yr, which has important implications for the still unsolved “Cepheids mass loss discrepancy” and for the cosmic distance scale as calibrated with the Cepheid period-luminosity relation.”

      3. I accept that, … but I did say;

        “The constant in the mass loss is known variable and highly uncertain, and can be quite different depending on the literature source.”

        The object in which the study was done was on Delta Cephei itself, and was based on the 24 and 70 micron emissions. The value quoted is fairly approximate. I.e. “An Infrared Nebula Associated with ? Cephei: Evidence of Mass Loss?” By the same group of people.

        I’d recommend you read the excellent downloadable “summary” paper by Keller;
        Cepheid Mass loss and the Pulsation-Evolutionary Mass Discrepancy (2008)

        This paper says, that theoretically, “The implied total mass loss declines from ~20% at M ~5 Mo and vanishes by M ~14 Mo.
        (I’ve read this elsewhere too, hence my ‘guess’ of 10^-12 to 10^-10. I.e. A mean Cepheid of around 10 solar masses)

        Keller further says; “…Such mass loss is seemingly at odds with empirical estimates of mass-loss rates which show that mass loss increases with stellar luminosity and radius (Reimers 1975; de Jager et al. 1988; Schroeder & Cuntz 2007)

        This is why Keller say; “Mass loss, in an ad hoc manner at least, offers a mechanism to modify the M-L relation by directly reducing the mass of a Cepheid.

        It is interesting that the same value quoted in Marengo et.al. is virtually the same as stated on pg.485 of Keller’s paper.

        Again, my comment is based on the same as Keller’s point;

        To say; “Furthermore, standard mass loss can account for at most a few percent reduction in Cepheid mass and not the 15%Y20% required. Mass loss is usually treated the semiempirical relation of Reimers (1975) ‘‘Reimers’ law.’’ While not providing any physical reasoning on why the mass loss is generated, ‘‘Reimers’ law’’ provides an adequate match to observed mass-loss rates over a broad range of stellar parameters (Schroeder & Cuntz 2007).”

        New observations, like what you quote, show that the real result maybe different.

  7. @HSBC:
    And I accept that (and realized that).

    That as this is the first experimental determination of its kind, its probably going to differ from the literature values up until now (as so often happens).

    Kellers paper certainly looks interesting, I will have to peruse it soon.

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