≡ Menu

Dark Energy: Dimming a Standard Candle?

How light travels through various media can tell us volumes. Take the phenomenon called ‘extinction,’ which describes what happens to light as it encounters dust and gas between the original object and our position on Earth. Studying this effect led to our earliest understanding of interstellar dust as a factor to be taken into account of when discussing the space between the stars. And because we have much to learn about what is in that space, a new observation proves useful indeed, adding to our options for the study of ‘dark energy,’ the mysterious repulsive force that seems to account for the accelerating expansion of the universe.

Examining what they describe as a new form of carbon found within minerals in meteorites, Andrew Steele and Marc Fries (Carnegie Institution) examine the question of how these so-called ‘graphite whiskers’ might affect astronomical observations. The going theory is that the whiskers may have formed near the Sun early in our Solar System’s life, being pushed into interstellar space through the action of the solar wind. Supernovae may also be a factor in their production.

We’re early in the game on this, but a haze of this material would clearly have effects on the way light passes through space. Type 1a supernovae have been considered to be ‘standard candles,’ their brightness offering a useful gauge of their distance. It was observations of particular Type 1a supernovae whose light was believed to be dimmer than it ought to have been at near infrared wavelengths that in the 1990’s helped to shape the accelerated expansion theory.

But if these supernovae are dimmer than expected, accelerated expansion is but one explanation. An alternative in the form of some kind of intervening material has long been suggested as a solution, but evidence for graphite whiskers has never been confirmed until now. Which leads us to Andrew Steele’s interesting comment:

“If graphite whiskers in space are absorbing supernovae’s light, then this could affect measurements of the rate of the universe’s expansion. While we cannot comment further on the effects of whiskers on the dark energy hypothesis it is important to study the characteristics of this form of carbon carefully so we can understand its impact on dark energy models. We’ll then feed this data forward to the upcoming NASA and ESA (European Space Agency) missions that will look for the effects of dark energy.”

The researchers note that graphite whiskers ought to form close to the Sun in the condensation period as protoplanetary disk materials coalesce. The inference, then, is that any young star system may expel such whiskers, accounting for what could be a factor to be reckoned with in near infrared dimming. The paper is Fries and Steele, “Graphite Whiskers in CV3 Meteorites,” Science Express February 28, 2008 (abstract). More in this Carnegie Institution news release.

Comments on this entry are closed.

  • ljk March 1, 2008, 14:08

    WMAP Haze: Directly Observing Dark Matter?

    Authors: Michael McNeil Forbes, Ariel R. Zhitnitsky

    (Submitted on 26 Feb 2008)

    Abstract: In this paper we show that dark matter in the form of dense matter/antimatter nuggets could provide a natural and unified explanation for several distinct bands of diffuse radiation from the core of the galaxy spanning over 13 orders of magnitude in frequency. We fix all of the phenomenological properties of this model by matching to X-ray observations in the keV band, and then calculate the unambiguously predicted thermal emission in the microwave band, at frequencies smaller by 11 orders of magnitude.

    Remarkably, the intensity and spectrum of the emitted thermal radiation are consistent with – and could entirely explain – the so-called “WMAP haze”: a diffuse microwave excess observed from the core of our galaxy. This provides another strong constraint of our proposal, and a remarkable non-trivial validation. If correct, our proposal identifies the nature of the dark matter, explains baryogenesis, and provides a means to directly probe the matter distribution in our Galaxy by analyzing several different types of diffuse emissions.

    Comments: 13 pages, REVTeX4

    Subjects: Astrophysics (astro-ph); High Energy Physics – Phenomenology (hep-ph); Nuclear Theory (nucl-th)

    Report number: NT@UW-08-05

    Cite as: arXiv:0802.3830v1 [astro-ph]

    Submission history

    From: Michael McNeil Forbes [view email]

    [v1] Tue, 26 Feb 2008 16:15:27 GMT (41kb)

    http://arxiv.org/abs/0802.3830

  • dad2059 March 2, 2008, 12:31

    So I take it to mean that the accelerated expansion of the Universe might or might not be as advertised, due to these graphite whiskers blocking, or cutting down significantly infrared radiation from type 1a supernovae?

    Hmmm, it’s good news in a way, it means the Universe might not die a cold, light-less death.

    The bad news is that the dark energy/matter meme that’s been spread for the past ten years could suffer that demise and put alot of astrophysicists out of a job!

    Or tenure at universities anyways.

  • James M. Essig March 3, 2008, 0:35

    Hi Paul;

    This is a very interesting article. If it turns out that dark energy is not the explaination for the observed dimming of the type 1a supernova, but instead interstellar carbon wiskers are, this will obviously negate the need to explain cosmic expansion in terms of dark energy and we can all be a bit more excited because we will have learned something new.

    Whether the universe will one day collapse, is flat and open, is of a open saddle shaped curvature, will one day experience one or more unpredicted quantum mechanical event induced phase changes, is multiply connected etc., there will still be many questions to ask and answer.

    In the event that the universe is closed, how to deal with the Big Crunch will be an issue. Will the information within the Big Crunch be maintained in such a way that the record of our bodies will be preserved so that they can be reconsituted somehow in the future in any cyclical universe? Perhaps the meaning of future will be nonexistent relative to our cycle with respect to socalled future cycles if thermodynamic information is not conserved since space and time are unified under special and general relativity and in a sense so is space-time-mattergy. Without the present space time continuum as a result of complete distruction and thermodynamic information death, the meaning of the future after our universe might not exist or make sense.

    The rebirth of any cyclical universe may have various ramifications some of which have been studied mathematically/theoretically. I have often wondered if this rebirth would be akin to some sort of ressurection espoused by many of the Earth’s religions. One can imagine a cycle of death and rebirth that goes on essentially forever and this idea intriques me although modern cyclical theories suggest that the length of time between sucessive births will change over time due to the laws of information consevaration and thermodynamics.

    A universe that expands forever and goes through an infinite series of phase changes in the depths of physical eternity intrigues me also.

    ljk;

    These matter/antimatter nuggets might make an excellent fuel source to be harnessed by many generation very high gamma factor space arks that could ply the depths of intergalactic space ultimately over cosmic distances.

    dad2059;

    Perhaps these graphite wiskers could be harnessed by interstellar ramjet like craft for continuous propulsion. It would indeed be good news if the universe is not destined to die a cold death. However, even if at first it would appear that the universe would die in such a way, there is always the possibility that some sort of vacuum state phase change could make things interesting again with a new period of inflation and futher symmetry breaking perhaps involving the branching off of the electric and magnetic components of the electromagnetic force. Perhaps these seperated components would have a richness all their own simmilar in complexity to the current electromagnetic force. Or perhaps the strong nuclear force or the weak nuclear force will experience a branching that is distinct or not the same as the symmetry breaking that lead to the seperation of the strong force from the weak and electromagnetic force, and the weak and electromagnetic force from the electroweak unification. Who knows, there even be an ensemble if not infinite sucession of such symmetry breakings in the depths of physical eternity thus leading to great richness within the phenomena, lifeforms, and technologies possible within the universe.

    Thanks;

    Jim

  • Adam March 3, 2008, 2:31

    Hi dad2059

    There’s a lot of work before that outcome obtains. What it does mean is the data will have to be scoured for signs of distortion by intervening graphite whiskers – apparently the suggestion is over 20 years old and was made by the Steady State crew originally. Not a lot of direct evidence back in 1986, but the new physical evidence isn’t a slam dunk yet either.

  • dad2059 March 3, 2008, 8:35

    Thanks for the responses Adam and Jim. Yes indeed, much more info is needed before the forever accelerating Universe/dark matter theory is put to bed. I for one welcome it.

    I always found the cold death Universe depressing. It reminds me of dying a slow, freezing death in the Antarctic, miles away from anyone.

  • Administrator March 3, 2008, 10:41

    I’ll concur with Adam that the graphite whisker hypothesis is a long way from being proven, just as the existence of dark energy is still on the table. We’re working with observational data that don’t fit what we think we should be seeing (the supernovae dimming discussed in the article), and examining the various hypotheses for these data is going to take a long time. It’s clear, too, just how significant the outcome is — that forever accelerating universe is a daunting prospect, as dad2059 points out!

  • Adam March 4, 2008, 5:13

    Hi All

    “Forever” and “infinite” are two terms in cosmology that are much abused and full of philosophical presuppositions. We know preciously zero about the future evolution of the “dark energy” or whatever is accelerating expansion (if it’s being accelerated at all) so to imagine the Great Cosmic Chill-Out as an inevitable end-state is a BIG mistake. An unchanging cosmological constant is the simplest explanation for acceleration – but that’s by no means proven.

    Likewise the assumption that our Universe is an infinite flat-space (Euclidean space) is unproven. A multitude of topologies are possible – the Poincare Duodecahedral for example – but only a few can be confirmed or denied by current observations.

    Even the assumption that the expansion of galaxies is NOT radiating away from Local Group because we’re near the centre, but just looks that way everywhere – well it’s an assumption too. We might be near the Centre, or we might not. The fact that a very simple General Relativistic cosmology produces the same effect without an actual centre is – possibly – mere coincidence.

    I’m not a Steady Stater, I do think we’re in a finite space and I think the Universe is only finite in time – but none of my assumptions can currently rule out any of the other options either.

  • ljk March 9, 2008, 23:40

    Dark Energy and the Accelerating Universe

    Authors: Joshua Frieman (Chicago/Fermilab), Michael Turner (Chicago), Dragan Huterer (Michigan)

    (Submitted on 7 Mar 2008)

    Abstract: The discovery ten years ago that the expansion of the Universe is accelerating put in place the last major building block of the present cosmological model, in which the Universe is composed of 4% baryons, 20% dark matter, and 76% dark energy. At the same time, it posed one of the most profound mysteries in all of science, with deep connections to both astrophysics and particle physics.

    Cosmic acceleration could arise from the repulsive gravity of dark energy — for example, the quantum energy of the vacuum — or it may signal that General Relativity breaks down on cosmological scales and must be replaced.

    We review the present observational evidence for cosmic acceleration and what it has revealed about dark energy, discuss the various theoretical ideas that have been proposed to explain acceleration, and describe the key observational probes that will shed light on this enigma in the coming years.

    Comments: Invited review for Annual Reviews of Astronomy and Astrophysics; 53 pages, 18 figures

    Subjects: Astrophysics (astro-ph)

    Cite as: arXiv:0803.0982v1 [astro-ph]

    Submission history

    From: Dragan Huterer [view email]

    [v1] Fri, 7 Mar 2008 16:00:09 GMT (1488kb)

    http://arxiv.org/abs/0803.0982

  • ljk March 18, 2008, 0:20

    Is dark energy from cosmic Hawking radiation?

    Authors: Jae-Weon Lee, Hyeong-Chan Kim, Jungjai Lee

    (Submitted on 13 Mar 2008)

    Abstract: We suggest that dark energy is the Hawking radiation from a cosmic horizon. Despite of the extremely low Hawking temperature this dark energy could have the appropriate magnitude and the equation of state to explain the observed cosmological data, thank to its huge entropy proportional to the horizon area. If the horizon is an event horizon and the entropy of the radiation satisfies the holographic principle, then the radiation gives the holographic dark energy with the parameter $d\simeq 1$, as observed. Albeit simple, this model could explain many mysteries of dark energy in a consistent way.

    Comments: 5 pages, 1 ig, revtex

    Subjects: High Energy Physics – Theory (hep-th); Astrophysics (astro-ph)

    Cite as: arXiv:0803.1987v1 [hep-th]

    Submission history

    From: Jaeweon Lee Dr. [view email]

    [v1] Thu, 13 Mar 2008 15:05:57 GMT (40kb)

    http://arxiv.org/abs/0803.1987

  • ljk April 2, 2008, 7:14

    Planets and Dark Energy

    Authors: Carl H. Gibson (Univ. Cal. San Diego), Rudolph E. Schild (Harvard)

    (Submitted on 30 Mar 2008)

    Abstract: Self gravitational fluid mechanical methods termed hydro-gravitational-dynamics (HGD) predict plasma fragmentation 0.03 Myr after the turbulent big bang to form protosuperclustervoids, turbulent protosuperclusters, and protogalaxies at the 0.3 Myr transition from plasma to gas. Linear protogalaxyclusters fragment at 0.003 Mpc viscous-inertial scales along turbulent vortex lines or in spirals, as observed. The plasma protogalaxies fragment on transition into white-hot planet-mass gas clouds (PFPs) in million-solar-mass clumps (PGCs) that become globular-star-clusters (GCs) from tidal forces or dark matter (PGCs) by freezing and diffusion into 0.3 Mpc halos with 97% of the galaxy mass. The weakly collisional non-baryonic dark matter diffuses to > Mpc scales and fragments to form galaxy cluster halos. Stars and larger planets form by binary mergers of the trillion PFPs per PGC, mostly on 0.03 Mpc galaxy accretion disks. Stars deaths depend on rates of planet accretion and internal star mixing. Moderate accretion rates produce white dwarfs that evaporate surrounding gas planets by spin-radiation to form planetary nebulae before Supernova Ia events, dimming some events to give systematic distance errors, the dark energy hypothesis, and the Sandage 2006 overestimates of the universe age.

    Comments: 9 pages 8 figures, Practical Problems in Cosmology 2008, St. Petersburg, RU, June 23-27

    Subjects: Astrophysics (astro-ph)

    Cite as: arXiv:0803.4293v1 [astro-ph]

    Submission history

    From: Carl H. Gibson [view email]

    [v1] Sun, 30 Mar 2008 12:38:12 GMT (1006kb)

    http://arxiv.org/abs/0803.4293

  • ljk May 21, 2008, 11:42

    Dark Energy Detected with Supervoids and Superclusters

    Authors: Benjamin R. Granett, Mark C. Neyrinck, István Szapudi (IfA, Hawaii)

    (Submitted on 20 May 2008)

    Abstract: The observed apparent acceleration of the universe is usually attributed to negative pressure from a mysterious dark energy. This acceleration causes the gravitational potential to decay, heating or cooling photons travelling through crests or troughs of large-scale matter density fluctuations. This phenomenon, the late-time integrated Sachs-Wolfe (ISW) effect, has been detected, albeit at low significance, by cross-correlating various galaxy surveys with the Cosmic Microwave Background (CMB).

    Recently, the best evidence has come from the statistical combination of results from multiple correlated galaxy data sets. Here we show that vast structures identified in a galaxy survey project an image onto the CMB; stacking regions aligned with superclusters produces a hot spot, and supervoids, a cold spot. At over 4 sigma, this is the clearest evidence of the ISW effect to date.

    For the first time, our findings pin the effect to discrete structures. The ISW signal from supervoids and superclusters can be combined with other cosmological probes to constrain dark energy and cosmological parameters. In addition, our findings make it more plausible that the extreme Cold Spot and other anomalies in the CMB are caused by supervoids.

    Subjects: Astrophysics (astro-ph)

    Cite as: arXiv:0805.2974v1 [astro-ph]

    Submission history

    From: Mark C. Neyrinck [view email]

    [v1] Tue, 20 May 2008 01:46:10 GMT (957kb)

    http://arxiv.org/abs/0805.2974

  • ljk June 3, 2008, 9:51

    Dark, Perhaps Forever

    New York Times June 3, 2008

    Although cosmologists have adopted
    a cute name, dark energy, for
    whatever is driving this apparently
    antigravitational behavior on the
    part of the universe, nobody claims
    to understand why it is happening,
    or its implications for the future
    of the universe and of the life
    within it, despite thousands of
    learned papers, scores of
    conferences and…

    http://www.kurzweilai.net/email/newsRedirect.html?newsID=8797&m=25748

  • ljk June 24, 2008, 14:14

    Huge lenses to observe cosmic dark energy

    “UK astronomers, as part of an international team, have
    reached a milestone in the construction of one of the largest
    ever cameras to detect the mysterious Dark Energy component
    of the Universe.

    The pieces of glass for the five unique lenses of the camera
    have been shipped from the US to France to be shaped and
    polished into their final form. The largest of the five lenses is
    one metre in diameter, making it one of the largest in the
    world.”

    http://www.spaceref.com/news/viewpr.html?pid=25751