Durham astronomers' doubts about the "Dark Side"



Universe's content, pie chart

    Figure 1. The standard cosmological model which predicts that the Universe is dominated by 74% dark energy and 22% dark matter. The remaining 4% are the atoms of ordinary matter that we see around us. Thus in this model 96% of the Universe is dark. (Credit: NASA/WMAP Science Team)




WMAP CMB map


    Figure 2. The unresolved radio sources used by Sawangwit & Shanks to measure the effect of telescope smoothing are marked on the WMAP CMB map (open circles). Sawangwit and Shanks found that the radio sources implied stronger telescope smoothing than previously found, suggesting that the CMB ripple size may be smaller. Click the image for larger version (Credit: NASA/WMAP plus Durham University).





ISW effect  

    Figure 3. The effect of foreground superclusters on CMB photons. Two photon paths are shown passing through a galaxy cluster.  Without dark energy (top),  a CMB photon gets gravitationally blueshifted as it enters a cluster and redshifted as it leaves and the two effects cancel. But with dark energy (bottom), the cluster galaxies accelerate away from each other as the photon passes through and the cancellation is not exact, so that slightly higher CMB temperatures are predicted to be observed in sightlines that pass near galaxy superclusters. (Credit: IOP-physicsworld.com)




 the Dark Side, Darth Vader

    Figure 4. Darth Vader from the 'Star Wars' film epic. If the new results are correct then the evidence for the "Dark Side" of the Universe may be less compelling than originally believed! (Darth Vader is TM and copyrighted by Lucasfilm Ltd.)


    Further Information

    The research on the WMAP "ripples" will appear as a letter in the journal Monthly Notices of the Royal Astronomical Society (MNRAS). A preprint of the paper is available on the astrophysics e-print arXiv.
    The research on the test for dark energy via the effect of foreground galaxies on the CMB photons has also appeared in the journal MNRAS (2010MNRAS.402.2228S). The paper can also be found at arXiv:0911.1352.
    A related article which might be of interest can be found at arXiv:1006.1270 (presentation given at the conference "45th Rencontres de Moriond" - Cosmology Session, La Thuile, Val d'Aosta, Italy, March 13 - 20, 2010).
    Expanded press release (original draft) is available here


    Links to some of the press coverage

    BBC World Service; "Newshour" at 13:05 on Sunday 20th June (interview with Prof. John Ellis and Prof. Tom Shanks, started at 39min).
    BBC Radio 4; "The World Tonight" on Friday 18th June (interview with Prof. Tom Shanks, started at 40min).
    Astronomy Now; Say goodbye to dark matter and energy?
    MSNBC; Are dark energy and dark matter not real?
    ScienceNews; Astronomers stoke cosmic debate.
    NewScientist; Has Jupiter sent cosmology down a false trail?
    SPACE.com;  Dark Energy and Dark Matter Might Not Exist, Scientists Allege.
  

       
     (page maintained by Utane Sawangwit, email: utane.sawangwit at durham.ac.uk, last updated 21 June 2010)