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The concept of a Universe undergoing an acceleration in its expansion rate and predicating the existence of dark energy is based on observed deficits in brightness of Type 1a supernovae at high redshifts, amounting to Δ m∼0.3–0.5. We show that the effect of intergalactic graphite whiskers of radii in the general range 0.03–0.07 μm and lengths in excess of ∼5 μm will be to mimic the effects of dark energy in the redshift magnitude relation for Type 1a supernovae. The mean intergalactic density of whiskers required for such an effect is ∼3×10−34 g cm−3, about 10−5 of the critical closure density. [ABSTRACT FROM AUTHOR]

Comparison of recent spectra by V. Motta et al. (V. Motta et al.: Astrophys. J. 574, 719–725) of two images of a distant gravitationally lensed quasar ( z = 1.38) leads to an extinction curve of the lens galaxy ( z = 0.83) showing clear evidence of a 2175A absorption feature. We compare these data with measured extinction curves from the Galaxy, LMC and SMC and with predictions from models. As it has been found by other authors in the Local Group galaxies we found that the SBS 0909 + 532 curve is compatible with three component models of classical spherical grains and PAHs. We note that apart from this standard point of view, the fits also admit an interpretation in terms of products of a biological origin involving three grain components. [ABSTRACT FROM AUTHOR]