27 June 2002

Gravitational lensing: Seeing red

The Sloan Digital Sky Survey has discovered exceptionally bright quasars with redshifts of up to 6.28. The brightness of a quasar scales roughly
with the mass of the central black hole; it is puzzling how so many bright
quasars formed so soon after the Big Bang. A new analysis suggests that up to
one-third of them are actually made to appear much brighter than they really are due to gravitational lensing by galaxies along the line of sight.

Magnification of light from many distant quasars by gravitational lenses
J. STUART B. WYITHE & ABRAHAM LOEB
Nature 417, 923–925 (2002); doi:10.1038/nature00794
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Astronomy: Through a lens brightly
EDWIN L. TURNER
Gravitational lensing of light from some of the most distant objects known could be more widespread than had been thought. If so, it could be good — and bad — news for cosmologists.
Nature 417, 905–906 (2002); doi:10.1038/417905a
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