November 7, 2006

Gravity helps SDSS-II reveal a brilliant jewel of the early universe

Sahar Allam of Fermilab searched more than 70,000 SDSS-II images looking for merging pairs of galaxies. Allam recognized this as an arc of three images of the same background galaxy, gravitationally lensed by the luminous red elliptical in the foreground. (The faint blob at the lower left is a random galaxy in the field). A combination of furious star formation and gravitational amplification makes the 8 O'Clock Arc three times brighter than the brightest previously known Lyman break galaxy, another gravitationally lensed system known as cB58.
(Credit - Allam, SDSS-II collaboration)

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