Astronomy Picture of the Day
    


The Einstein Cross Gravitational Lens
<< Yesterday 10.03.2007 Tomorrow >>
The Einstein Cross Gravitational Lens
Credit & Copyright: J. Rhoads (ASU) et al., WIYN, AURA, NOAO, NSF
Explanation: Most galaxies have a single nucleus -- does this galaxy have four? The strange answer leads astronomers to conclude that the nucleus of the surrounding galaxy is not even visible in this image. The central cloverleaf is rather light emitted from a background quasar. The gravitational field of the visible foreground galaxy breaks light from this distant quasar into four distinct images. The quasar must be properly aligned behind the center of a massive galaxy for a mirage like this to be evident. The general effect is known as gravitational lensing, and this specific case is known as the Einstein Cross. Stranger still, the images of the Einstein Cross vary in relative brightness, enhanced occasionally by the additional gravitational microlensing effect of specific stars in the foreground galaxy.

January
February
March
April
May
June
July
August
September
October
November
December
 < March 2007  >
Mo Tu We Th Fr Sa Su



1234
567891011
12131415161718
19202122232425
262728293031
Authors & editors: Robert Nemiroff (MTU) & Jerry Bonnell (USRA)
NASA Web Site Statements, Warnings, and Disclaimers
NASA Official: Jay Norris. Specific rights apply.
A service of: LHEA at NASA / GSFC
& Michigan Tech. U.

Based on Astronomy Picture Of the Day

Publications with keywords: gravitational lens - spiral galaxy - quasar
Publications with words: gravitational lens - spiral galaxy - quasar
See also:
All publications on this topic >>