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
cloverleaf is rather light emitted from a background
The gravitational field of the visible foreground
galaxy breaks light from this distant
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
Stranger still, the images of the
Einstein Cross vary in relative brightness,
enhanced occasionally by the additional
effect of specific stars in the foreground galaxy.