Explanation: Albert Einstein's
general theory of relativity, published 100 years
ago this month, predicted the phenomenon of gravitational lensing.
And that's what gives these distant galaxies such a whimsical appearance,
through the looking glass of X-ray and optical
image data from the Chandra and Hubble space telescopes.
Nicknamed the Cheshire Cat galaxy group, the group's two
large elliptical galaxies are suggestively framed by arcs.
The arcs are optical images
of distant background galaxies
lensed by the foreground group's total distribution
of gravitational mass dominated by dark matter.
In fact the two large elliptical "eye" galaxies represent
the brightest members of their own galaxy groups which are merging.
Their relative collisional speed of nearly 1,350 kilometers/second
heats gas to millions of degrees producing the X-ray glow shown
in purple hues.
galaxy group mergers?
The Cheshire Cat
in the constellation Ursa Major, some 4.6 billion light-years away.