Abell 3376: A cluster of galaxies about 614 million light years
from Earth. Caption: This composite image of the galaxy cluster
Abell 3376 combines Chandra and ROSAT X-ray data (gold), an
optical image from the Digitized Sky Survey (red, green and
blue), and a radio image from the VLA (blue). Two different
teams used Chandra observations of galaxy clusters – including
Abell 3376 -- to study the properties of gravity on cosmic
scales and test Einstein's theory of General Relativity. Such
studies are crucial for understanding the evolution of the
Universe, both in the past and the future, and for probing the
nature of dark energy, one of the biggest mysteries in science.
Scale: Image is 29 arcmin across (about 5 million light years
across). Chandra X-ray Observatory