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