Bullet cluster (1E 0657-56), X-ray image. The bullet cluster, which lies in the constellation Carina, contains two colliding galaxies. The normal matter in the cluster is shown here in pink. Background material is also visible as a result of gravitational lensing, or the distortion of light by the huge mass of the galaxies. This reveals dark matter, matter that does not emit or reflect visible light or radiation, but can only be detected by its gravitational effects on normal matter. This is shown here in blue. This image was taken by the Chandra X-ray Observatory, a telescope orbiting Earth.