More about Dark Matter and NGC 4555

Chandra's Find Of Lonely Halo Raises Questions About Dark Matter: "Huntsville AL (SPX) Oct 28, 2004
Dark matter continues to confound astronomers, as NASA's Chandra X-ray Observatory demonstrated with the detection of an extensive envelope of dark matter around an isolated elliptical galaxy NGC 4555 (pictured). This discovery conflicts with optical data that suggest a dearth of dark matter around similar galaxies, and raises questions about how galaxies acquire and keep such dark matter halos."