in front of the bulge of the galaxy. This dust lane is actually a symmetrical ring that encloses the bulge of the galaxy. Most of the cold atomic hydrogen gas and the dust lie within this ring. The ring might also contain most of the Sombrero Galaxy's cold molecular gas, although this is an inference based on observations with low resolution and weak detections. Additional observations are needed to confirm that the Sombrero galaxy's molecular gas is constrained to the ring. Based on infrared spectroscopy, the dust ring is the primary site of star formation within this galaxy. Nucleus The nucleus of the Sombrero Galaxy is classified as a low-ionization nuclear emission-line region (LINER). These are nuclear regions where ionized gas is present, but the ions are only weakly ionized (i.e. the atoms are missing relatively few electrons). The source of energy for ionizing the gas in LINERs has been debated extensively. Some LINER nuclei may be powered by hot, young stars found in star formation regions, whereas other LINER nuclei may be powered by active galactic nuclei (highly energetic regions that contain supermassive black holes). Infrared spectroscopy observations have demonstrated that the nucleus of the Sombrero Galaxy is probably devoid of any significant star formation activity. However, a supermassive black hole has been identified in the nucleus (as discussed in the subsection below), so this active galactic nucleus is probably the energy source that weakly ionizes the gas in the Sombrero Galaxy. Central supermassive black hole In the 1990s, a research group led by John Kormendy demonstrated that a supermassive black hole is present within the Sombrero Galaxy. Using spectroscopy data from both the CFHT and the Hubble Space Telescope, the group showed that the speed of revolution of the stars within the center of the galaxy could not be maintained unless a mass 1 billion times that of the Sun, , is present in the center. This is among the most massive black holes measured in any nearby galaxy, and is the nearest billion-solar-mass black hole to Earth. Synchrotron radiation At radio and X-ray wavelengths, the nucleus is a strong source of synchrotron radiation. Synchrotron radiation is produced when high-velocity electrons oscillate as they pass through regions with strong magnetic fields. This emission is quite common for active galactic nuclei. Although radio synchrotron radiation may vary over time for some active galactic nuclei, the luminosity of the radio