Supernova 1987A imaged in X-rays by the XMM-Newton spacecraft. X-rays are produced when the expanding shock wave interacts with surrounding materiel. Astronomers have found many such bubbles around supernova remnants. Though supernovae are expected to have neutron stars at their centres, none has been found for 1987A. Some astronomers speculate that the core has collapsed completely into a Black Hole.
When all the galaxies, including "dark" mass, are weighed the total is only about 30% of the mass necessary to close the Universe. This has fueled more speculation about a "dark energy." Observations of clusters by Alain Blanchard's team indicate that dark matter is 4 times as prevalent as thought, comprise the 95% of mass that is not baryons. But where is it?
Radio astronomers have found entire dark galaxies in the vicinity of the Milky Way and Andromeda. These galaxies are composed entirely of "dark" mass. These have been found because they are relatively nearby. A dwarf spheroidal galaxy called Tucana exists far from any visible galaxy. No astronomer knows how many more dark galaxies are out there.
In this month's SCIENTIFIC AMERICAN astronomers Wallace Tucker, Harvey Tananbaum and Andrew Fabian write about immense Black Holes at the centres of galaxy clusters. These Black Holes create immense bubbles of high-energy particles, like a supernova but 100 million times more powerful! Tananbaum is director of the Chandra X-ray Centre and will be principal investigator of the CONSTELLATION-X spacecraft, assuming "dark energy" doesn't delay the project.
It is comforting to see similiar processes working at a variety of scales. Black Holes have a huge influence on structure, from stars to galaxy clusters. Could they get any bigger? Astronomers Margaret Geller, John Huchra and the Sloan Digital Sky Survey have shown that galaxies are arranged in enormous walls with bubble-shaped voids in between. These could be home to ultra-massive BIG GULP Black Holes. Early in the Universe's history they would have swallowed everything within reach, leaving behind great voids. The missing mass ascribed to "dark energy" could be hidden in those voids.
Big Gulp Black Holes would swallow any radiation and be nearly impossible to detect visually. They could be detected by their immense magnetic fields. Astronomers have found powerful magnetic fields of unknown origin in intergalactic Space. Those fields may be the sign of the Universe's missing mass.