Courtesy of ESA and the Hubble Space Telescope, here is the explosion of the Crab Nebula visible from Earth in 1054 AD. We use supernovae to distinguish between cosmological theories. As you know, the apparent acceleration of redshifts has led some smart people down the wrong path.
Steinn Siggurdson has some excellent posts about the NASA Beyond Einstein programme, which I am associated with. There may be a showdown for launch slots between a Joint Dark Energy Mission, the Constellation X-Ray Observatory, and the LISA gravitational wave experiment. You know what this writer thinks of "dark energy."
Someone let me know if I am including too many videos or if the loading time of this blog is getting slow.