Period 6 element devices though concerns about the element's toxicity have led to mercury thermometers and sphygmomanometers being largely phased out in clinical environments in favor of alcohol-filled, galinstan-filled, digital, or thermistor-based instruments. It remains in use in scientific research applications and in amalgam material for dental restoration. It is used in lighting: electricity passed through mercury vapor in a phosphor tube produces short-wave ultraviolet light which then causes the phosphor to fluoresce, making visible light. Thallium is a chemical element with the symbol Tl and atomic number 81. This soft gray other metal resembles tin but discolors when exposed to air. The
SN 2005bc of the supernova at around −18.6 at maximum, rather faint for a Type Ia event. As the supernova was of Type Ia, its progenitor star was a White Dwarf star which exceeded the Chandrasekhar limit. Below is an image of SN 2005bc and NGC 5698 taken just over a week after peak brightness. SN 2005bc SN 2005bc was a Type Ia supernova occurring in the Barred spiral galaxy NGC 5698 in the constellation of Boötes. SN 2005bc was discovered on 2 April 2005 by LOSS and independently by Tim Puckett and L. Cox. The supernova was at magnitude 16.4 at