IRAS 17163−3907

The star was discovered and catalogued as emission line star Hen 3–1379 in 1976, and classified as a proto-planetary nebula in 2003 after the 2.2 micron infrared sky survey. Although IRAS 17163-3907 is one of the brightest mid-IR sources in the sky, very few observations were made until 2011 when it was proposed to be at a much larger distance and hence to be a highly luminous object, probably a yellow hypergiant. ==Description==

The picture of the star causing it to be dubbed the Fried Egg Nebula was taken in the mid infrared spectrum by the VISIR instrument in the Very Large Telescope in the Atacama Desert in northern Chile. The filters passed light of frequencies 12,810 nm (mapped to red in the image), 11,850 nm (mapped to green), and 8,590 nm (mapped to blue). The star is about 500,000 times the luminosity of the Sun. The photograph pictured is one of the best ever taken of a yellow hypergiant. The star is eventually expected to end its life in a supernova. ==Shells==

The star is characterized by two visible dusty shells. The inner shell is 4800 AU in diameter and the outer shell is 12,000 AU wide. The properties of these shells are considered similar to those surrounding IRC+10420 (also an evolved massive star suffering heavy mass loss) as well as, for the outer shell, those around luminous blue variables, suggesting both that IRAS 17163−3907 is in a pre-LBV stage and that the ring nebulae that often surround those types of stars may originate with mass loss during the red supergiant stage. ==References==