This is an infrared image of the nebula. Because most infrared emission is absorbed in the EarthΓÇÖs atmosphere, the best infrared images are taken from Earth-orbiting satellites. Infrared emission is invisible, so astronomers use false colors to distinguish one area of radiation from another. In this image, blue designates the warmest areas, green the cooler ones, and red the coldest. The strongest infrared radiation comes from the shell of gas in the Homunculus Nebula, which envelops Eta Carinae. Eta Carinae ΓÇ£heatsΓÇ¥ the nebula to about 250 degrees Kelvin (23 degrees below the freezing point of water). At this temperature the nebula is too cool to emit much visible light, but it is easily detected by its infrared
