Figure 2-16 RIVUXG The Nebula N44 Stretching about 1,000 light-years across, this glowing gas cloud shown here is not within our Milky Way Galaxy, but in the nearby Large Magellanic Cloud about 170,000 light-years away. Hot stars within the nebula emit high-energy, ultraviolet photons, which are absorbed by the surrounding gas and heat the gas to high temperature. This heated gas produces light with an emission line spectrum. The particular wavelength of red light emitted by the nebula is characteristic of hydrogen gas. (WFI, MPG/ESO 2.2-m Telescope, La Silla, ESO)