NGC 2440 is a planetary nebula ejected by a dying star. The central star of the nebula is one of the hottest known, with a surface temperature near 200,000 degrees Celsius. The nebula glows because of fluorescence due to ultraviolet radiation from the hot star. NGC 2440 is rich in clouds of dust, some of which form long, dark streaks pointing away from the central star. This nebula is located about 4,000 light-years from Earth in the direction of the constellation Puppis.