Astronomy characteristics of the resulting star depend primarily upon its starting mass. The more massive the star, the greater its luminosity, and the more rapidly it fuses its hydrogen fuel into helium in its core. Over time, this hydrogen fuel is completely converted into helium, and the star begins to evolve. The fusion of helium requires a higher core temperature. A star with a high enough core temperature will push its outer layers outward while increasing its core density. The resulting red giant formed by the expanding outer layers enjoys a brief life span, before the helium fuel in the core
Fleming 1 a torus of expanding hot gas forming the inner bright ellipse. Fleming 1 is probably 5,000 years old. Like any other planetary nebula Fleming 1 was formed when an old asymptotic giant branch (AGB) star lost its outer hydrogen-rich envelope, leaving behind a hot core (young white dwarf)—the central star of the nebula. The star in the center of Fleming 1 has a temperature of and mass of 0.56 . Observations performed by European Southern Observatory showed that the central star is in fact a double degenerate (made of two white dwarfs) binary with a period of days. The companion