Fleming 1 is an unusual

planetary nebula A planetary nebula (PN, plural PNe) is a type of emission nebula consisting of an expanding, glowing shell of ionized gas ejected from red giant stars late in their lives. The term "planetary nebula" is a misnomer because they are unrelated to ...

situated in the

Centaurus constellation Centaurus is a bright constellation in the southern sky. One of the largest constellations, Centaurus was included among the 48 constellations listed by the 2nd-century astronomer Ptolemy, and it remains one of the 88 modern constellations. ...

. It has a pair of symmetrical jets spanning more than 2.8 pc and delineated with a number of knots. The jets and knots are moving away from the center of the nebula and were probably ejected 10,000 to 16,000 years ago. The innermost part of the nebula has a butterfly shape and is immersed into a faint halo. The butterfly's wings point in the direction of jets with their axis titled by 50° to the line of sight. The waist of the "butterfly" is surrounded by 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 The asymptotic giant branch (AGB) is a region of the Hertzsprung–Russell diagram populated by evolved cool luminous stars. This is a period of stellar evolution undertaken by all low- to intermediate-mass stars (about 0.5 to 8 solar masses) lat ...

(AGB) star lost its outer hydrogen-rich envelope, leaving behind a hot core (young

white dwarf A white dwarf is a stellar core remnant composed mostly of electron-degenerate matter. A white dwarf is very dense: its mass is comparable to the Sun's, while its volume is comparable to the Earth's. A white dwarf's faint luminosity comes fro ...

)—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 The European Organisation for Astronomical Research in the Southern Hemisphere, commonly referred to as the European Southern Observatory (ESO), is an intergovernmental organization, intergovernmental research organisation made up of 16 mem ...

showed that the central star is in fact a double degenerate (made of two white dwarfs) binary with a period of days. The companion is probably an older white dwarf of a higher mass—0.64 to 0.7 . Its temperature is about 120,000 K providing the bulk of high energy photons needed to ionize the nebula. The jets likely formed as a result of accretion of the material from the AGB star onto this white dwarf. The accretion led to the formation of a precessing

accretion disk An accretion disk is a structure (often a circumstellar disk) formed by diffuse material in orbital motion around a massive central body. The central body is typically a star. Friction, uneven irradiance, magnetohydrodynamic effects, and other fo ...

, which was expelling material along its rotational axis leading to the formation of jets and knots. The past accretion events also explain the high temperature of the second white dwarf.

References

{{DEFAULTSORT:Fleming 1 Planetary nebulae Centaurus (constellation)