Bipolar nebula

Bipolar planetary nebula PN Hb 12.^[1]

A bipolar nebula is a distinctive nebular formation characterized by an axially symmetric bi-lobed appearance.

Many, but not all, planetary nebulae exhibit an observed bipolar structure. It may be that the two types of nebulae are directly related, one preceding or superseding the other in the evolution of the nebula.

Formation

Though the exact causes of this nebular structure are not known, it may be related to the physical process known as bipolar outflow in which a star ejects highly energetic streams of outflow along both poles. One theory states that these outflows collide with material surrounding the star (either stellar dust, or shells of matter sloughed off in a prior Supernova event).

Examples

Planetary Nebula M2-9, otherwise known as the Twin Jet Nebula or the Wings of a Butterfly Nebula, is a good example of a bipolar or two-lobed nebula.

• Homunculus Nebula around Eta Carinae ^[2][3][4][5]
• Hubble 5 ^[6]
• M2-9 – The Wings of a Butterfly Nebula ^[7][8][9]
• OH231.8+4.2 – The Calabash Nebula or Rotten Egg Nebula ^{[10][11][11][12][13]}
• Mz3 (or Menzel 3) – The Ant Nebula ^[14][15][16]
• CRL 2688 – The Egg Nebula ^{[17][18][19][20]}
• HD 44179 – The Red Rectangle Nebula ^[21][22][23]
• MyCn18 – The Hourglass Nebula ^{[24][25][26][27][28]}
• He2-104 – The Southern Crab Nebula ^[29][30][31]
• The Boomerang Nebula ^{[32][33][34][35][36]}
• NGC 2346 – Also known as Butterfly NGC 2346 ^[37]

References

See also

• Bipolar outflow
• Stellar evolution