Simeis 22

Simeis 22

Nebula
Observation data: J2000 epoch
Right ascension	17^h 58^m 10^s
Declination	−31° 42′ 55″
Distance	715 ly
Constellation	Cassiopeia
Designations	PN G128.0-04.1,[1] Sh 2-188
See also: Lists of nebulae

Simeis 22, also known as the Firefox Nebula,^[2] is an planetary nebula in Cassiopeia. It was discovered in the early 1950s by Grigory Shajn and Vera Gaze. It was independently discovered by Stewart Sharpless. It was first thought to be a supernova remnant, and was then thought to be a planetary nebula. ^[3]

The nebula is brightest towards the southwest, since that is the direction the central star is moving.^[4] The nebula is a prominent example of interaction with the interstellar medium, as the gasses being pushed by the central star are also pushing against interstellar gasses, resulting in increased density and mass, which creates a bow shock.^[5] At the edges of the bow shock, whirlpool like structures have formed.^[6]

References

1. "Dictionary of Nomenclature of Celestial Objects".
2. "Firefox Nebula".
3. "Planetary Nebula Simeis 22".
4. "Sharpless 2-188 (Sh2-188)".
5. Wareing, C.J.; O'Brien, T.J.; Zijlstra, Albert A.; Kwitter, K.B.; Irwin, J.; Wright, N.; Griemel, R.; Drew, J.E. "The shaping of planetary nebula Sh2-188 through interactionwith the interstellar medium".
6. "A Whirlpool in the Wake Left by a Dying Star".