NGC 7354 - Planetary Nebula
The planetary nebula "NGC 7354" is located in a distance of about 5,500 light years in the constellation Cepheus. It has an apparent brightness of
12.2mag and an apparent size of about 35" - so the PN appears to be about as large as the planet Jupiter. NGC 7354 was discovered in 1787 by F.W.
Herschel.
The nebula's envelope appears elliptical overall, but inside it shows complex structures such as an inner and outer shell, various knots in the
equatorial plane, and two jets. The inner shell is slightly elliptical with an elongation of 1.6:1 and was formed 1,600 years ago. The electron
temperature in this region is 11,000 Kelvin. The outer shell on the other hand is more roundish and even 2,500 years old. Here the temperature
is 14,000 Kelvin. The two shells expand at different speeds, the inner one at 26km/s, the outer one at 35km/s. The two jets even reach particle
velocities of up to 60 kilometers per second.
According to GAIA, the central star has an apparent magnitude of 17.3mag. The temperature is reported to be nearly 100,000 Kelvin. The data also
suggest that the ZS is a binary star, which could explain, among other things, the complex shape of the nebular envelope.
----------------------------------------------------------------------------------------------------------------------------------------------
In a 20 inch telescope NGC 7354 offers a wonderful sight. Through the eyepiece at 270x you see a rather small, roundish nebula that appears quite
bright and has a high surface brightness. The center appears darker and is surrounded by an oval ring located within a roundish envelope. Two faint
knots are visible on the southeast side, and another on the opposite side.
A central star is not visible, but some brighter stars are noticeable in the near vicinity.
