V. The Cat’s Eye Nebula
One of the most famous nebulae is the Cat’s Eye Nebula (NGC-6543); it was discovered by William Herschel in 1786. NGC-6543 is located in the northern constellation of Draco; it appears as a blooming center with surrounding and expanding rings. The NGC-6543 has a historical importance because it was the first nebula to be studied spectroscopically by the astronomer William Huggins in 1864; this study revealed the distinctions between PNe and the other gaseous nebulae. When Huggins studied the spectrum of NGC-6543, he found that the spectrum is dominated by discontinuous lines, emission spectrum, rather than continuous like in the stellar spectrum. The first identified line was the hydrogen Balmer line (H). This discontinuous spectrum confirms Herschel’s idea that the PN gets its energy from a nearby star. Moreover, when Hubble in 1922 found a relation between the magnitude of the central star and the size of the PN, he proposed that the emission spectrum of PN is the result of the absorption of the continuous spectrum of its central star’s radiation (Kwok). …show more content…
Some images for NGC-6543 were taken by the Hubble Space Telescope (HST); these images exposed more details about the structure of the glowing center and the expanding shells of the nebula. The central star is found to be of spectral type O7+WR that has a temperature of 80 000 K and a mass loss rate of 3.2 10-7 M* yr-1 (Wesson & Liu 2004). Also, using two HST’s images separated by three years along with the spectroscopically obtained expansion velocities, astronomers were able to detect the optical expansion parallax of NGC-6543 and derive a distance to NGC-6543 of 1001± 269 pc and a deduced kinematic age of 1039 ± 259 yr (Reed et al.
One of the most famous nebulae is the Cat’s Eye Nebula (NGC-6543); it was discovered by William Herschel in 1786. NGC-6543 is located in the northern constellation of Draco; it appears as a blooming center with surrounding and expanding rings. The NGC-6543 has a historical importance because it was the first nebula to be studied spectroscopically by the astronomer William Huggins in 1864; this study revealed the distinctions between PNe and the other gaseous nebulae. When Huggins studied the spectrum of NGC-6543, he found that the spectrum is dominated by discontinuous lines, emission spectrum, rather than continuous like in the stellar spectrum. The first identified line was the hydrogen Balmer line (H). This discontinuous spectrum confirms Herschel’s idea that the PN gets its energy from a nearby star. Moreover, when Hubble in 1922 found a relation between the magnitude of the central star and the size of the PN, he proposed that the emission spectrum of PN is the result of the absorption of the continuous spectrum of its central star’s radiation (Kwok). …show more content…
Some images for NGC-6543 were taken by the Hubble Space Telescope (HST); these images exposed more details about the structure of the glowing center and the expanding shells of the nebula. The central star is found to be of spectral type O7+WR that has a temperature of 80 000 K and a mass loss rate of 3.2 10-7 M* yr-1 (Wesson & Liu 2004). Also, using two HST’s images separated by three years along with the spectroscopically obtained expansion velocities, astronomers were able to detect the optical expansion parallax of NGC-6543 and derive a distance to NGC-6543 of 1001± 269 pc and a deduced kinematic age of 1039 ± 259 yr (Reed et al.