by neufer » Sun Oct 21, 2018 7:00 pm
https://en.wikipedia.org/wiki/Cat%27s_Eye_Nebula wrote:
<<The Cat's Eye Nebula's small bright inner nebula subtends an average of 16.1 arcsec, with the outer prominent condensations about 25 arcsec. Deep images reveal an extended halo about 5 arcmin [~4.4 lyr] across, that was once ejected by the central progenitor star during its red giant phase.
https://www.astrobin.com/109858/
Cat's Eye Nebula : RA 17h 58m 33.423s, DEC +66° 37′ 59.52″
North Ecliptic Pole: RA 18h 00m 00.00s, DEC +66° 33′ 38.55″
NGC 6543 is just 4.4 arcmin from the current position of the North Ecliptic Pole(, less than 1⁄10 of the 45 arc minutes between Polaris and the current location of the Earth's northern axis of rotation). It is a convenient and accurate marker for the axis of rotation of the Earth's ecliptic, around which the celestial North Pole rotates. It is also a good marker for the nearby “invariable” axis of the solar system, which is the center of the circles which every planet's north pole, and the north pole of every planet's orbit, make in the sky. Its position as an ecliptic pole station marker is essentially permanent on the time-scale of human history, as opposed to the Pole Star, which changes every few thousand years.
Observations show the bright nebulosity has temperatures between 7000 and 9000 K, whose densities average of about 5000 particles per cubic centimetre. Its outer halo has the higher temperature around 15000 K, but is of much lower density. Velocity of the fast stellar wind is about 1900 km/s, where spectroscopic analysis shows the current rate of mass loss averages 3.2×10
−7 solar masses per year.
Surface temperature for the central PNN is about 80000 K, being 10000 times as luminous as the sun. Stellar classification is O7 + [WR]–type star. Calculations suggest the PNN is over one solar mass, from a theoretical initial 5 solar masses. The central Wolf-Rayet star has a radius of 0.65 R
☉. The Cat's Eye Nebula, given in some sources, lies about three thousand light-years from Earth.>>
[quote=" https://en.wikipedia.org/wiki/Cat%27s_Eye_Nebula"]
[float=left][img3="Precession of Earth's axis around the North Ecliptic Pole/Cat's Eye Nebula"]https://upload.wikimedia.org/wikipedia/commons/thumb/1/16/Precession_N.gif/1024px-Precession_N.gif[/img3][/float]
<<The Cat's Eye Nebula's small bright inner nebula subtends an average of 16.1 arcsec, with the outer prominent condensations about 25 arcsec. Deep images reveal an extended halo about 5 arcmin [~4.4 lyr] across, that was once ejected by the central progenitor star during its red giant phase.
https://www.astrobin.com/109858/
[b][color=#FF0000]Cat's Eye Nebula : RA 17h 58m 33.423s, DEC +66° 37′ 59.52″
North Ecliptic Pole: RA 18h 00m 00.00s, DEC +66° 33′ 38.55″[/color][/b]
:arrow: [b][color=#0000FF]NGC 6543 is just 4.4 arcmin from the current position of the North Ecliptic Pole(, less than 1⁄10 of the 45 arc minutes between Polaris and the current location of the Earth's northern axis of rotation). It is a convenient and accurate marker for the axis of rotation of the Earth's ecliptic, around which the celestial North Pole rotates. It is also a good marker for the nearby “invariable” axis of the solar system, which is the center of the circles which every planet's north pole, and the north pole of every planet's orbit, make in the sky. Its position as an ecliptic pole station marker is essentially permanent on the time-scale of human history, as opposed to the Pole Star, which changes every few thousand years.[/color][/b]
Observations show the bright nebulosity has temperatures between 7000 and 9000 K, whose densities average of about 5000 particles per cubic centimetre. Its outer halo has the higher temperature around 15000 K, but is of much lower density. Velocity of the fast stellar wind is about 1900 km/s, where spectroscopic analysis shows the current rate of mass loss averages 3.2×10[sup]−7[/sup] solar masses per year.
Surface temperature for the central PNN is about 80000 K, being 10000 times as luminous as the sun. Stellar classification is O7 + [WR]–type star. Calculations suggest the PNN is over one solar mass, from a theoretical initial 5 solar masses. The central Wolf-Rayet star has a radius of 0.65 R[sub]☉[/sub]. The Cat's Eye Nebula, given in some sources, lies about three thousand light-years from Earth.>>[/quote]