APOD: Halo of the Cat's Eye (2018 Oct 20)

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APOD: Halo of the Cat's Eye (2018 Oct 20)

Post by APOD Robot » Sat Oct 20, 2018 4:09 am

[img]https://apod.nasa.gov/apod/calendar/S_181020.jpg[/img] Halo of the Cat's Eye

Explanation: Not a Falcon 9 rocket launch after sunset, the Cat's Eye Nebula (NGC 6543) is one of the best known planetary nebulae in the sky. Its haunting symmetries are seen in the very central region of [url=http://www.robgendlerastropics.com/NGC6543-BYU.html" >this composited picture</a>, processed to reveal an enormous but extremely faint halo of gaseous material, over three light-years across. Made with data from ground- and space-based telescopes it shows the extended emission which surrounds the brighter, familiar <a href="http://en.wikipedia.org/wiki/Planetary_nebula]planetary nebula[/url]. Planetary nebulae have long been appreciated as a final phase in the life of a sun-like star. But only more recently have some planetaries been found to have halos like this one, likely formed of material shrugged off during earlier active episodes in the star's evolution. While the planetary nebula phase is thought to last for around 10,000 years, astronomers estimate the outer filamentary portions of this halo to be 50,000 to 90,000 years old.

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Re: APOD: Halo of the Cat's Eye (2018 Oct 20)

Post by Guest » Sat Oct 20, 2018 5:18 am

I posted a reply but it got eaten. The web site is having problems at the moment. And no, it is not that I overlooked that stupid validation question; at least that does not eat the reply.

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Re: APOD: Halo of the Cat's Eye (2018 Oct 20)

Post by De58te » Sat Oct 20, 2018 9:25 am

Could we assume by the first line in the explanation that it is a Falcon 9 Rocket launch BEFORE sunset?

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Re: APOD: Halo of the Cat's Eye (2018 Oct 20)

Post by Ann » Sat Oct 20, 2018 9:53 am


Starsurfer, where are you? Maybe the coffee mug I have posted is your cup of tea, but today's APOD gives you your cup of tea with a stunning halo to boot! :D

Ann
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Re: APOD: Halo of the Cat's Eye (2018 Oct 20)

Post by heehaw » Sat Oct 20, 2018 11:58 am

Fascinating insight into the last phases of stellar evolution!

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Re: APOD: Halo of the Cat's Eye (2018 Oct 20)

Post by orin stepanek » Sat Oct 20, 2018 2:13 pm

Oh Wow! Stands out in my mind; as one of APOD's most beautiful! :D 8-) :thumb_up:
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Re: APOD: Halo of the Cat's Eye (2018 Oct 20)

Post by saturno2 » Sat Oct 20, 2018 4:34 pm

Interesting image

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Re: APOD: Halo of the Cat's Eye (2018 Oct 20)

Post by starsurfer » Sat Oct 20, 2018 5:37 pm

Ann wrote:
Sat Oct 20, 2018 9:53 am

Starsurfer, where are you? Maybe the coffee mug I have posted is your cup of tea, but today's APOD gives you your cup of tea with a stunning halo to boot! :D

Ann
I'm over here and yes I totally love this image! Here's to more PN haloes being photographed in the future.

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Re: APOD: Halo of the Cat's Eye (2018 Oct 20)

Post by zendae1 » Sat Oct 20, 2018 8:43 pm

A facsimile of that amazing center would make a beautiful pendant.

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Re: APOD: Halo of the Cat's Eye (2018 Oct 20)

Post by Fred the Cat » Sat Oct 20, 2018 11:07 pm

Part of the halo seems to have a straight edge?
Cat eye_LI (2).jpg
Not something you'd expect. A result of processing :?:
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Re: APOD: Halo of the Cat's Eye (2018 Oct 20)

Post by Chris Peterson » Sat Oct 20, 2018 11:34 pm

Fred the Cat wrote:
Sat Oct 20, 2018 11:07 pm
Part of the halo seems to have a straight edge?
Cat eye_LI (2).jpg
Not something you'd expect. A result of processing :?:
The center portion is a Hubble image. The outer portion is a wider field ground-based image. I expect you're just seeing a bit of the stitching showing through.
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Re: APOD: Halo of the Cat's Eye (2018 Oct 20)

Post 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″


:arrow: 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.>>
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Re: APOD: Halo of the Cat's Eye (2018 Oct 20)

Post by BDanielMayfield » Mon Oct 22, 2018 12:51 pm

Chris Peterson wrote:
Sat Oct 20, 2018 11:34 pm
Fred the Cat wrote:
Sat Oct 20, 2018 11:07 pm
Part of the halo seems to have a straight edge?
Cat eye_LI (2).jpg
Not something you'd expect. A result of processing :?:
The center portion is a Hubble image. The outer portion is a wider field ground-based image. I expect you're just seeing a bit of the stitching showing through.
Maybe, but I can see two more straight line effects that cut across the one Fred pointed out.

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