APOD: The Helix Nebula from CFHT (2018 Jan 03)

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APOD: The Helix Nebula from CFHT (2018 Jan 03)

Post by APOD Robot » Wed Jan 03, 2018 5:05 am

Image The Helix Nebula from CFHT

Explanation: Will our Sun look like this one day? The Helix Nebula is one of brightest and closest examples of a planetary nebula, a gas cloud created at the end of the life of a Sun-like star. The outer gasses of the star expelled into space appear from our vantage point as if we are looking down a helix. The remnant central stellar core, destined to become a white dwarf star, glows in light so energetic it causes the previously expelled gas to fluoresce. The Helix Nebula, given a technical designation of NGC 7293, lies about 700 light-years away towards the constellation of the Water Bearer (Aquarius) and spans about 2.5 light-years. The featured picture was taken with the Canada-France-Hawaii Telescope (CFHT) located atop a dormant volcano in Hawaii, USA. A close-up of the inner edge of the Helix Nebula shows complex gas knots of unknown origin.

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Re: APOD: The Helix Nebula from CFHT (2018 Jan 03)

Post by Boomer12k » Wed Jan 03, 2018 7:07 am

I am wondering if gas and dust "knotted up" as the expanding shell hit the interstellar medium... it would push away lesser dense material and areas, and leave....well...."streaks".... just my guess at the moment.

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Re: APOD: The Helix Nebula from CFHT (2018 Jan 03)

Post by ta152h0 » Wed Jan 03, 2018 11:08 am

Wolf Kotenberg

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Re: APOD: The Helix Nebula from CFHT (2018 Jan 03)

Post by Ann » Wed Jan 03, 2018 12:46 pm

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Re: APOD: The Helix Nebula from CFHT (2018 Jan 03)

Post by neufer » Wed Jan 03, 2018 12:50 pm

Boomer12k wrote:
I am wondering if gas and dust "knotted up" as the expanding shell hit the interstellar medium... it would push away lesser dense material and areas, and leave....well...."streaks".... just my guess at the moment.
  • Probably an earlier ejection stage threw out (up?) a slow moving shell that was overtaken by a later ejection shell.
https://en.wikipedia.org/wiki/Helix_Nebula wrote: <<The Helix Nebula was the first planetary nebula discovered to contain cometary knots. Its main ring contains knots of nebulosity, which have now been detected in many nearby planetaries. These knots are highly radially symmetric (from the PNN) and are described as "cometary", each centered on a core of neutral molecular gas and containing bright cusps (local photoionization fronts) towards the central star and tails away from it. All tails extend away from the PNN in a radial direction. Excluding the tails, they are (very approximately) the size of the Solar system, while each of the cusp knots are optically thick due to Lyc photons from the PNN. There are more than 20,000 cometary knots estimated to be in the Helix Nebula.

The excitation temperature varies across the Helix nebula. The rotational-vibrational temperature ranges from 1800 K in a cometary knot located in the inner region of the nebula are about 2.5′ (arcmin) from the central PNN, calculated at about 900 K in the outer region at the distance of 5.6′.>>
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Re: APOD: The Helix Nebula from CFHT (2018 Jan 03)

Post by ellipseshadow » Wed Jan 03, 2018 5:52 pm

The plural of gas is gases. Gasses is a verb. The correct word to use in this article is gases.

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Re: APOD: The Helix Nebula from CFHT (2018 Jan 03)

Post by geckzilla » Wed Jan 03, 2018 6:04 pm

ellipseshadow wrote:The plural of gas is gases. Gasses is a verb. The correct word to use in this article is gases.
I do not share this usage constraint. Apparently neither does Merriam-Webster https://www.merriam-webster.com/dictionary/gasses
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Re: APOD: The Helix Nebula from CFHT (2018 Jan 03)

Post by bystander » Wed Jan 03, 2018 6:07 pm

ellipseshadow wrote:The plural of gas is gases. Gasses is a verb. The correct word to use in this article is gases.
"gasses" is an acceptable variant of the plural form of "gas", especially in British spelling.
Know the quiet place within your heart and touch the rainbow of possibility; be
alive to the gentle breeze of communication, and please stop being such a jerk.
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Re: APOD: The Helix Nebula from CFHT (2018 Jan 03)

Post by neufer » Wed Jan 03, 2018 6:24 pm

bystander wrote:
geckzilla wrote:
ellipseshadow wrote:
The plural of gas is gases. Gasses is a verb. The correct word to use in this article is gases.
I do not share this usage constraint. Apparently neither does Merriam-Webster https://www.merriam-webster.com/dictionary/gasses
"gasses" is an acceptable variant of the plural form of "gas", especially in British spelling.
https://en.wikipedia.org/wiki/Gaslighting wrote:
<<Gaslighting is a form of manipulation that seeks to sow seeds of doubt in a targeted individual hoping to make them question their own memory, perception, and sanity. The term originates in the systematic psychological manipulation of a victim by the main character in the 1938 stage play Gas Light and the film adaptations released in 1940 and 1944. In the story, a husband attempts to convince his wife and others that she is insane by manipulating small elements of their environment and insisting that she is mistaken, remembering things incorrectly, or delusional when she points out these changes. The original title stems from the dimming of the gas lights in the house that happened when the husband was using the gas lights in the attic while searching for hidden treasure.>>
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Re: APOD: The Helix Nebula from CFHT (2018 Jan 03)

Post by I Say Old Chap » Thu Jan 04, 2018 5:35 pm

bystander wrote:
ellipseshadow wrote:The plural of gas is gases. Gasses is a verb. The correct word to use in this article is gases.
"gasses" is an acceptable variant of the plural form of "gas", especially in British spelling.
Roight!