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

[APOD Robot]

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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[Boomer12k]

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.

:---[===] *

[ta152h0]

https://www.youtube.com/watch?v=7IjgZGhHrYY

[Ann]

It sure is GREEN.

Click to view full size image

[neufer]

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.

[b][color=#0000FF]Closer view of knots in The Helix Nebula.[/color][/b]

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<<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′.>>

[ellipseshadow]

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

[geckzilla]

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

[bystander]

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.

[neufer]

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.

<<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.>>

[I Say Old Chap]

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!