APOD: The Helix Nebula in Hydrogen and Oxygen (2019 Feb 13)

[APOD Robot]

The Helix Nebula in Hydrogen and Oxygen

Explanation: Is the Helix Nebula looking at you? No, not in any biological sense, but it does look quite like an eye. The Helix Nebula is so named because it also appears that you are looking down the axis of a helix. In actuality, it is now understood to have a surprisingly complex geometry, including radial filaments and extended outer loops. The Helix Nebula (aka NGC 7293) 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 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 featured picture, taken in the light emitted by oxygen (shown in blue) and hydrogen (shown in red), was created from 74 hours of exposure over three months from a small telescope in a backyard of suburban Melbourne, Australia. A close-up of the inner edge of the Helix Nebula shows complex gas knots of unknown origin.

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[orin stepanek]

Just look me in the eye! Actually; a great photo of a stellar's demise!

[Cousin Ricky]

Just look me in the eye! Actually; a great photo of a stellar's demise!

The world is so exquisite, with so much love and moral depth, that there is no reason to deceive ourselves with pretty stories [the afterlife] for which there’s little good evidence. Far better, it seems to me, in our vulnerability, is to look death in the eye and to be grateful every day for the brief but magnificent opportunity that life provides. —Carl Sagan, “In the Valley of the Shadow,” Parade, March 10, 1996 [emphasis mine]

[Ann]

APOD Robot wrote:

A close-up of the inner edge of the Helix Nebula shows complex gas knots of unknown origin.

To me as an amateur, the gas knots at the inner edge of the Helix Nebula seem straightforward enough. They would be at least somewhat similar to the "Pillars of Creation" in the Eagle Nebula, and they would be caused by a related phenomenon: The strong wind and energetic photons produced by extremely hot stars, that eat away at the edge of a dusty and gaseous nebula of some sort.

Ann

[neufer]

APOD Robot wrote:

A close-up of the inner edge of the Helix Nebula shows complex gas knots of unknown origin.

To me as an amateur, the gas knots at the inner edge of the Helix Nebula seem straightforward enough. They would be at least somewhat similar to the "Pillars of Creation" in the Eagle Nebula, and they would be caused by a related phenomenon: The strong wind and energetic photons produced by extremely hot stars, that eat away at the edge of a dusty and gaseous nebula of some sort.

• But a dusty and gaseous nebula of WHAT sort
  
  And why so thin & straight with knots all along?
  
  Nancy Pelosi: “He's already backed off of the cement – now he's down to,
  I think, a beaded curtain or something, I'm not sure where he is,”

Outer gaseous layers represented in blues and greens

---

This infrared image from NASA's Spitzer Space Telescope shows the Helix Nebula, a cosmic starlet often photographed by amateur astronomers for its vivid colors and eerie resemblance to a giant eye. Planetary nebulae are the remains of stars that once looked a lot like our sun. When sun-like stars die, they puff out their outer gaseous layers. These layers are heated by the hot core of the dead star, called a white dwarf, and shine with infrared and visible colors. Our own sun will blossom into a planetary nebula when it dies in about five billion years. In Spitzer's infrared view of the Helix nebula, the eye looks more like that of a green monster's. Infrared light from the outer gaseous layers is represented in blues and greens. The white dwarf is visible as a tiny white dot in the center of the picture. The red color in the middle of the eye denotes the final layers of gas blown out when the star died. The brighter red circle in the very center is the glow of a dusty disk circling the white dwarf (the disk itself is too small to be resolved). This dust, discovered by Spitzer's infrared heat-seeking vision, was most likely kicked up by comets that survived the death of their star. Before the star died, its comets and possibly planets would have orbited the star in an orderly fashion. But when the star blew off its outer layers, the icy bodies and outer planets would have been tossed about and into each other, resulting in an ongoing cosmic dust storm. Any inner planets in the system would have burned up or been swallowed as their dying star expanded. So far, the Helix nebula is one of only a few dead-star systems in which evidence for comet survivors has been found. This image is made up of data from Spitzer's infrared array camera and multiband imaging photometer. Blue shows infrared light of 3.6 to 4.5 microns; green shows infrared light of 5.8 to 8 microns; and red shows infrared light of 24 microns.

[dmiladinovich]

I am incredibly interested on how this photographer took this with his telescope over 3 months and 74 hours of exposures. Are there any references or materials describing how he did it? This is beautiful.

[juliajoy@comcast.net]

AWESOME! From a backyard telescope, at that. Congratulations on a marvelous image, and thanks for all the time you spent to give it to we who love looking at space and its objects.

[Andy Campbell]

I am incredibly interested on how this photographer took this with his telescope over 3 months and 74 hours of exposures. Are there any references or materials describing how he did it? This is beautiful.

Hi there - I'm the photographer so will attempt to answer : )

The camera is attached to a telescope which in turn rides on a mount that rotates parallel with the earth's core.
Guiding software allows me to leave the shutter open for 30 mins at a time, over several clear nights.
I use a purpose built Astro camera loaded with short bypass wavelength filters that allow only the light emitted by the nebula's individual gases to be captured. The idea is to build up the exposure over many nights to overcome the signal to noise ratio & get a nice clear picture.
As the outer regions of this nebula are so feint, I needed months of clear nights to gather enough data for these to show up clearly!

These sub-exposures are then stacked to create master files for each filter, which are then assigned as R, G & B layers RGB in Photoshop.
The resulting image is then fine tuned in processing to yield the best details & colours.
Short RG&B exposures are taken seperately to capture the natural colours of the stars themselves.

Best results are usually obtained from remote dark sites unaffected by light pollution.
Unfortunately, my suburban backyard is not like this as I live in a city of 5,000,000 people, so everything is just that much more difficult!

Hope that helps!
Cheers

Andy
https://www.facebook.com/AndysAstropix

[Andy Campbell]

AWESOME! From a backyard telescope, at that. Congratulations on a marvelous image, and thanks for all the time you spent to give it to we who love looking at space and its objects.

Thanks very much Julia, you are most welcome - delighted that you enjoyed the image

[MarkBour]

APOD Robot wrote:

A close-up of the inner edge of the Helix Nebula shows complex gas knots of unknown origin.

To me as an amateur, the gas knots at the inner edge of the Helix Nebula seem straightforward enough. They would be at least somewhat similar to the "Pillars of Creation" in the Eagle Nebula, and they would be caused by a related phenomenon: The strong wind and energetic photons produced by extremely hot stars, that eat away at the edge of a dusty and gaseous nebula of some sort.

• But a dusty and gaseous nebula of WHAT sort
  
  And why so thin & straight with knots all along?

I have enjoyed reading a bit about these cometary globules. One nice reference is at: https://iopscience.iop.org/article/10.1 ... /fulltext/ where they examined one at high resolution and found CO and H₂.

This gives me an idea. Most ideas like this that I have will fail, of course:

Imagining that as part of the death of the star it "boiled" most of the planets and moons and some of the outer bodies (if it had a region like our Kuiper belt), then as the later shock blows everything out of the middle of the planetary nebula, there is still enough matter from those bodies to drag through the expanding gas shell, in the manner that Ann described. This is the matter of which that star system's icy and gas giant bodies were formed. In the Helix Nebula, as this material is pushed outward, but lagging behind much of the thinner ejecta, it finally cools again and begins to condense. In short, my hypothesis is that these globules are made in part from the matter that was once in the planets, moons, asteroids, comets (i.e. the planetary disk) that circled the central star. That may just be part of the condensation, perhaps some of the star's matter is in them, too.

Even if I'm wrong, I have a feeling that one way or another, the term "planetary nebula" will eventually become an appropriate name for these structures, moreso than is currently considered to be the case.

[orin stepanek]

Just look me in the eye! Actually; a great photo of a stellar's demise!

The world is so exquisite, with so much love and moral depth, that there is no reason to deceive ourselves with pretty stories [the afterlife] for which there’s little good evidence. Far better, it seems to me, in our vulnerability, is to look death in the eye and to be grateful every day for the brief but magnificent opportunity that life provides. —Carl Sagan, “In the Valley of the Shadow,” Parade, March 10, 1996 [emphasis mine]

I don't want to get into an argument about this, but give DNA a good look! We are not allowed to discuss this!

[dmiladinovich]

I am incredibly interested on how this photographer took this with his telescope over 3 months and 74 hours of exposures. Are there any references or materials describing how he did it? This is beautiful.

Hi there - I'm the photographer so will attempt to answer : )

The camera is attached to a telescope which in turn rides on a mount that rotates parallel with the earth's core.
Guiding software allows me to leave the shutter open for 30 mins at a time, over several clear nights.
I use a purpose built Astro camera loaded with short bypass wavelength filters that allow only the light emitted by the nebula's individual gases to be captured. The idea is to build up the exposure over many nights to overcome the signal to noise ratio & get a nice clear picture.
As the outer regions of this nebula are so feint, I needed months of clear nights to gather enough data for these to show up clearly!

These sub-exposures are then stacked to create master files for each filter, which are then assigned as R, G & B layers RGB in Photoshop.
The resulting image is then fine tuned in processing to yield the best details & colours.
Short RG&B exposures are taken seperately to capture the natural colours of the stars themselves.

Best results are usually obtained from remote dark sites unaffected by light pollution.
Unfortunately, my suburban backyard is not like this as I live in a city of 5,000,000 people, so everything is just that much more difficult!

Hope that helps!
Cheers

Andy
https://www.facebook.com/AndysAstropix

Hi Andy! I feel honored that the photographer replied to my message. You're an inspiration. I have always loved astronomy and photography and have always wanted to learn to take a process photos through a telescope. Thank you for this and thank you APOD for show casing your work!

[neufer]

Click to play embedded YouTube video.