APOD: In the Core of the Carina Nebula (2024 Feb 05)

[APOD Robot]

In the Core of the Carina Nebula

Explanation: What's happening in the core of the Carina Nebula? Stars are forming, dying, and leaving an impressive tapestry of dark dusty filaments. The entire Carina Nebula, cataloged as NGC 3372, spans over 300 light years and lies about 8,500 light-years away in the constellation of Carina. The nebula is composed predominantly of hydrogen gas, which emits the pervasive red and orange glows seen mostly in the center of this highly detailed featured image. The blue glow around the edges is created primarily by a trace amount of glowing oxygen. Young and massive stars located in the nebula's center expel dust when they explode in supernovas. Eta Carinae, the most energetic star in the nebula's center, was one of the brightest stars in the sky in the 1830s, but then faded dramatically.

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[Ann]

I have very little time today, so I'll try to do this quickly...

In the Core of the Carina Nebula Image Credit & Copyright: Carlos Taylor

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A closeup of the central part of the Carina Nebula.

You can see some of the same sights in this Hubble image:

The Mystic Mountain, Trumpler 14, Nessie and Loch Ness in the Carina Nebula. Credit: NASA, ESA, N. Smith (University of California, Berkeley), and The Hubble Heritage Team

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The Mystic Mountain is fun to look at. It is being eroded by Trumpler 14:

The Mystic Mountain. Credit: NASA, ESA, and M. Livio and the Hubble 20th Anniversary Team (STScI)

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Trumpler 14 contains some of the most luminous stars in the galaxy:

Trumpler 14. Credit: NASA & ESA, Jesús Maíz Apellániz

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The real powerhouse in the Carina Nebula is, of course, Eta Carina. This ESO overview shows you Trumpler 14 at center right and Eta Carina (a bright blob) at center left:

The Carina Nebula with Eta Carina and Trumpler 14. Credit: ESO/IDA/Danish 1.5 m/R.Gendler, J-E. Ovaldsen, C. Thöne, and C. Feron.

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Just like the Mystic Mountain, Eta Carina sure looks funny when you take a close look at it:

Eta Carina is a monster star that had a super duper outburst in the 19th century. It blew off at least a Sun's worth of matter that now forms the distinctive Homunculus nebula shape around it. Credit: Hubble, I guess!

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Don't have time to write more now! I'm off!

Ann

[Iksarfighter]

Strange, Paint refuse to open the full res image.

[Case]

What is HOS Foraxx (bottom left corner)?

[johnnydeep]

Strange, Paint refuse to open the full res image.

Worked for me with Paint not complaining at all, but Paint 3D said it was "too big" and conveniently resized it. The full res image is 91 Mega pixels (about 9500x9500), but only 6 MB in file size.

[johnnydeep]

What is HOS Foraxx (bottom left corner)?

I believe HOS is Hydrogen Oxygen and Sulfur (filters?), and Foraxx is apparently a "palate" available in Pixinsight. See this for example:

One of the nice aspects of PixInsight is the many engineers developing scripts, plugins and complex PixelMath expressions. These add-ons can often make life of the hobby astrophotographer a whole lot easier and the output of our work a whole lot better. Recent examples are the AI-based plugins developed by Russell Croman such as BlurXterminator, the Generalised Hyperbolic Stretch tool developed by Mike Cranfield and Dave Payne, and the HOO scripts for OSC images written by Bill Blanshan.

A new script has now been released by Paulyman Astro, that automates the process of creating narrow-band images in Foraxx palette. The Foraxx palette makes use of so-called dynamic narrowband combinations, as published by The Coldest Nights. Compared to Hubble palette images, Foraxx images have their own look with often more bronze-colours in them, and less dominant blues.

The script works for narrowband images from monochrome cameras, as well as OSC cameras with dual-band filters. It requires the stars to be separated from he nebulosity, so star removal is a prerequisite. This is typically a one-click operation using tools such as Starnet2 (free) or StarXTerminator (paid).

Paulyman Astro makes the script available for free. Just add https://foraxxpaletteutility.com/FPU/ to the repositories in PixInsight, run ‘check for updates’ and upon closing of PixInsight, the script will be installed. When installed it can be found under Scripts > Utilities > ForaxxPaletteUtility.

[johnnydeep]

What I really need is an overlay showing where this close-up is in the whole Carina Nebula, and where Eta Carina is!

[pferkul]

What I really need is an overlay showing where this close-up is in the whole Carina Nebula, and where Eta Carina is!

Based on Wikipedia (first attachment), I think it's as indicated by the arrow in the second attachment.

[johnnydeep]

What I really need is an overlay showing where this close-up is in the whole Carina Nebula, and where Eta Carina is!

Based on Wikipedia (first attachment), I think it's as indicated by the arrow in the second attachment.

Thanks. That's it!

[Fatimfsel14]

What does HOS Foraxx refer to (located in the bottom left corner)?

[Chris Peterson]

What is HOS Foraxx (bottom left corner)?

I believe HOS is Hydrogen Oxygen and Sulfur (filters?), and Foraxx is apparently a "palate" available in Pixinsight. See this for example:

More generally, all images are output as a ratio of red, green, and blue because those are the native pixel colors on our displays. "True color" images are also collected through broad red, green, and blue filters, which approximately match our displays. So those are often called RGB images.

Science images (and also ones with a specific aesthetic) are often collected through narrowband (just a few nanometers) filters that are centered on the emission of specific elements. By far the most common filters (and largely the only ones used by amateurs) are H-alpha (singly ionized hydrogen, H II, 656 nm), [O III] (doubly ionized oxygen, 501 nm), and [ S II] (singly ionized sulfur, 672 nm). The tricky bit here is that both the H and S filters are passing deep red light, so there are different ways of deciding what colors they will be assigned to for display.

Common nomenclature is to list the filters in RGB order, so

HOO has H assigned to red, O assigned to green, O assigned to blue (which actually means O is displayed as cyan, G+B).
SHO has S assigned to red, H assigned to green, O assigned to blue. This is usually called the "Hubble palette".
HSO has H assigned to red, S assigned to green, O assigned to blue. Slightly more natural as hydrogen (red) is usually the dominant emission.
HOS has H assigned to red, O assigned to green, S assigned to blue. That's what is used with this image, and likely leads to the closest "true color" representation possible with these three filters.

Beyond this, there are different ways of balancing the weights of the RGB channels to get different visual appearances, and the Foraxx reference is to one of these techniques (but the raw data is still HOS).

And there are even more complex ways of doing things, where individual input channels are mixed across multiple output channels (as with the HOO case above). And sometimes broad and narrow filter data are combined, as well. Very often we'll see the RGB data used to create natural colored stars in an image that is otherwise narrowband (which usually produces weird star colors, like the magenta ones commonly seen in Hubble images).

[johnnydeep]

What is HOS Foraxx (bottom left corner)?

I believe HOS is Hydrogen Oxygen and Sulfur (filters?), and Foraxx is apparently a "palate" available in Pixinsight. See this for example:

More generally, all images are output as a ratio of red, green, and blue because those are the native pixel colors on our displays. "True color" images are also collected through broad red, green, and blue filters, which approximately match our displays. So those are often called RGB images.

Science images (and also ones with a specific aesthetic) are often collected through narrowband (just a few nanometers) filters that are centered on the emission of specific elements. By far the most common filters (and largely the only ones used by amateurs) are H-alpha (singly ionized hydrogen, H II, 656 nm), [O III] (doubly ionized oxygen, 501 nm), and [ S II] (singly ionized sulfur, 672 nm). The tricky bit here is that both the H and S filters are passing deep red light, so there are different ways of deciding what colors they will be assigned to for display.

Common nomenclature is to list the filters in RGB order, so

HOO has H assigned to red, O assigned to green, O assigned to blue (which actually means O is displayed as cyan, G+B).
SHO has S assigned to red, H assigned to green, O assigned to blue. This is usually called the "Hubble palette".
HSO has H assigned to red, S assigned to green, O assigned to blue. Slightly more natural as hydrogen (red) is usually the dominant emission.
HOS has H assigned to red, O assigned to green, S assigned to blue. That's what is used with this image, and likely leads to the closest "true color" representation possible with these three filters.

Beyond this, there are different ways of balancing the weights of the RGB channels to get different visual appearances, and the Foraxx reference is to one of these techniques (but the raw data is still HOS).

And there are even more complex ways of doing things, where individual input channels are mixed across multiple output channels (as with the HOO case above). And sometimes broad and narrow filter data are combined, as well. Very often we'll see the RGB data used to create natural colored stars in an image that is otherwise narrowband (which usually produces weird star colors, like the magenta ones commonly seen in Hubble images).

Thanks! There's a lot of info to unpack in those paragraphs. Much appreciated.

Now, a more basic question: I realized that I don't really know how a filter works. So, light is collected by a some lens and mirror combination, and eventually the light/photons hit a CCD detector array. At what point does a filter come into play? I think I've seen amateur telescopes with filters in front of the objective lens of a refractor. But that clearly can't be how filters work on Hubble since that would require massive filters and some large mechanical means of putting them in place. So, do the filters get interposed somehow right before the light hits the CCD array?

And finally, are filters just some sort of tinted film on the surface of (or embedded within) a thin piece of glass, or can they be changed electronically? (I'm thinking of those electrical window shading glass panels in high-end houses and office buildings.)

[Chris Peterson]

I believe HOS is Hydrogen Oxygen and Sulfur (filters?), and Foraxx is apparently a "palate" available in Pixinsight. See this for example:

More generally, all images are output as a ratio of red, green, and blue because those are the native pixel colors on our displays. "True color" images are also collected through broad red, green, and blue filters, which approximately match our displays. So those are often called RGB images.

Science images (and also ones with a specific aesthetic) are often collected through narrowband (just a few nanometers) filters that are centered on the emission of specific elements. By far the most common filters (and largely the only ones used by amateurs) are H-alpha (singly ionized hydrogen, H II, 656 nm), [O III] (doubly ionized oxygen, 501 nm), and [ S II] (singly ionized sulfur, 672 nm). The tricky bit here is that both the H and S filters are passing deep red light, so there are different ways of deciding what colors they will be assigned to for display.

Common nomenclature is to list the filters in RGB order, so

HOO has H assigned to red, O assigned to green, O assigned to blue (which actually means O is displayed as cyan, G+B).
SHO has S assigned to red, H assigned to green, O assigned to blue. This is usually called the "Hubble palette".
HSO has H assigned to red, S assigned to green, O assigned to blue. Slightly more natural as hydrogen (red) is usually the dominant emission.
HOS has H assigned to red, O assigned to green, S assigned to blue. That's what is used with this image, and likely leads to the closest "true color" representation possible with these three filters.

Beyond this, there are different ways of balancing the weights of the RGB channels to get different visual appearances, and the Foraxx reference is to one of these techniques (but the raw data is still HOS).

And there are even more complex ways of doing things, where individual input channels are mixed across multiple output channels (as with the HOO case above). And sometimes broad and narrow filter data are combined, as well. Very often we'll see the RGB data used to create natural colored stars in an image that is otherwise narrowband (which usually produces weird star colors, like the magenta ones commonly seen in Hubble images).

Thanks! There's a lot of info to unpack in those paragraphs. Much appreciated.

Now, a more basic question: I realized that I don't really know how a filter works. So, light is collected by a some lens and mirror combination, and eventually the light/photons hit a CCD detector array. At what point does a filter come into play? I think I've seen amateur telescopes with filters in front of the objective lens of a refractor. But that clearly can't be how filters work on Hubble since that would require massive filters and some large mechanical means of putting them in place. So, do the filters get interposed somehow right before the light hits the CCD array?

And finally, are filters just some sort of tinted film on the surface of (or embedded within) a thin piece of glass, or can they be changed electronically? (I'm thinking of those electrical window shading glass panels in high-end houses and office buildings.)

The only filters that people place at the telescope aperture are solar filters, because you have to attenuate the light before it gets focused or you'll melt stuff inside the telescope! And those are just aluminized glass or plastic that passes all wavelengths. Pretty much the same material that eclipse glasses are made of.

Otherwise, filters are always in the optical path in front of the camera. Usually the last optics before the sensor (other than windows in the camera body itself and on the sensor chip). They tend to be quite expensive, so you want to use as small of ones as possible... normally just a little larger than the sensor diagonal.

Broadband filters (for amateurs that means RGB) have widths around 100 nm, and are usually dye-based. Basically, colored glass. They are relatively inexpensive. Narrowband filters are usually only 3-6 nm wide, and you can't do that with a colored dye. Those are interference filters, that are made by depositing many thin layers of optical material having different indices of refraction, spaced such that only one wavelength is constructively interefered with, and the rest destructively. This is combined with a broader colored filter to isolate just the wavelength of interest and not multiples of it. You can imagine that the process involved in making such filters is tricky... and the prices reflect that. (A good one can easily set you back $300.)

There are no electrically tunable filters like you describe (but some narrowband filters, in particular those designed to look at solar emissions, can be electrically tuned over a very narrow range. Those filters have widths less than 1 nm and cost thousands of dollars.)

[johnnydeep]

More generally, all images are output as a ratio of red, green, and blue because those are the native pixel colors on our displays. "True color" images are also collected through broad red, green, and blue filters, which approximately match our displays. So those are often called RGB images.

Science images (and also ones with a specific aesthetic) are often collected through narrowband (just a few nanometers) filters that are centered on the emission of specific elements. By far the most common filters (and largely the only ones used by amateurs) are H-alpha (singly ionized hydrogen, H II, 656 nm), [O III] (doubly ionized oxygen, 501 nm), and [ S II] (singly ionized sulfur, 672 nm). The tricky bit here is that both the H and S filters are passing deep red light, so there are different ways of deciding what colors they will be assigned to for display.

Common nomenclature is to list the filters in RGB order, so

HOO has H assigned to red, O assigned to green, O assigned to blue (which actually means O is displayed as cyan, G+B).
SHO has S assigned to red, H assigned to green, O assigned to blue. This is usually called the "Hubble palette".
HSO has H assigned to red, S assigned to green, O assigned to blue. Slightly more natural as hydrogen (red) is usually the dominant emission.
HOS has H assigned to red, O assigned to green, S assigned to blue. That's what is used with this image, and likely leads to the closest "true color" representation possible with these three filters.

Beyond this, there are different ways of balancing the weights of the RGB channels to get different visual appearances, and the Foraxx reference is to one of these techniques (but the raw data is still HOS).

And there are even more complex ways of doing things, where individual input channels are mixed across multiple output channels (as with the HOO case above). And sometimes broad and narrow filter data are combined, as well. Very often we'll see the RGB data used to create natural colored stars in an image that is otherwise narrowband (which usually produces weird star colors, like the magenta ones commonly seen in Hubble images).

Thanks! There's a lot of info to unpack in those paragraphs. Much appreciated.

Now, a more basic question: I realized that I don't really know how a filter works. So, light is collected by a some lens and mirror combination, and eventually the light/photons hit a CCD detector array. At what point does a filter come into play? I think I've seen amateur telescopes with filters in front of the objective lens of a refractor. But that clearly can't be how filters work on Hubble since that would require massive filters and some large mechanical means of putting them in place. So, do the filters get interposed somehow right before the light hits the CCD array?

And finally, are filters just some sort of tinted film on the surface of (or embedded within) a thin piece of glass, or can they be changed electronically? (I'm thinking of those electrical window shading glass panels in high-end houses and office buildings.)

The only filters that people place at the telescope aperture are solar filters, because you have to attenuate the light before it gets focused or you'll melt stuff inside the telescope! And those are just aluminized glass or plastic that passes all wavelengths. Pretty much the same material that eclipse glasses are made of.

Otherwise, filters are always in the optical path in front of the camera. Usually the last optics before the sensor (other than windows in the camera body itself and on the sensor chip). They tend to be quite expensive, so you want to use as small of ones as possible... normally just a little larger than the sensor diagonal.

Broadband filters (for amateurs that means RGB) have widths around 100 nm, and are usually dye-based. Basically, colored glass. They are relatively inexpensive. Narrowband filters are usually only 3-6 nm wide, and you can't do that with a colored dye. Those are interference filters, that are made by depositing many thin layers of optical material having different indices of refraction, spaced such that only one wavelength is constructively interefered with, and the rest destructively. This is combined with a broader colored filter to isolate just the wavelength of interest and not multiples of it. You can imagine that the process involved in making such filters is tricky... and the prices reflect that. (A good one can easily set you back $300.)

There are no electrically tunable filters like you describe (but some narrowband filters, in particular those designed to look at solar emissions, can be electrically tuned over a very narrow range. Those filters have widths less than 1 nm and cost thousands of dollars.)

Thanks! You are truly a cornucopia of knowledge.