APOD: Horsehead: A Wider View (2018 Mar 09)

Comments and questions about the APOD on the main view screen.
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APOD: Horsehead: A Wider View (2018 Mar 09)

Post by APOD Robot » Fri Mar 09, 2018 5:11 am

[img]https://apod.nasa.gov/apod/calendar/S_180309.jpg[/img] Horsehead: A Wider View

Explanation: Combined image data from the massive, ground-based VISTA telescope and the Hubble Space Telescope was used to create this wide perspective of the interstellar landscape surrounding the famous Horsehead Nebula. Captured at near-infrared wavelengths, the region's dusty molecular cloud sprawls across the scene that covers an angle about two-thirds the size of the Full Moon on the sky. Left to right the frame spans just over 10 light-years at the Horsehead's estimated distance of 1,600 light-years. Also known as Barnard 33, the still recognizable Horsehead Nebula stands at the upper right, the near-infrared glow of a dusty pillar topped with newborn stars. Below and left, the bright reflection nebula NGC 2023 is itself the illuminated environs of a hot young star. Obscuring clouds below the base of the Horsehead and on the outskirts of NGC 2023 show the tell-tale far red emission of energetic jets, known as Herbig-Haro objects, also associated with newborn stars.

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Ann
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Re: APOD: Horsehead: A Wider View (2018 Mar 09)

Post by Ann » Fri Mar 09, 2018 10:14 am

I'm a bit tired of pictures of the Horsehead Nebula, but this one is refreshingly different. This region looks good in infrared light. The combination of visible light and infrared light looks good, too. Fascinating structures! Nice colors!

It's a fine APOD! :D

Ann
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Fisherwood

Re: APOD: Horsehead: A Wider View (2018 Mar 09)

Post by Fisherwood » Fri Mar 09, 2018 1:54 pm

First I thought: That's not the horsehead! Amazing the difference a different set of light wavelengths make!
Beautiful contrast and detail in the emissions below (in this picture)...

Well done! Great variation on the common views of the HH!

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Re: APOD: Horsehead: A Wider View (2018 Mar 09)

Post by neufer » Fri Mar 09, 2018 2:04 pm

https://en.wikipedia.org/wiki/Jar_Jar_Binks wrote:

<<Jar Jar Binks is a major character in Star Wars: Episode I – The Phantom Menace, he also has a smaller role in Episode II: Attack of the Clones, and a one-line cameo in Episode III: Revenge of the Sith, as well as a role in the television series Star Wars: The Clone Wars. Jar Jar's primary role in Episode I was to provide comic relief for the audience. Upon the movie's release, he was met with an overwhelmingly negative reception from both critics and audiences, and is today considered one of the most hated characters in not just Star Wars, but the history of film overall.

Bruce Handy of Vanity Fair wrote that "Jar Jar has come to symbolize what many fans see as the faults of the prequel trilogy: characters no one much cares about; a sense of humor geared toward the youngest conceivable audience members; an over-reliance on computer graphics; and story lines devoted to the kinds of convoluted political machinations which wouldn’t have been out of place in adaptations of I, Claudius or The Rise and Fall of the Third Reich, but which fit less snugly in films with characters like Jar Jar Binks." The character was also lampooned on an episode of the television show South Park entitled "Jakovasaurs", in The Fairly OddParents (Episode: "Abra-Catastrophe!"), The Simpsons (Episode: "Co-Dependent's Day"), as well as the parody Star Wars episodes of Robot Chicken, in which Best reprised the role in voice-over form.

Star Wars creator George Lucas stated that he feels there is a section of the fanbase who get upset with aspects of Star Wars because "the movies are for children but they don't want to admit that... There is a small group of fans that do not like comic sidekicks. They want the films to be tough like The Terminator, and they get very upset and opinionated about anything that has anything to do with being childlike.">>
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Re: APOD: Horsehead: A Wider View (2018 Mar 09)

Post by MarkBour » Fri Mar 09, 2018 5:11 pm

neufer wrote:
Fri Mar 09, 2018 2:04 pm
I see the excellent resemblance. And maybe Jar Jar's hand is even visible in the foreground.

Looking at this magnificent molecular cloud reminds me of the discussion about the hole in NGC1999 in the APOD of 2 days ago when you challenged my thinking about the possible flow of gas there. The term "gas" in our earthly context refers to a state of matter that will have a certain amount of pressure and will expand to fill empty spaces. I realize that the counterpart in an image such as this is so rarefied and so vast that it may not behave that way on any human time scale. And I gather from looking at pillars of such gas that its motions, when they can be detected, may be the opposite of my first intuition (the Hubble "Pillars of Creation" apparently are not billowing outward, but are being carved away).

But, would you agree that even at such scales, there is still a notion of pressure? A statistical drive to spread out, which is countered by gravitational attraction? As I look at an image such as today's APOD, doesn't it indicate that there are some flows in the material of the cloud? More clearly, when a bow shock forms, it indicates that a star is moving through the cloud. After such a star passes, there is turbulent flow of the gas behind it, right? Has somebody already studied this question and determined any of the dynamics of molecular clouds over long time scales?
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Re: APOD: Horsehead: A Wider View (2018 Mar 09)

Post by neufer » Fri Mar 09, 2018 5:31 pm

MarkBour wrote:
Fri Mar 09, 2018 5:11 pm

Looking at this magnificent molecular cloud reminds me of the discussion about the hole in NGC1999 in the APOD of 2 days ago when you challenged my thinking about the possible flow of gas there. The term "gas" in our earthly context refers to a state of matter that will have a certain amount of pressure and will expand to fill empty spaces. I realize that the counterpart in an image such as this is so rarefied and so vast that it may not behave that way on any human time scale. And I gather from looking at pillars of such gas that its motions, when they can be detected, may be the opposite of my first intuition (the Hubble "Pillars of Creation" apparently are not billowing outward, but are being carved away).

But, would you agree that even at such scales, there is still a notion of pressure? A statistical drive to spread out, which is countered by gravitational attraction? As I look at an image such as today's APOD, doesn't it indicate that there are some flows in the material of the cloud? More clearly, when a bow shock forms, it indicates that a star is moving through the cloud. After such a star passes, there is turbulent flow of the gas behind it, right? Has somebody already studied this question and determined any of the dynamics of molecular clouds over long time scales?
There certainly are gas pressures & corresponding shock waves
with gas particle mean free paths measured in AUs (<< a parsec).

However, gas particle & sound wave velocities are primarily dependent upon temperature and
correspond to gas & sound wave velocities we are familiar with : ~ 300 m/s ~ a millionth the speed of light.

And those dust particles that constitute NGC1999 are like cast out
boulders plowing through most any built up concentration of stalled gas.
Art Neuendorffer

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Re: APOD: Horsehead: A Wider View (2018 Mar 09)

Post by Strangerbarry » Fri Mar 09, 2018 6:40 pm

I love the illuminated cavity near the lower left corner. I wonder what the view of the night sky would be from a planet orbiting a star inside that space surrounded by all of that illuminated dust !

The most disappointing thing about the universe is that you and everyone you will ever know will only ever get to see the universe from a single common vantage point.

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Re: APOD: Horsehead: A Wider View (2018 Mar 09)

Post by Chris Peterson » Fri Mar 09, 2018 7:08 pm

Strangerbarry wrote:
Fri Mar 09, 2018 6:40 pm
I love the illuminated cavity near the lower left corner. I wonder what the view of the night sky would be from a planet orbiting a star inside that space surrounded by all of that illuminated dust !
To human eyes, the sky would appear faintly gray, similar to how we see the Milky Way, which would mean fewer distinct stars would be visible (but probably a handful of very bright ones). It would be a less interesting sky than our own.
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neufer
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Re: APOD: Horsehead: A Wider View (2018 Mar 09)

Post by neufer » Fri Mar 09, 2018 7:25 pm

Strangerbarry wrote:
Fri Mar 09, 2018 6:40 pm

The most disappointing thing about the universe is that you
and everyone you will ever know will only ever get to see the universe from a single common vantage point.
The most disappointing thing about the universe is that: Pickering
& Williamina Fleming didn't live long enough to see the perspective of today's APOD.
https://en.wikipedia.org/wiki/Horsehead_Nebula wrote:
<<The Horsehead Nebula (also known as Barnard 33) is a dark nebula in the constellation Orion. The nebula is located just to the south of the star Alnitak, which is farthest east on Orion's Belt, and is part of the much larger Orion Molecular Cloud Complex. The nebula was first recorded in 1888 by Scottish astronomer Williamina Fleming on photographic plate B2312 taken at the Harvard College Observatory.>>
Art Neuendorffer

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Re: APOD: Horsehead: A Wider View (2018 Mar 09)

Post by MarkBour » Fri Mar 09, 2018 7:43 pm

neufer wrote:
Fri Mar 09, 2018 5:31 pm
There certainly are gas pressures & corresponding shock waves
with gas particle mean free paths measured in AUs (<< a parsec).

However, gas particle & sound wave velocities are primarily dependent upon temperature and
correspond to gas & sound wave velocities we are familiar with : ~ 300 m/s ~ a millionth the speed of light.

And those dust particles that constitute NGC1999 are like cast out
boulders plowing through most any built up concentration of stalled gas.
Okay, it sounds to me like you're actually agreeing that a cloud of gas could fill in an empty hole that was a light year in diameter in a time somewhere on the order of a million years. Is it unreasonable to think that the hole was punched in the cloud a few million years ago? But you also keep reminding me of the dust, which I keep ignoring. Is the dust the dominantly visible portion of the reflection nebula? (Apologies to all for dragging this discussion into a second, though related, APOD discussion thread.)
Mark Goldfain

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Re: APOD: Horsehead: A Wider View (2018 Mar 09)

Post by neufer » Fri Mar 09, 2018 8:23 pm

MarkBour wrote:
Fri Mar 09, 2018 7:43 pm

Is the dust the dominantly visible portion of the reflection nebula?
https://en.wikipedia.org/wiki/Reflection_nebula wrote:
<<In astronomy, reflection nebulae are clouds of interstellar dust which might reflect the light of a nearby star or stars. The energy from the nearby stars is insufficient to ionize the gas of the nebula to create an emission nebula, but is enough to give sufficient scattering to make the dust visible. Thus, the frequency spectrum shown by reflection nebulae is similar to that of the illuminating stars. Among the microscopic particles responsible for the scattering are carbon compounds (e. g. diamond dust) and compounds of other elements such as iron and nickel. The latter two are often aligned with the galactic magnetic field and cause the scattered light to be slightly polarized.>>
Art Neuendorffer