APOD: A Halo for NGC 6164 (2014 May 22)

Comments and questions about the APOD on the main view screen.

APOD: A Halo for NGC 6164 (2014 May 22)

Postby APOD Robot » Thu May 22, 2014 4:07 am

Image A Halo for NGC 6164

Explanation: Beautiful emission nebula NGC 6164 was created by a rare, hot, luminous O-type star, some 40 times as massive as the Sun. Seen at the center of the cosmic cloud, the star is a mere 3 to 4 million years old. In another three to four million years the massive star will end its life in a supernova explosion. Spanning around 4 light-years, the nebula itself has a bipolar symmetry. That makes it similar in appearance to more common and familiar planetary nebulae - the gaseous shrouds surrounding dying sun-like stars. Also like many planetary nebulae, NGC 6164 has been found to have an extensive, faint halo, revealed in this deep telescopic image of the region. Expanding into the surrounding interstellar medium, the material in the halo is likely from an earlier active phase of the O star. The gorgeous skyscape is a composite of extensive narrow-band image data, highlighting glowing atomic hydrogen gas in red and oxygen in blue hues, with broad-band data for the surrounding starfield. NGC 6164 is 4,200 light-years away in the right-angled southern constellation of Norma.

<< Previous APOD This Day in APOD Next APOD >>
User avatar
APOD Robot
Otto Posterman
 
Posts: 1830
Joined: Fri Dec 04, 2009 3:27 am

Re: APOD: A Halo for NGC 6164 (2014 May 22)

Postby Boomer12k » Thu May 22, 2014 10:09 am

Birth PANGS??? TEETHING????

Young and CRANKY....

:---[===] *
Boomer12k
:---[===] *
 
Posts: 1075
Joined: Sun Apr 22, 2007 12:07 am

Re: APOD: A Halo for NGC 6164 (2014 May 22)

Postby Lithopsian » Thu May 22, 2014 10:39 am

The most recent research suggests a 50-60 solar mass star at the centre of this nebula, with a temperature around 41,000K and luminosity around 630,000 times the sun. It is unusual in several respects, with strong x-ray radiation and magnetic field. The bipolar nebula in this image is not understood. Such nebulae are usually due to ejection along the rotational axis of the star, but this doesn't appear to be the case here. There is a much larger nearly spherical bubble around the star, de simply to the powerful winds from such hot stars.
Lithopsian
 

Re: APOD: A Halo for NGC 6164 (2014 May 22)

Postby BDanielMayfield » Thu May 22, 2014 11:08 am

Lithopsian wrote:The most recent research suggests a 50-60 solar mass star at the centre of this nebula, with a temperature around 41,000K and luminosity around 630,000 times the sun. It is unusual in several respects, with strong x-ray radiation and magnetic field. The bipolar nebula in this image is not understood. Such nebulae are usually due to ejection along the rotational axis of the star, but this doesn't appear to be the case here. There is a much larger nearly spherical bubble around the star, de simply to the powerful winds from such hot stars.

That's interesting. Can you kindly provide a reference to "the most recent research"?
"Happy are the peaceable ... "
BDanielMayfield
Don't bring me down
 
Posts: 808
Joined: Thu Aug 02, 2012 11:24 am
Location: South Texas
AKA: Bruce


Re: APOD: A Halo for NGC 6164 (2014 May 22)

Postby Psnarf » Thu May 22, 2014 3:23 pm

What is the radius of the faint halo cloud? More than eight light years? The referenced article in the referenced APOD link,
http://adsabs.harvard.edu/cgi-bin/nph-d ... =AST&high=
describes distances from the star in parsecs. The overall size is 20 X 15 arc minutes. I don't know how to translate that into light years.

I'm amazed that the young hydrogen-oxygen bubble glows so far away from the source of the interstellar wind.
User avatar
Psnarf
Science Officer
 
Posts: 272
Joined: Fri Feb 26, 2010 6:19 pm

Re: APOD: A Halo for NGC 6164 (2014 May 22)

Postby Chris Peterson » Thu May 22, 2014 3:38 pm

Psnarf wrote:What is the radius of the faint halo cloud? More than eight light years? The referenced article in the referenced APOD link,
http://adsabs.harvard.edu/cgi-bin/nph-d ... =AST&high=
describes distances from the star in parsecs. The overall size is 20 X 15 arc minutes. I don't know how to translate that into light years.

I'm amazed that the young hydrogen-oxygen bubble glows so far away from the source of the interstellar wind.


It shows a bubbly structure with overall dimensions of 20 X 15 arc min with the major axis aligned with that of NGC 6164-65. For a distance of ~ 1 kpc (see below) this corresponds to 6 X 4.5 pc.

That's a very old paper, so I'd be skeptical of the values they are using for distance. All they're saying is that assuming a distance of 1 kpc, the angular extent of the object corresponds to a physical size of 6 x 4.5 pc. A parsec is 3.3 light years. So a cloud around 15-20 light years in diameter.
Chris

*****************************************
Chris L Peterson
Cloudbait Observatory
http://www.cloudbait.com
User avatar
Chris Peterson
Abominable Snowman
 
Posts: 9422
Joined: Wed Jan 31, 2007 11:13 pm
Location: Colorado, USA

Re: APOD: A Halo for NGC 6164 (2014 May 22)

Postby LocalColor » Thu May 22, 2014 4:42 pm

This image reminds me of what Carl Sagan said many years ago - "We are made of starstuff.”
User avatar
LocalColor
Science Officer
 
Posts: 219
Joined: Sat Mar 31, 2012 9:11 pm
Location: Central Idaho, USA

Re: APOD: A Halo for NGC 6164 (2014 May 22)

Postby starsurfer » Thu May 22, 2014 5:02 pm

Psnarf wrote:What is the radius of the faint halo cloud? More than eight light years? The referenced article in the referenced APOD link,
http://adsabs.harvard.edu/cgi-bin/nph-d ... =AST&high=
describes distances from the star in parsecs. The overall size is 20 X 15 arc minutes. I don't know how to translate that into light years.

I'm amazed that the young hydrogen-oxygen bubble glows so far away from the source of the interstellar wind.

I think that part of the ionization for the outer part is the energy generated by the gas colliding into the surrounding interstellar medium. I'm amazed that supernova remants can continue glowing for thousands of years!!
starsurfer
Commander
 
Posts: 996
Joined: Thu Mar 15, 2012 7:25 pm

Re: APOD: A Halo for NGC 6164 (2014 May 22)

Postby Chris Peterson » Thu May 22, 2014 5:07 pm

starsurfer wrote:I think that part of the ionization for the outer part is the energy generated by the gas colliding into the surrounding interstellar medium. I'm amazed that supernova remants can continue glowing for thousands of years!!

I'm not sure you're suggesting it, but to be clear, this isn't a supernova remnant.

That said, maybe you should be surprised that material of several solar masses can be heated to the point that it emits as much energy as an entire galaxy, and yet only glow for a few thousand years!
Chris

*****************************************
Chris L Peterson
Cloudbait Observatory
http://www.cloudbait.com
User avatar
Chris Peterson
Abominable Snowman
 
Posts: 9422
Joined: Wed Jan 31, 2007 11:13 pm
Location: Colorado, USA

Re: APOD: A Halo for NGC 6164 (2014 May 22)

Postby Beyond » Thu May 22, 2014 5:52 pm

Chris Peterson wrote:That said, maybe you should be surprised that material of several solar masses can be heated to the point that it emits as much energy as an entire galaxy, and yet only glow for a few thousand years!

Reminds me of when I was a kid and put 2-cell flashlight bulbs in a 5-cell flashlight. Wow! Were they bright! But they only lasted about 30 seconds or so.
To find the Truth, you must go Beyond.
User avatar
Beyond
500 Gigaderps
 
Posts: 6488
Joined: Tue Aug 04, 2009 11:09 am
Location: BEYONDER LAND

Re: APOD: A Halo for NGC 6164 (2014 May 22)

Postby Ann » Fri May 23, 2014 5:23 am

When I first saw this APOD, I jumped to the conclusion that the object in it was a planetary nebula. That gave me pause. My initial reaction was that I wouldn't comment on it, because the colors of planetary nebulas weird me out. I guess that their colors aren't that strange, but the wild mapped hues of various narrowband pictures of planetary nebulas freak me out, because I can't image what the colors "really" are. I'm lost.

Well, this isn't a planetary nebula, and I have no problems forming a mental picture of the "true" colors here. Interestingly though, the shape of this object certainly resembles the shape of a planetary nebula. Even the outer halo is often seen in planetaries. The processes that form a planetary nebula must be somewhat similar to the processes that created NGC 6164.

The big difference is in the central star of these nebulas. In a planetary nebula, the central star is small and lightweight, and it can only explode if a nearby companion dumps enough matter on it. But the central star of NGC 6164 is a massive O star, which will almost certainly explode all of its own.

Ann
Color Commentator
User avatar
Ann
4725 Å
 
Posts: 5741
Joined: Sat May 29, 2010 5:33 am

Re: APOD: A Halo for NGC 6164 (2014 May 22)

Postby geckzilla » Fri May 23, 2014 11:17 am

Ann wrote:Well, this isn't a planetary nebula, and I have no problems forming a mental picture of the "true" colors here.

This object isn't especially from a planetary nebulas different as far as colors go. Many planetary nebulas are also imaged in H-alpha and OIII. The blue outer shell for NGC 6164 is nearly invisible without narrowband data. Congratulations, you just tricked yourself into overcoming your bias against narrowband.
Just call me "geck" because "zilla" is like a last name.
User avatar
geckzilla
Ocular Digitator
 
Posts: 5712
Joined: Wed Sep 12, 2007 12:42 pm
Location: Fresh Meadows, NY

Re: APOD: A Halo for NGC 6164 (2014 May 22)

Postby DavidLeodis » Fri May 23, 2014 1:01 pm

It's a fascinating and intriguing image. :)

The halo has three distinct areas that look as if they might have resulted from having been blown away from the nebula. I am wondering why there is not a fourth distinct halo area that I would have thought there might be?
User avatar
DavidLeodis
Perceptatron
 
Posts: 811
Joined: Mon May 01, 2006 1:00 pm

Re: APOD: A Halo for NGC 6164 (2014 May 22)

Postby Ann » Fri May 23, 2014 8:22 pm

geckzilla wrote:
Ann wrote:Well, this isn't a planetary nebula, and I have no problems forming a mental picture of the "true" colors here.

This object isn't especially from a planetary nebulas different as far as colors go. Many planetary nebulas are also imaged in H-alpha and OIII. The blue outer shell for NGC 6164 is nearly invisible without narrowband data. Congratulations, you just tricked yourself into overcoming your bias against narrowband.


NGC 6164 isn't hard to understand, colorwise. There is a bright blue O star in the middle, surrounded by two lobes of ordinary red Ha emission. There is an extremely faint outer halo that I admittedly can't quite imagine, since I'm generally unsure about the true color of OIII light. But then again, the outer halo is so faint that I'm quite okay about not being able to truly imagine it.

Planetary nebulas are so much more confusing. There is no way I can imagine the true colors of NGC 7072, for example.

Ann
Color Commentator
User avatar
Ann
4725 Å
 
Posts: 5741
Joined: Sat May 29, 2010 5:33 am

Re: APOD: A Halo for NGC 6164 (2014 May 22)

Postby geckzilla » Fri May 23, 2014 9:36 pm

It's just light. You don't have to imagine anything about it if there's an image right there to look at. Without narrowband they are just bland clouds.
Just call me "geck" because "zilla" is like a last name.
User avatar
geckzilla
Ocular Digitator
 
Posts: 5712
Joined: Wed Sep 12, 2007 12:42 pm
Location: Fresh Meadows, NY

Re: APOD: A Halo for NGC 6164 (2014 May 22)

Postby Ann » Sat May 24, 2014 4:29 am

geckzilla wrote:It's just light. You don't have to imagine anything about it if there's an image right there to look at. Without narrowband they are just bland clouds.


Well, that's me. Mapped color, when I can't "translate" it into true color, makes the object "unrelatable" to me. And then I can't say much about it.

As for "them" being just bland clouds without narrowband, they would at least be clouds of certain colors. If I knew what those colors are, then I could start "translating" the narrowband image into something approximately "true optical colors" and "relate" to it.

Ann
Color Commentator
User avatar
Ann
4725 Å
 
Posts: 5741
Joined: Sat May 29, 2010 5:33 am

Re: APOD: A Halo for NGC 6164 (2014 May 22)

Postby geckzilla » Sat May 24, 2014 5:28 am

Maybe try taking things literally and use less quote marks.
Just call me "geck" because "zilla" is like a last name.
User avatar
geckzilla
Ocular Digitator
 
Posts: 5712
Joined: Wed Sep 12, 2007 12:42 pm
Location: Fresh Meadows, NY

Re: APOD: A Halo for NGC 6164 (2014 May 22)

Postby Ann » Sat May 24, 2014 5:44 am

geckzilla wrote:Maybe try taking things literally and use less quote marks.


Okay. :wink:

It's just light. You don't have to imagine anything about it if there's an image right there to look at. Without narrowband they are just bland clouds.


Well, that's me. Mapped color, when I can't translate it into true color, makes the object unrelatable to me. And then I can't say much about it.

As for them being just bland clouds without narrowband, they would at least be clouds of certain colors. If I knew what those colors are, then I could start translating the narrowband image into something approximately true optical colors and relate to it.

Ann
Color Commentator
User avatar
Ann
4725 Å
 
Posts: 5741
Joined: Sat May 29, 2010 5:33 am

Re: APOD: A Halo for NGC 6164 (2014 May 22)

Postby geckzilla » Sat May 24, 2014 2:24 pm

It is a bit like looking at an x-ray of your body and not understanding bones because bones do not look exactly like they do in the x-ray picture to your eyes. They look exactly like that, though. The x-ray film has done all the translating you need already.
Just call me "geck" because "zilla" is like a last name.
User avatar
geckzilla
Ocular Digitator
 
Posts: 5712
Joined: Wed Sep 12, 2007 12:42 pm
Location: Fresh Meadows, NY

Re: APOD: A Halo for NGC 6164 (2014 May 22)

Postby Chris Peterson » Sat May 24, 2014 6:02 pm

Ann wrote:Well, that's me. Mapped color, when I can't "translate" it into true color, makes the object "unrelatable" to me.

There's no such thing as true color for dim astronomical objects. And you've never seen an image of an astronomical object that wasn't mapped color. So you'll need to be a good deal more precise in defining your terms if you want to be clearly understood.
Chris

*****************************************
Chris L Peterson
Cloudbait Observatory
http://www.cloudbait.com
User avatar
Chris Peterson
Abominable Snowman
 
Posts: 9422
Joined: Wed Jan 31, 2007 11:13 pm
Location: Colorado, USA

Re: APOD: A Halo for NGC 6164 (2014 May 22)

Postby Ann » Sat May 24, 2014 7:06 pm

Chris Peterson wrote:
Ann wrote:Well, that's me. Mapped color, when I can't "translate" it into true color, makes the object "unrelatable" to me.

There's no such thing as true color for dim astronomical objects. And you've never seen an image of an astronomical object that wasn't mapped color. So you'll need to be a good deal more precise in defining your terms if you want to be clearly understood.


Obviously, I mean the sort of color that can be seen by the "RGB" receptors in the human eye.

I am well aware of the fact that the human eye adapts to different ambient light and quickly adjusts its color reception accordingly. I still assume that it would be possible to find a way to create a standardized background light and measure how the human eye, adapted to this standardized background light, would typically perceive the color of different objects in space.

I am well aware that many objects in space are too faint for the human eye to perceive color in them. All right. I believe that there may be brighter objects of the same color, or rather of the same hue, and that it would be possible for humans to understand the hue of the fainter object by looking at the brighter object of the same hue.

Take galaxies. I believe that I understand the colors, and certainly the hues, of galaxies. The first time I saw the Andromeda galaxy at the age of fifteen, I had only seen a black and white picture of it, and I had no idea of what it would look like to my eye. It looked like soft yellowish patch of light. The yellowish color was very obvious. I saw it not because I was expecting it, but because I saw it. Many years later I spent a long time looking carefully through a telescope at the colors of bright stars of all spectral classes. I looked at very many different stars, and I also looked at many of the brightest stars over and over again. In the end, I felt confident that I really knew and could remember their colors.

Because I feel that I know the colors of stars, I also feel that I know the colors of galaxies. As I said, the Andromeda galaxy looked yellowish when I first saw it. Since then, I have seen very similar yellowish hues in, typically, K-type stars. I believe I can say that the overall color of the bulge of the Andromeda galaxy is very comparable to a K-type star.

Bright and moderately unreddened starforming regions, rich in O-type stars, can definitely be expected to look the same color as an unreddened O-type star. I have never seen the Large Magellanic Cloud or the fantastic star cluster R136, but I don't doubt that R136 is more or less the same color as an O-type star.

As for blue reflection nebulas, I think of them as extremely faint but even bluer in color than the stars whose light they reflect. I have seen the brighter members of the Pleiades many times, and I have often seen their blue color. Therefore I don't doubt that the reflection nebulas are even bluer than the bright blue stars themselves.

I also understand that the bright reflection nebula lit up by Antares should be yellow, since Antares emits copious amounts of yellow, orange and red light, but extremely little blue light.

As for Ha emission, I have most certainly never seen the color of it - and no one else has, either. I simply trust the RGB images of emission nebulas. They are very consistently shown as typically pink, which is the color you would expect from a lot of circa 656 nm Ha light mixed with a smaller quantity of circa 486 nm Hβ light. The sheer consistency of the pink color of emission nebulas in a very large number of RGB pictures made by many different photographers is convincing to me. Yes, I can understand that the pink color of emission nebulas may have become an established ideal, so that photographers might strive to make their RGB images of emission nebulas look pink simply because they feel that they should look like that. I realize that that is a risk. But to me, the pink color makes such good sense in view of the wavelengths of Ha and Hβ light, that I simply accept it.

I find the OIII color frustrating and hard to picture. I have never seen it myself, and pictures, even RGB pictures, of planetary nebulas are not consistent. Some pictures show the OIII-bright parts of the planetaries as blue, some show them as aqua and some show them as green. To add to the confusion, a few planetaries look consistently blue in several pictures by different photographers. It is a complete mystery to me why a few planetaries should look decidedly bluer than others. Is their OIII light bluer than the other planetaries' OIII light?

And anyway, planetaries look so different in color pictures. Consider this planetary, and this, and this, and this, and this, and this, and this. Why do their colors look so very different? How can I understand it?

Geckzilla would have told me that there is nothing to understand. The pictures show what they show and that's enough. I get that. I realize that these pictures are extremely valuable to people trying to understand the inner workings of planetary nebulas. I certainly don't protest when people are happy and excited when they look at pictures of planetaries similar to those I have just proved links to.

It is just that I see a cacophony of weird colors when I look at them.

Ann
Color Commentator
User avatar
Ann
4725 Å
 
Posts: 5741
Joined: Sat May 29, 2010 5:33 am

Re: APOD: A Halo for NGC 6164 (2014 May 22)

Postby geckzilla » Sat May 24, 2014 7:25 pm

I didn't mean that there is nothing to understand, just that there is no need to translate anything based on what you would consider to be a universal language of color. I could try to use this analogy. The words are light, the instrument is the translator, and the universal language is mathematical, not the color itself.
Just call me "geck" because "zilla" is like a last name.
User avatar
geckzilla
Ocular Digitator
 
Posts: 5712
Joined: Wed Sep 12, 2007 12:42 pm
Location: Fresh Meadows, NY

Re: APOD: A Halo for NGC 6164 (2014 May 22)

Postby starsurfer » Sun May 25, 2014 1:03 pm

Chris Peterson wrote:
starsurfer wrote:I think that part of the ionization for the outer part is the energy generated by the gas colliding into the surrounding interstellar medium. I'm amazed that supernova remants can continue glowing for thousands of years!!

I'm not sure you're suggesting it, but to be clear, this isn't a supernova remnant.

That said, maybe you should be surprised that material of several solar masses can be heated to the point that it emits as much energy as an entire galaxy, and yet only glow for a few thousand years!

I didn't mean to imply I thought this object was a supernova remnant but I like to go in slightly related tangents as well as random. I know that the energy output of ionized gas is very high, which is why quite a few also exhibit x-ray emission. I just happen to find the universe amazing!!
starsurfer
Commander
 
Posts: 996
Joined: Thu Mar 15, 2012 7:25 pm

Re: APOD: A Halo for NGC 6164 (2014 May 22)

Postby starsurfer » Sun May 25, 2014 1:11 pm

Ann wrote:
geckzilla wrote:
Ann wrote:Well, this isn't a planetary nebula, and I have no problems forming a mental picture of the "true" colors here.

This object isn't especially from a planetary nebulas different as far as colors go. Many planetary nebulas are also imaged in H-alpha and OIII. The blue outer shell for NGC 6164 is nearly invisible without narrowband data. Congratulations, you just tricked yourself into overcoming your bias against narrowband.


NGC 6164 isn't hard to understand, colorwise. There is a bright blue O star in the middle, surrounded by two lobes of ordinary red Ha emission. There is an extremely faint outer halo that I admittedly can't quite imagine, since I'm generally unsure about the true color of OIII light. But then again, the outer halo is so faint that I'm quite okay about not being able to truly imagine it.

Planetary nebulas are so much more confusing. There is no way I can imagine the true colors of NGC 7072, for example.

Ann

I used to feel that way about narrowband a long time ago. However, just because an image contains narrowband data doesn't necessarily make it false colour, it depends on the processing. Although this image does include Ha and OIII, it has been processed in a way that approximates "true" colour. If it wasn't for the high contrast of narrowband, lots of things would be invisible. In fact in the past 10 years, more than 1000 new planetary nebulae and dozens of new supernova remnants have been discovered in Ha surveys. Even amateurs have discovered new things in their own personal deep narrowband images, the Soap Bubble Nebula being a good recent example.

The colour of OIII is generally blue but can also be green or turquoise. In many nebulae, there are areas where both Ha and OIII overlap and their colours are generally pink or purple. It also depends on the processing, most narrowband images are processed using the bicolour approach, which more clearly shows the separate Ha and OIII parts but the colour is less "truthful".

Adam Block has an excellent "true" colour image of NGC 7027 here: http://www.caelumobservatory.com/gallery/n7027.shtml

If you ever want to know if a narrowband image is true or false colour in the future, just PM me!

In OIII we trust! :D
starsurfer
Commander
 
Posts: 996
Joined: Thu Mar 15, 2012 7:25 pm

Next

Return to The Bridge: Discuss an Astronomy Picture of the Day

Who is online

Users browsing this forum: Google Feedfetcher, Yandex [Bot] and 2 guests