Starship Asterisk*

The Colorful Clouds of Rho Ophiuchi

Explanation: The many spectacular colors of the Rho Ophiuchi (oh'-fee-yu-kee) clouds highlight the many processes that occur there. The blue regions shine primarily by reflected light. Blue light from the star Rho Ophiuchi and nearby stars reflects more efficiently off this portion of the nebula than red light. The Earth's daytime sky appears blue for the same reason. The red and yellow regions shine primarily because of emission from the nebula's atomic and molecular gas. Light from nearby blue stars - more energetic than the bright star Antares - knocks electrons away from the gas, which then shines when the electrons recombine with the gas. The dark brown regions are caused by dust grains - born in young stellar atmospheres - which effectively block light emitted behind them. The Rho Ophiuchi star clouds, well in front of the globular cluster M4 visible above on lower left, are even more colorful than humans can see - the clouds emits light in every wavelength band from the radio to the gamma-ray.

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I must protest!

APOD Robot wrote:

The red and yellow regions shine primarily because of emission from the nebula's atomic and molecular gas.

That's not true! Yes, the red nebula we can see here - a small and rather faint crescent-shaped reddish-pink nebula to the lower right of Sigma Scorrpi, a binary star containing an O-type component - does indeed shine because of Ha emission. But the large yellowish nebula in the upper part of the picture does not shine from emission at all! Instead, this nebula is that rare kind of bird, a yellow reflection nebula. It is yellow because the illuminating star, red giant Antares, contains very little blue light in the first place that could be scattered by the nebula, and also because the yellowest parts of the nebula are almost certainly relatively "thick" and scatter much of the blue and green light that is there away from us.

Note, too, that the stars that are surrounded by blue reflection nebulae are all significantly bluer in color than the sun. So these nebulae are blue not just because reflection nebulae are always blue (they aren't), but because the nebulae that scatter the blue starlight our way are also illuminated by the kind of stars that give them a lot of blue light to scatter.

Nice picture!

Ann

Jack..."The Pumpkin King".....

Awesome shot....M4 is very striking contrast...

Hope everyone had a Happy Thanksgiving....on to Xmas!!!

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In the upper left....the stars seem to form a temple...like an Aztec Step Temple, with an Observatory on top....COOL!!!

:---[===] *

About 1-o'clock from M4, there appears to be another globular cluster just inside the dust cloud. Is that NGC6144?

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Obquote: "Poof!" -Ison, ex comet.

Psnarf wrote:About 1-o'clock from M4, there appears to be another globular cluster just inside the dust cloud. Is that NGC6144?

Yes.

Ann

Ann wrote:... this nebula is that rare kind of bird, a yellow reflection nebula.

Or, as might be heard out in the hills, “That thar odd yeller nebular.”

Ann wrote:I must protest!

APOD Robot wrote:

The red and yellow regions shine primarily because of emission from the nebula's atomic and molecular gas.

That's not true! Yes, the red nebula we can see here - a small and rather faint crescent-shaped reddish-pink nebula to the lower right of Sigma Scorrpi, a binary star containing an O-type component - does indeed shine because of Ha emission. But the large yellowish nebula in the upper part of the picture does not shine from emission at all! Instead, this nebula is that rare kind of bird, a yellow reflection nebula. It is yellow because the illuminating star, red giant Antares, contains very little blue light in the first place that could be scattered by the nebula, and also because the yellowest parts of the nebula are almost certainly relatively "thick" and scatter much of the blue and green light that is there away from us.

Note, too, that the stars that are surrounded by blue reflection nebulae are all significantly bluer in color than the sun. So these nebulae are blue not just because reflection nebulae are always blue (they aren't), but because the nebulae that scatter the blue starlight our way are also illuminated by the kind of stars that give them a lot of blue light to scatter.

Nice picture!

Ann

You're right Ann, I applaud your courage to point this out! There are lots of other yellow reflection nebulae, many in the vdB catalogue. One of my favourites is the Toby Jug Nebula. Also another nice one is the unnamed one associated with the protostar V2493 Cygni (which developed as the result of an explosive outburst), it can be seen in this image by Antonio Sanchez: http://afesan.es/Deepspace/slides/LRGB% ... us%29.html

What an amazing APOD. There are so many interesting areas to investigate. Like the cluster hidden in the cloud upper right from M4. A photograph like this truly demonstrates why many of us are so fascinated by our universe and the structures in it. You could spend the entire day only superficially delving into its wonders. Thanks Rafael and APOD for bringing it to us!!

This is a beautiful picture of a fascinating area of the sky. There is so much to see here in one binocular field of view! Ancient stars in a globular cluster (or two), lots of very young stars, a bright red supergiant star, binary bright blue subgiant main sequence stars, several multiple stars systems, two colors of reflection nebulae, an emission nebula, and dark nebulae. From a dark location you can see all of this in binoculars, and even from the city you can see all the stars.

Unfortunately you can't see any of this right now, because the Sun is transiting this part of the zodiac. One more reason to look forward to Summer!

Anthony Barreiro wrote:
This is a beautiful picture of a fascinating area of the sky. There is so much to see here in one binocular field of view! Ancient stars in a globular cluster (or two), lots of very young stars, a bright red supergiant star, binary bright blue subgiant main sequence stars, several multiple stars systems, two colors of reflection nebulae, an emission nebula, and dark nebulae. From a dark location you can see all of this in binoculars, and even from the city you can see all the stars. Unfortunately you can't see any of this right now, because the Sun is transiting this part of the zodiac. One more reason to look forward to Summer!

But we don't yet know if it will survive grazing the sun

neufer wrote:

[b][color=#0000FF]Colorful Clouds of Rho Ophiuchi as seen in a SOHO coronagraph. Credit: NASA/ESA, Astrobob [/color][/b]

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Anthony Barreiro wrote:
This is a beautiful picture of a fascinating area of the sky. There is so much to see here in one binocular field of view! Ancient stars in a globular cluster (or two), lots of very young stars, a bright red supergiant star, binary bright blue subgiant main sequence stars, several multiple stars systems, two colors of reflection nebulae, an emission nebula, and dark nebulae. From a dark location you can see all of this in binoculars, and even from the city you can see all the stars. Unfortunately you can't see any of this right now, because the Sun is transiting this part of the zodiac. One more reason to look forward to Summer!

But we don't yet know if it will survive grazing the sun

Fellow asternauts, please don't listen to anything Art says.

Anthony Barreiro wrote:
Fellow asternauts, please don't listen to anything Art says.

• At least I didn't state:

<<The red and yellow regions shine primarily because of emission from the nebula's atomic and molecular gas.>>

I could guess what red and yellow make but I know this shows my density -

Rho, Rho, Rho your light
Gently down the wave
Merrily, merrily, merrily, merrily
Life is brown dust grains

http://www.physics.sjsu.edu/tomley/Obje ... iuchi.html
Has a nice image of this region, together with details of the various nebulae.

BDanielMayfield wrote:

Ann wrote:... this nebula is that rare kind of bird, a yellow reflection nebula.

Or, as might be heard out in the hills, “That thar odd yeller nebular.”

Thar it is!!!

Ann

An amazing APOD. I have made a mental note to take a closer look at this part of the sky in mid 2014 (no matter the season). There is a diverse range of beautiful photographs on Rafael Defavari's website. Thank you.

Here is another picture of the Antares and Rho Ophiuchi cloud complex. What is interesting about this picture is that it shows us a second red emission nebula in this area, a large but faint one surrounding B0-type main sequence star Tau Scorpii. This red emission nebula partly overlaps or possibly impinges on the yellow reflection nebula surrounding Antares. Therefore low levels of red-emitting Ha ions might be mixed with some of the yellow nebulosity of Antares. It is even possible that a collision between these two clouds of nebulosity does indeed produce some Ha emission due to the force of the collision itself. But if so, we are talking about very low levels of Ha emission, which is invisible in today's APOD.

The red nebulosity around Tau Scorpii is particularly visible here.

I talked about a "crescent-shaped" red nebula near Sigma Scorpii. The red crescent is beautifully obvious in infrared images.

Ann

starsurfer wrote: There are lots of other yellow reflection nebulae, many in the vdB catalogue. One of my favourites is the Toby Jug Nebula. Also another nice one is the unnamed one associated with the protostar V2493 Cygni (which developed as the result of an explosive outburst), it can be seen in this image by Antonio Sanchez: http://afesan.es/Deepspace/slides/LRGB% ... us%29.html

Thanks for calling attention to the Toby Jug Nebula, Starsurfer! Of course, I feel a little bit like Kari in the Incredibles when I think that there is something weird going on in the Toby Jug Nebula, so that my gut feeling, whatever that is worth, thinks that there might just possibly be something more than just reflected light coming out of this system. But there is most certainly a yellow reflection nebula here!

And thanks for the picture of the yellow nebula around the protostar in Cygnus!

Ann

Oh, and... can't resist. Here's more of Kari the babysitter!

MargaritaMc wrote:http://www.physics.sjsu.edu/tomley/Obje ... iuchi.html
Has a nice image of this region, together with details of the various nebulae.

That is a very nice description. And San Jose State University is in my neck of the woods, just down the road a piece in Silicon Holler. I hear that Doctor Les Tomley is a stand-up feller.

Nitpicker wrote:An amazing APOD. I have made a mental note to take a closer look at this part of the sky in mid 2014 (no matter the season). There is a diverse range of beautiful photographs on Rafael Defavari's website. Thank you.

No slight intended to you denizens of the southern hemisphere. I rather envy your long winter nights to look at Scorpius and Sagittarius high overhead.

Anthony Barreiro wrote:

Nitpicker wrote:An amazing APOD. I have made a mental note to take a closer look at this part of the sky in mid 2014 (no matter the season). There is a diverse range of beautiful photographs on Rafael Defavari's website. Thank you.

No slight intended to you denizens of the southern hemisphere. I rather envy your long winter nights to look at Scorpius and Sagittarius high overhead.

Not even slightly offended by your unintended slight.

One day [when my family no longer loves me and I live lonely on top of a hill] I will get an equatorially mounted scope. The alt-az mount I currently own, doesn't track very well near zenith (where the centre of the galaxy just happens to pass daily for me). I also cannot fit my [wife's] camera to my scope when pointing near my zenith, unless I use a diagonal, which I dislike doing. For celestial objects that pass near my zenith, I tend to wait until they are lower in my western sky, which is much darker and less obstructed than my eastern sky. On the other hand, an alt-az mount is faster to setup and align, which probably makes me use the scope more, which is probably the most important factor [family is also important].

Nitpicker wrote:

Anthony Barreiro wrote:

Nitpicker wrote:An amazing APOD. I have made a mental note to take a closer look at this part of the sky in mid 2014 (no matter the season). There is a diverse range of beautiful photographs on Rafael Defavari's website. Thank you.

No slight intended to you denizens of the southern hemisphere. I rather envy your long winter nights to look at Scorpius and Sagittarius high overhead.

Not even slightly offended by your unintended slight.

One day [when my family no longer loves me and I live lonely on top of a hill] I will get an equatorially mounted scope. The alt-az mount I currently own, doesn't track very well near zenith (where the centre of the galaxy just happens to pass daily for me). I also cannot fit my [wife's] camera to my scope when pointing near my zenith, unless I use a diagonal, which I dislike doing. For celestial objects that pass near my zenith, I tend to wait until they are lower in my western sky, which is much darker and less obstructed than my eastern sky. On the other hand, an alt-az mount is faster to setup and align, which probably makes me use the scope more, which is probably the most important factor [family is also important].

I much prefer an equatorial to an altazimuth mount. The equatorial is much more elegant and graceful, moving as things move across the sky, rather than needing to approximate an arc from line segments. Once you've done it a few times, a non-go-to equatorial mount takes less than a minute for a good-enough polar alignment. And the equatorial mount just loves to look straight up at the zenith! The only down side is that you'll have a harder time observing Sigma Octantis.

I do still have my first altazimuth mount, I use it mostly for quick looks at the Moon or planets when they're not too far from the horizon.

Anthony Barreiro wrote:I much prefer an equatorial to an altazimuth mount. The equatorial is much more elegant and graceful, moving as things move across the sky, rather than needing to approximate an arc from line segments. Once you've done it a few times, a non-go-to equatorial mount takes less than a minute for a good-enough polar alignment. And the equatorial mount just loves to look straight up at the zenith! The only down side is that you'll have a harder time observing Sigma Octantis.

I do still have my first altazimuth mount, I use it mostly for quick looks at the Moon or planets when they're not too far from the horizon.

The things I like about my alt-az goto scope are:

1) It is programmable (I have a long term plan to develop various bits of software for any device using the published NexStar Communication Protocol, including better tracking accuracy ).

2) You can "shoot blind" with a camera at dim objects, because you have pretty accurate coordinates in RA,DE. This makes mosaics easier too.

3) I don't have to star-hop, and I can saves positions and re-find things quickly on subsequent nights.

4) It is easier to align with the sky accurately, no matter where I set the tripod (I need to fully unpack/pack the scope each session).

5) It typically allows for more comfortable viewing positions.

...

I would still like an equatorial mount as well, though, primarily for photography, but I'd want it to be a goto. I'm hooked on gotos.

Ann wrote:Here is another picture of the Antares and Rho Ophiuchi cloud complex. What is interesting about this picture is that it shows us a second red emission nebula in this area, a large but faint one surrounding B0-type main sequence star Tau Scorpii. This red emission nebula partly overlaps or possibly impinges on the yellow reflection nebula surrounding Antares. Therefore low levels of red-emitting Ha ions might be mixed with some of the yellow nebulosity of Antares. It is even possible that a collision between these two clouds of nebulosity does indeed produce some Ha emission due to the force of the collision itself. But if so, we are talking about very low levels of Ha emission, which is invisible in today's APOD.

The red nebulosity around Tau Scorpii is particularly visible here.

I talked about a "crescent-shaped" red nebula near Sigma Scorpii. The red crescent is beautifully obvious in infrared images.

Ann

The red emission nebula around Tau Scorpii is catalogued as RCW 129. Also Ann, a surprise hug for you!!