APOD: Aurigae Nebulae (2012 Feb 24)

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APOD: Aurigae Nebulae (2012 Feb 24)

Post by APOD Robot » Fri Feb 24, 2012 5:07 am

Image Aurigae Nebulae

Explanation: Rich in star clusters and nebulae, the ancient constellation of Auriga, the Charioteer, rides high in northern winter night skies. Composed from narrow and broadband filter data and spanning nearly 8 Full Moons (4 degrees) on the sky, this deep telescopic view recorded in January shows off some of Auriga's celestial bounty. The field includes emission region IC 405 (top left) about 1,500 light-years distant. Also known as the Flaming Star Nebula, its red, convoluted clouds of glowing hydrogen gas are energized by hot O-type star AE Aurigae. IC 410 (top right) is significantly more distant, some 12,000 light-years away. The star forming region is famous for its embedded young star cluster, NGC 1893, and tadpole-shaped clouds of dust and gas. IC 417 and NGC 1931 at the lower right, the Spider and the Fly, are also young star clusters embedded in natal clouds that lie far beyond IC 405. Star cluster NGC 1907 is near the bottom edge of the frame, just right of center. The crowded field of view looks along the plane of our Milky Way galaxy, near the direction of the galactic anticenter.

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Re: APOD: Aurigae Nebulae (2012 Feb 24)

Post by Aristaeus » Fri Feb 24, 2012 6:03 am

Would it be accurate to say that IC 410 is more than eight times larger than IC 405 - or is my math screwed up somehow?

romanian nebula

Re: APOD: Aurigae Nebulae (2012 Feb 24)

Post by romanian nebula » Fri Feb 24, 2012 6:51 am

this article links to another apod titled spider and fly - however if you look closely, either that apod or this one from today is flipped upside down! observe the two bright stars between spider and fly - so which image was flipped and which is the right one ?!

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Re: APOD: Aurigae Nebulae (2012 Feb 24)

Post by nstahl » Fri Feb 24, 2012 10:10 am

Aristaeus wrote:Would it be accurate to say that IC 410 is more than eight times larger than IC 405 - or is my math screwed up somehow?
Your math is fine. If we say they look the same size then one being eight times as far away, it's eight times as big - in linear measurement. In volume it would be eight cubed or 512 times as big.

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Re: APOD: Aurigae Nebulae (2012 Feb 24)

Post by nstahl » Fri Feb 24, 2012 10:20 am

The "ancient constellation of Auriga" link in the Explanation refers back to this same APOD.

May we assume it's the naming of that constellation that's ancient, not the stars in it. "Ancient" being a relative term.

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Re: APOD: Aurigae Nebulae (2012 Feb 24)

Post by owlice » Fri Feb 24, 2012 11:12 am

Thanks, nstahl; I've sent a note to the editor.
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Re: APOD: Aurigae Nebulae (2012 Feb 24)

Post by Tszabeau » Fri Feb 24, 2012 1:26 pm

This nebula should be named The Juggler. IMHO

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Re: APOD: Aurigae Nebulae (2012 Feb 24)

Post by Ann » Fri Feb 24, 2012 1:32 pm

Auriga is a fascinating and beautiful constellation with a lot of clusters and nebulae. Today's APOD brings out several of these nebulae and a few of the clusters beautifully.

However, for me as a color freak, it is obvious that the blue color of IC 405 and the blue color of IC 410 means different things. In IC 405, the Flaming Star nebula, the blue color is ordinary reflection nebulosity, not really different from the blue reflection nebulosity of the Pleiades. But this kind of reflection nebulosity is rarely seen close to O-type stars. Why is that?

The reason is that the dust that does the reflection is dispersed or destroyed by the hot O-type stars. Stars, including O-type stars, are born out of clouds of gas and dust. The O-type stars are incredibly energetic right from the start. When they are first born, they are often still cocooned in thick gas clouds that are made to glow red, as is the case of the O-type stars of M17. Here the stars haven't broken through their stellar cocoon, and we can only see the red nebulosity. Or else we may actually see the stars, but their intense ultraviolet light makes both the surrounding hydrogen and oxygen strongly ionized, so that they emit red and green light, as is the case with the Trapezium Cluster. There is little blue reflection nebulosity to be seen here.

So why is O-type star AE Aurigae "swimming in blue-reflecting dust"" in the middle of the red Flaming Star nebula? It is because AE Aurigae is just passing through this cloud of gas and dust. AE Aurigae was not born here, so it never had to break out of a thick dusty cocoon in the middle of this red cloud. And precisely because AE Aurigae is just passing through, it hasn't had time to blow away the dust in its vicinity or "cook" the dust grains to a smaller size. It hasn't had time to blow a rarefied cavity where oxygen can be ionized and glow aqua-green. So just because AE Aurigae is such a temporary visitor, it is dressed in blue swirls of reflecting dust.

What about the blue light that can be seen in IC 410, the nebula to the right of the Flaming Star nebula in this image? Is this nebula also full of dust that is glowing blue from reflection? No, I find that quite unlikely. IC 410 is a very different nebula from IC 405. The hot stars were born here and have blown a cavity in the center of their birth cloud. There shouldn't be be much dust here to reflect the light of the hot blue stars inside. Of course it is still possible to "weight" the color balance in this kind of image to underscore the fact that the red IC 410 nebula is made to glow red by the blue stars inside.

I'm fascinated by "The Spider and The Fly" nebulae in this image. The Fly, in particular, looks very compact, bright and relatively small. I'm actually reminded of the Orion Nebula and what it would look like if it was very far away.

The cluster NGC 1907 at bottom center right is interesting. According to Wikipedia it is probably at least 500 million years old. You can actually tell from its appearance that it is moderately old, since most of the stars in it appear to be pretty much the same brightness, and the cluster doesn't stand out in a really remarkable way from its surroundings. So there are no extremely bright young stars here.

Finally, look at the group of stars located between the two conspicuous red nebulae here, IC 405 and IC 410.The group of stars are an asterism, which means that they don't belong together, but are a line-of-sight coincidence. The asterism is called "The Leaping Minnow". I like the name! And some of the stars are interesting. The bottom blue star in this image is an A-type giant, probably more than 3,000 times as bright as the Sun. The middle blue star is a "magnetic silicon star", classified as spectral class A0p (peculiar). It is the hottest and the bluest of all stars classified as A-type stars, with a temperature of about 17,000 Kelvin, typical of a B4 star.

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Re: APOD: Aurigae Nebulae (2012 Feb 24)

Post by orin stepanek » Fri Feb 24, 2012 1:41 pm

I learned a new term today; anticenter! :wink: :thumb_up: :b:
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Re: APOD: Aurigae Nebulae (2012 Feb 24)

Post by Ann » Fri Feb 24, 2012 3:14 pm

I just got a very kind PM from Steve Cannistra, the photographer behind today's APOD. In his PM, Steve Cannistra wrote, among other things:
In fact, you will notice that the shade of blue is different between these two nebulae- IC405 is very blue, consistent with a pure reflection component, whereas IC410 is blue-green, consistent with a (likely) emission component from OIII.

Capturing the bluish central region of IC410 using a broadband blue filter is not always easy- it requires very deep, high signal to noise blue signal, which I was fortunate to acquire. You may notice that some other broadband renditions of IC410 do not always show the central blue component, and instead appear rather monochromatic in the red region. This may be due to the fact that the blue signal is relatively weak, and the Ha signal (red) is allowed to dominate such images. In so doing the nuanced color distinction between central and peripheral regions of IC410 can be lost.
Thank you for your comment, Steve! :D And thank you again for your fine APOD.

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Re: APOD: Aurigae Nebulae (2012 Feb 24)

Post by neufer » Fri Feb 24, 2012 4:06 pm

http://en.wikipedia.org/wiki/The_Chariot_%28Tarot_card%29 wrote:
Image
<<The Chariot is Key Seven of the Major Tarot Arcana, it represents the possibility of traveling through the mysteries of the universe. A powerful, princely figure sits in a swift chariot, pulled usually by two sphinxes. The charioteer is the Son of the Queen of Heaven. The canopy of his chariot is her starry gown; he wears the waxing and waning moon on his shoulders; the circle of the Zodiac is his belt. He channels energy from the world above (signified by the eight pointed star on his brow, eight here representing Venus) to the world below (signified by the square on his chest, the four corners of the Earth). The star can also represent the infinite, the square the earthly spheres of time and space. Waite describes the charioteer as conquest on all planes — in the mind, in science, in progress, and thus able to reply to the riddles of the sphinx. But he may warn that we are in danger of being pulled to pieces by forces we do not control and do not understand.

The Chariot represents a battle that can be won if you have the willpower for it. Qualities needed to win the battle include self-reliance, righteousness, conviction and plain hard work. The steeds represent powerful forces, internal or external, that can be controlled to achieve the goal. They pull in different directions, but must be (and can be!) made to go together in one direction. Control is required over opposing emotions, wants, needs, people, or circumstances; to bring them together and give them a single direction, your direction. Confidence is also needed and, most especially, motivation. If inverted, the meaning remains the same, but you are in danger of losing the battle due to a lack of control.

Structurally, the Chariot follows The Lovers. After the impulse that pulls us out of the Garden, we get on our chariot and depart. At that point, we are the Hero of our own story; maybe the Hero of everyone’s story. That Hero might represent Helios, the Greek god who drives the Sun’s chariot across the sky, bringing light to the earth. The danger of this card is well illustrated by the myth of Phaëton. Among other things, this story illustrates the danger of reaching too high, unprepared.

Ra from Egyptian mythology piloted the boat of the sun across the sky and back to the gates of dawn down the Nile every night. One night, Apophis, Chaos and Old Night swallowed the river to keep the sun from rising. Fortunately, Ra’s usual enemy, Set, took it upon himself to save the day by slicing Apophis open, allowing Ra to escape. This story bespeaks the reversals of the night, where our deadly enemies may be our best friends. Another famous chariot driver was the god Krishna who in the Bhagavad Gita drove Arjuna’s chariot and gave him illumination.>>
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Re: APOD: Aurigae Nebulae (2012 Feb 24)

Post by Brambory » Fri Feb 24, 2012 6:54 pm

Has this many named nebula ever been called the Naked Lady Nebula? Just wondering...

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Re: APOD: Aurigae Nebulae (2012 Feb 24)

Post by Case » Fri Feb 24, 2012 10:09 pm

nstahl wrote:The "ancient constellation of Auriga" ...
May we assume it's the naming of that constellation that's ancient, not the stars in it. "Ancient" being a relative term.
One of the definitions of 'ancient' is
"of or relating to the historical period beginning with the earliest known civilizations and extending to the fall of the western Roman Empire in 476 A.D."
which includes 2nd century A.D. Claudius Ptolemy’s world. He is known for a list of 48 constellations, which includes Auriga.
That does indeed make Auriga an ancient constellation.

grixx

Re: APOD: Aurigae Nebulae (2012 Feb 24)

Post by grixx » Fri Feb 24, 2012 10:10 pm

my first impression of this Nebulae is to call it the Marilyn Monroe Nebulae (for a couple of reasons).
Grizz

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Re: APOD: Aurigae Nebulae (2012 Feb 24)

Post by Wolf Kotenberg » Fri Feb 24, 2012 11:14 pm

Got it. A scientist sees a red emission nebulae. A poet ( specially those ancient types ) see a spyder.

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Re: APOD: Aurigae Nebulae (2012 Feb 24)

Post by DavidLeodis » Sat Feb 25, 2012 11:07 am

orin stepanek wrote:I learned a new term today; anticenter! :wink: :thumb_up: :b:
So did I Orin. :)

In the information brought up through the galactic anticenter link it states:
Auriga has the distinction of being located in the direction of the Galactic Anticenter. What is an anticenter? It is the point in the night sky that is opposite the Galactic Center, of course :-) The center of the Milky Way Galaxy is located in the direction of the constellation Sagittarius, a dominant summertime constellation. So not surprising, in the winter time when we are looking the 'other direction' in the sky, we find ourselves staring out into space directly out of our Milky Way Galaxy.
Last edited by bystander on Sat Feb 25, 2012 7:19 pm, edited 2 times in total.
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Re: APOD: Aurigae Nebulae (2012 Feb 24)

Post by Chris Peterson » Sat Feb 25, 2012 2:55 pm

DavidLeodis wrote:The center of the Milky Way Galaxy is located in the direction of the constellation Sagittarius, a dominant summertime constellation. So not surprising, in the winter time when we are looking the 'other direction' in the sky, we find ourselves staring out into space directly out of our Milky Way Galaxy".
But our galaxy is a disc of finite dimension, so any direction we look we are actually staring out of the Milky Way. The worst directions for looking out of the galaxy are those that lie in the galactic plane- which includes Auriga and the anti-center. Like Sagittarius, Auriga lies at a galactic latitude of 0°. To look most effectively outside the galaxy we should look towards the galactic poles- latitude 90° and -90°: the constellations of Coma Berenices and Sculptor. When we look in those directions, most of what we see is external to the Milky Way.
Chris

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Re: APOD: Aurigae Nebulae (2012 Feb 24)

Post by DavidLeodis » Sat Feb 25, 2012 6:57 pm

Chris Peterson wrote:
DavidLeodis wrote:The center of the Milky Way Galaxy is located in the direction of the constellation Sagittarius, a dominant summertime constellation. So not surprising, in the winter time when we are looking the 'other direction' in the sky, we find ourselves staring out into space directly out of our Milky Way Galaxy".
But our galaxy is a disc of finite dimension, so any direction we look we are actually staring out of the Milky Way. The worst directions for looking out of the galaxy are those that lie in the galactic plane- which includes Auriga and the anti-center. Like Sagittarius, Auriga lies at a galactic latitude of 0°. To look most effectively outside the galaxy we should look towards the galactic poles- latitude 90° and -90°: the constellations of Coma Berenices and Sculptor. When we look in those directions, most of what we see is external to the Milky Way.
Just to make it clear I did not personally write that quote as it is part of the information that was brought up through the link that I mentioned in my earlier post. :)

Auriga and Capella: the Galactic Anticenter
Last edited by bystander on Sat Feb 25, 2012 7:13 pm, edited 1 time in total.
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Re: APOD: Aurigae Nebulae (2012 Feb 24)

Post by Urban Astronomer » Fri Mar 02, 2012 12:35 am

hi David - thanks for posting the quote about the Galactic Anticenter from my blog. I focus my blog on the non-scientific, casual city observer, hence my simplifications when talking about visualization of our galaxy.

hi Chris - you are correct in stating that the worst way to look out of the galaxy is to look anywhere in the galactic plane. The reason for my writing about the Galactic Anticenter is to provide a framework for thinking about our place in the galaxy. I give a lot of night sky tours at the Cal Academy in San Francisco and one the best ways I can give perspective is to help visitors see (for example) the ecliptic by pointing out a few guideposts along the ecliptic, or the Milky Way by pointing out a few guideposts such as the Galactic Center and Galactic Anticenter, our our direction of travel around the Milky Way by pointing out Vega (leading the Sun) and Sirus (trailing the Sun). I am just trying to give guidelines - not scientifically precise measures.

By the way, you mention that when we look toward the galactic poles (Coma Berenices and Sculptor) most of what we see is external to the Milky Way. I can believe that is true in an absolute sense. But for city dwellers or suburban observers, is that true? When we look with the unaided eye toward Coma Berenices, are we really seeing primarily outside of the Milky Way? My working assumption is that with the exception of Andromeda and maybe one or another galaxy, everything we see in the night sky from somewhat light-polluted locations is only Milky Way.

-- Paul

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Re: APOD: Aurigae Nebulae (2012 Feb 24)

Post by Chris Peterson » Fri Mar 02, 2012 12:42 am

Urban Astronomer wrote:By the way, you mention that when we look toward the galactic poles (Coma Berenices and Sculptor) most of what we see is external to the Milky Way. I can believe that is true in an absolute sense. But for city dwellers or suburban observers, is that true? When we look with the unaided eye toward Coma Berenices, are we really seeing primarily outside of the Milky Way? My working assumption is that with the exception of Andromeda and maybe one or another galaxy, everything we see in the night sky from somewhat light-polluted locations is only Milky Way.
Yeah, when we look with our eyes, it doesn't matter what direction we choose (or how dark the skies are); essentially everything we see is inside our galaxy (with the few very rare exceptions like M31). I was referring the narrow field view, as you get with a telescope, or what Hubble shows. When looking away from the galactic plane, you are pretty quickly looking between local stars, at what lies beyond the Milky Way. That's a lot harder to do looking towards the anti-center, and really difficult looking towards the center.
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Re: APOD: Aurigae Nebulae (2012 Feb 24)

Post by Urban Astronomer » Fri Mar 02, 2012 2:18 am

Chris Peterson wrote:Yeah, when we look with our eyes, it doesn't matter what direction we choose (or how dark the skies are); essentially everything we see is inside our galaxy (with the few very rare exceptions like M31). I was referring the narrow field view, as you get with a telescope, or what Hubble shows. When looking away from the galactic plane, you are pretty quickly looking between local stars, at what lies beyond the Milky Way. That's a lot harder to do looking towards the anti-center, and really difficult looking towards the center.
That is very clearly stated, Chris. That's excellent information for me to share with viewers next time I am giving night sky tours. It makes perfect sense, when you compare and contrast telescopic narrow fields (especially Hubble) versus naked eye. Of course, the one other item to consider is that looking in any direction, toward or away from the pole or center of our galaxy, there are 10x to 100x more stars that we don't see at all, the red dwarf stars. But that's another discussion entirely!

-- Paul

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