Starship Asterisk*

AE Aurigae and the Flaming Star Nebula

Explanation: AE Aurigae is the bright star below and left of center in this evocative portrait of IC 405, also known as the Flaming Star Nebula. Embedded in the cosmic cloud, the hot, variable O-type star energizes the glow of hydrogen along convoluted filaments of atomic gas, its blue starlight scattered by interstellar dust. But AE Aurigae wasn't formed in the nebula it illuminates. Retracing the star's motion through space, astronomers conclude that AE Aurigae was probably born in the Orion Nebula. Close gravitational encounters with other stars ejected it from the region, along with another O star, Mu Columbae, over two million years ago. The runaway stars have drifted in opposite directions ever since, separating at about 200 kilometers per second. This sharp, detailed image of IC 405 spans over 5 light-years at the nebula's estimated distance of 1,500 light-years in the northern constellation Auriga, the Charioteer.

<< Previous APOD

Discuss Any APOD

Next APOD >>

[/b]

APOD Robot wrote:
AE Aurigae is the bright star below and left of center in this evocative portrait of IC 405, also known as the Flaming Star Nebula. Embedded in the cosmic cloud, the hot, variable O-type star energizes the glow of hydrogen along convoluted filaments of atomic gas, its blue starlight scattered by interstellar dust. But AE Aurigae wasn't formed in the nebula it illuminates. Retracing the star's motion through space, astronomers conclude that AE Aurigae was probably born in the Orion Nebula. Close gravitational encounters with other stars ejected it from the region, along with another O star, Mu Columbae, over two million years ago. The runaway stars have drifted in opposite directions ever since, separating at about 200 kilometers per second. This sharp, detailed image of IC 405 spans over 5 light-years at the nebula's estimated distance of 1,500 light-years in the northern constellation Auriga, the Charioteer.

http://en.wikipedia.org/wiki/Mu_Columbae wrote:
<<Mu Columbae (μ Col, μ Columbae) is a star in the constellation of Columba. It is one of the few O-class stars that is visible to the unaided eye. The star is known to lie approximately 1,300 light years from our solar system. This is a relatively fast rotating star that completes a full revolution approximately every 1.5 days. Based on measurements of proper motion and radial velocity, astronomers know that this star and AE Aurigae are moving away from each other at a relative velocity of over 200 km/s. Their common point of origin intersects with Iota Orionis in the Trapezium cluster, some two and half million years in the past. The most likely scenario that could have created these runaway stars is a collision between two binary star systems, with the stars being ejected along different trajectories radial to the point of intersection.

In Chinese astronomy, Mu Columbae is called 屎, Pinyin: Shǐ, meaning Excrement, because this star is marking itself and stand alone in Excrement asterism. As part of the (extended Orion's Belt) Three Stars mansion the Toilet asterism contains the star, Alpha Leporis while the Excrement asterism is the star, Mu Columbae.">>

with all the red Flameing Star is a good name for this nebula.

Is this a particularly fast star? could it have planets around it, if so would an observer on such a world be aware of the speed through galaxy, great image ;0)

new view wrote:
Is this a particularly fast star?

At 100 km/s vis-a-vis it's neighbors it is a relatively fast star.

new view wrote:
could it have planets around it, if so would an observer on such a world be aware of the speed through galaxy.

AE Aurigaeans would be aware of their speed through galaxy by averaging the velocity of all the stars around it.

A very beautiful image indeed! Well done, Rolf!

For we metrically-challenged individuals, 100 km/second is about 220,000 miles per hour.

For the relativistically challenged, that's about 1/3000th the speed of light.

-Noel

Is it just me or does the vertical part of the red nebula on the right look like a neck topped with the head of a red dragon partly turned toward us? The area of the blue light from the star AE Aurigae would be the dragon's mouth while three dark areas not quite horizontal in the nebula farther back would be the eyes.

Danell wrote:
Is it just me or does the vertical part of the red nebula on the right look like a neck topped with the head of a red dragon partly turned toward us? The area of the blue light from the star AE Aurigae would be the dragon's mouth while three dark areas not quite horizontal in the nebula farther back would be the eyes.

It's just you.

Danell wrote: Is it just me or does the vertical part of the red nebula on the right look like a neck topped with the head of a red dragon partly turned toward us? The area of the blue light from the star AE Aurigae would be the dragon's mouth while three dark areas not quite horizontal in the nebula farther back would be the eyes.

I see the Dragon and I think it's awesome!

Thanks for this exquisite, aesthetically evocative, intellectually fascinating image, and thanks for supporting this forum!

How close to natural color is this image? I see from the source page http://www.stern-fan.de/Seiten/galerie_ ... gstar.html:

The colors are mapped to real colors:

light red = H-alpha
blue = blue
dark red= SII

colored stars overlay

In other words, if I were at the distance from this object where this would be the view with the naked eye, how closely would the colors match this image?

Thanks again.

Mr. Completely wrote:In other words, if I were at the distance from this object where this would be the view with the naked eye, how closely would the colors match this image?

No matter how close you were, the object would never be seen as anything but faint gray. It is too dim to stimulate color vision. However, assuming your eyes were sensitive enough to see the color, what you would see would be quite different in appearance than the image portrays.

Thanks! So, is this true of all the beautiful nebula photos we see? Or are some types of these objects luminous in visible light spectra? The Pleiades come to mind - not a nebula per se I suppose, but another lovely and frequently photographed object - isn't it the case that some 'nebulosity' is visible under good conditions from earth?

thanks again for your time

rebtest2 wrote:Thanks! So, is this true of all the beautiful nebula photos we see? Or are some types of these objects luminous in visible light spectra? The Pleiades come to mind - not a nebula per se I suppose, but another lovely and frequently photographed object - isn't it the case that some 'nebulosity' is visible under good conditions from earth?

Many nebulas are bright enough that the human eye can see them- that is evident in all the objects amateur astronomers view through their telescopes. Telescopes don't make objects brighter, only bigger. But there are really no nebulas that are bright enough to stimulate human color vision significantly, so they all appear substantially gray. (There are a very small number of bright nebulas, such as the Great Nebula in Orion, which are right on the hairy edge of being bright enough to show color, and a few people with good eyes and lots of observing practice are just able to pick up a hint of green. A few planetary nebulas are also bright enough to show a bit of color in the green range.)

Mr. Completely wrote:Thanks for this exquisite, aesthetically evocative, intellectually fascinating image, and thanks for supporting this forum!

How close to natural color is this image? I see from the source page http://www.stern-fan.de/Seiten/galerie_ ... gstar.html:

The colors are mapped to real colors:

light red = H-alpha
blue = blue
dark red= SII

colored stars overlay

In other words, if I were at the distance from this object where this would be the view with the naked eye, how closely would the colors match this image?

Thanks again.

Chris is quite right that you could never see the Flaming Star nebula as red, because our eyes are insensitive to red color and the nebula itself is very faint. And like Chris says, getting closer to a nebula doesn't make it brighter, only bigger. Chris is also right that if our eyes were much, much more sensitive - in which case ordinary daylight would probably blind us - so that we could actually detect color in emission nebulae like the Flaming Star nebula, then they probably still wouldn't look the way they do in photographs. The reason is that the red color of hydrogen and sulphur emission is very deep into the red part of the spectrum, and the red objects that we see around us in daily life are rarely this shade of red. In some ways, you could describe the bright red color of emission nebulosity in photos as "mapped color", not quite the same as it would appear to our eyes, if they were sensitive enough. Don't forget, however, that the deep red Ha light is mixed with some aqua-colored hydrogen beta light, and that mixture of colors might well be visible to super-sensitive eyes as reddish-pink.

As for the Pleiades, the nebulosity around them is much too faint to stimulate color response in human eyes. If our eyes were sensitive enough, though, it wouldn't be difficult to see the blue color of the nebula. In principle, it should not be a lot more difficult to detect the blue color of the nebulosity around the Pleiades for a person with ultra-sensitive color vision than it is for us with ordinary human eyes to detect the blue color of the Earth's sky, because the Earth's sky can be regarded as a sort of reflection nebula, too. The main difference is that the Earth's blue sky is concentrated in a thin layer and very bright, whereas the Pleiades nebulosity is very spread out, very diffuse, and therefore very faint.

Ann

Thanks to both of you for your detailed and on-point answers.

If I might continue following up:

Telescopes don't make objects brighter, only bigger. But there are really no nebulas that are bright enough to stimulate human color vision significantly, so they all appear substantially gray. (There are a very small number of bright nebulas, such as the Great Nebula in Orion, which are right on the hairy edge of being bright enough to show color

What I'm trying to grasp is what these objects would look like if seen with the human eye: can a level of detail approximately equal to these photos, now disregarding color and accepting that the objects would in general appear in grayscale, be perceived? Whether through a telescope or by physically being closer is I suppose irrelevant.

The answer in the case of this particular object appears to be that it wouldn't look like much - "very faint" as Ann says. But, take the Great Nebula as Chris mentions above - are there locations within it where these beautifully detailed structures are visible to human sight, even if they would appear monochromatic? Or other such examples, perhaps - I assume size isn't the issue, but that it has more to do with the density of material and the amount of energy hitting it?

If so, do you know of photos that demonstrate this view? I have nonspecific memories of seeing the Horsehead in visible light, a much less detailed structure than the modern composite images, but I can't locate such an image on the public internets. Perhaps only silhouetting dark nebulas like the horsehead would show much such structure to the naked eye, telescopically enhanced or otherwise? Also perhaps I am now totally guessing?

If I have exceeded your already very generous explaining-things-to-laypeople quota for the day or week, by all means move along with your lives with nothing but my continued gratitude. I have to answer laypeople's questions about advanced web technology pretty often, so I'm aware it can sometimes be like trying to explain algebra to a cat.

MrCompletely wrote: If so, do you know of photos that demonstrate this view?

flaming star nebula region by erwin kats, on Flickr

Well, in order to see much of a nebula at all, the nebula needs to be fairly bright. The brighter it is, the more you can see of it. The Orion Nebula is obviously the brightest nebula in the sky as seen from the Earth's location, and the Orion Nebula definitely shows quite a bit of structure in a telescope. Don't expect nearly as much structure as you can see in photographs, though.

Here is an image which, in my opinion, gives you a pretty good idea of what you can hope to see in the Orion Nebula. The image shows the brightest part of it, the Trapezium:

http://www.starfieldobservatory.com/ima ... -%20xa.jpg

As for the Horsehead Nebula, it is notoriously difficult to see. The reason is that the Horsehead is a dark shape seen against a background which is "illuminated" by Ha light, which in itself is basically impossible for humans to see, when it is faint and spread out as it is in a nebula. Indeed, we are basically unable to spot Ha light even as colorless gray light source. Both our color-sensitive cones and our color-blind rods are extremely bad at detecting light which is very far into the red part of the spectrum.

But the red Ha light is always mixed with some hydrogen beta light, which we can see, since it is aqua-colored and therefore triggers response both in our green-sensitive and our blue-sensitive cones. It triggers an even stronger response in our color-blind rods, which is why we can see this light as gray. But there is always a lot less hydrogen beta light than there is Ha light in a nebula, so if the nebula is faint there is very little aqua-colored light there for us to see as gray. The emission nebula behind the Horsehead is not particularly bright, and certainly nowhere near as bright as the Orion Nebula. The best way to see the Horsehad, however, is to use a hydrogen beta filter which will block out all light except the aqua-colored hydrogen beta. The filter will make it easier for you to spot the hydrogen beta light from the emission nebula behind the Horsehead, and if you can see the hydrogen beta light (which will most certainly just look gray because it is so faint), you may spot the dark shape in front of the "gray wall of hydrogen beta light".

Ann

If you want to know which nebulae are the easiest to spot, why not check out the Messier Catalogue? Messier, who lived in the 18th century, lived under dark skies. The nebulae that he found are generally the brightest, although we should of course remember that he couldn't see much of the southern sky - he couldn't see the Eat Carina Nebula, for example.

Nevertheless, Wikipedia has a rather good description of the Messier objects at http://en.wikipedia.org/wiki/List_of_Messier_objects. Here you can see how few of the Messier objects are actually nebulae. Only twelve of 110 objects in his (extended) catalog are nebulae.

Ann

MrCompletely wrote:What I'm trying to grasp is what these objects would look like if seen with the human eye: can a level of detail approximately equal to these photos, now disregarding color and accepting that the objects would in general appear in grayscale, be perceived? Whether through a telescope or by physically being closer is I suppose irrelevant.

You will see much less structure with the eye than you will in images. That's because the light levels are very low, and as a result your acuity is pretty low, and your contrast perception is low. Take an image and look at it in very dim light and you'll see how much detail is lost to the eye.

Images capture data over a wide dynamic range, and have their contrast stretched so that the dimmest parts appear black and the brightest parts are white. That will never be the case for a nebula seen with the eye.

Thanks again to all of you for your thoughtful replies. I appreciate the images and pointers to further information.

Now one more thing...

kidding!