APOD: NGC 7023: The Iris Nebula (2012 Sep 29)

[APOD Robot]

NGC 7023: The Iris Nebula

Explanation: Like delicate cosmic petals, these clouds of interstellar dust and gas have blossomed 1,300 light-years away in the fertile star fields of the constellation Cepheus. Sometimes called the Iris Nebula and dutifully cataloged as NGC 7023 this is not the only nebula in the sky to evoke the imagery of flowers. Still, this remarkable image shows off the Iris Nebula's range of colors and symmetries in impressive detail. Within the Iris, dusty nebular material surrounds a hot, young star. The dominant color of the brighter reflection nebula is blue, characteristic of dust grains reflecting starlight. Central filaments of the dusty clouds glow with a faint reddish photoluminesence as some dust grains effectively convert the star's invisible ultraviolet radiation to visible red light. Infrared observations indicate that this nebula may contain complex carbon molecules known as PAHs. The bright blue portion of the Iris Nebula is about six light-years across.

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[Ann]

There's been a blue bonanza at APOD lately!

And Tony Hallas is back! He is another "classic" name, a great astrophotographer who has been around for a long time. Welcome back to APOD, Tony!

As for the lovely picture, I believe that Tony has slightly "enhanced" the color of it. I have certainly no problem with that, because it makes it so much easier to extract great color information from it!

As the APOD caption points out, there are pink structures inside this "floral sea of blue", suggesting emission nebulosity. I find it interesting to see the brown dust surrounding the Iris Nebula. Near the borders between the blue Iris and the unilluminated brown dust are what could be two small newborn stars in the process of having baby antics. At two o'clock is a small whitish star which might even be surrounded by a dark protoplanetary disk. On both sides of that dark disk are what looks like whitish outflows. At eight o'clock or eight thirty is a small red star, possibly with a dark protoplanetary disk, and two reddish outflows. The difference in color between these possible baby stars could be a difference in dust reddeneing. In any case, the Iris Nebula could well be a place where low-mass star formation is still going on.

It's a great picture and so beautiful!

Ann

[mrchrisgb]

I think I see a 'shadow line' running appr 45deg cw which reminds me of an interpretation of our Milky way. ie as if we are looking at a spiral, edge-on.
What do I know.

Chris.
mr.chris.gb@gmail.com

[orin stepanek]

It's a great picture and so beautiful!

Ann

It is indeed beautiful! Somehow I knew you'd like it Ann!

[Phil P.]

LOL, I read the title too fast and thought it said "Irish" nebula. Must be in O'Ryan.

[Boomer12k]

Ooooooo.....Great impressive pic....

My father, 89, grows Irises...Dalias, roses, miniature roses, a garden of veggies, strawberries, rasberries..apples, peaches, prunes...YUMMY.... We use Gravenstein Apples for our APPLE CRISP...we had several recently....YUMMY!!!! Made with Gluten free Bisquick, it is very light, not heavy, and we use no Oatmeal, or wheat flour, so it is not heavy...CRUMBLES IN YOUR MOUTH!!!!!!!!!!!! OOOOOOOHHHHHH!!!!!!

If we were in close proximity the sky should be awesome....but I wonder if the human eye can perceive all that blueness....

ALSO...QUESTION....how does the dust...take INVISIBLE ULTRAVIOLET LIGHT and MAKE VISIBLE RED LIGHT????? Somehow it slows down the wavelength?????

:---[===] *

[Ann]

Boomer12K wrote:
ALSO...QUESTION....how does the dust...take INVISIBLE ULTRAVIOLET LIGHT and MAKE VISIBLE RED LIGHT????? Somehow it slows down the wavelength?????

The dust isn't doing anything. Hydrogen gas is emitting the red light when it becomes ionized. An ultraviolet photon strikes a hydrogen atom and kicks the electron into a higher orbit around the proton. In this higher orbit, the electron contains more energy than it does in its "ground state". But after a while, the electron radiates away the extra energy it received, and in so doing, falls down to its ground state again.

The extra energy that the electron sheds is radiated away as a photon corresponding to a wavelength of 656 nm, or red Ha light.

Ann

[Beyond]

The extra energy that the electron sheds is radiated away as a photon corresponding to a wavelength of 656 nm, or red Ha light.

Ann, would you happen to know if the electron sheds all the extra energy at once, in a single photon, or perhaps over a bit of time in multiple photons?
Also, would you happen to have any idea on just how the extra energy was formed into a photon?

[Chris Peterson]

Ann, would you happen to know if the electron sheds all the extra energy at once, in a single photon, or perhaps over a bit of time in multiple photons?

Each time an electron drops to a lower energy state, a photon is emitted. This is often a cascade of events, each producing different wavelength photons. H-alpha is usually produced when a free electron rejoins a hydrogen nucleus. If it drops from n=3 to n=2, an H-a photon is produced. Other transitions produce different wavelengths. After an n=3 to n=2 transition, you might have a n=2 to n=1 transition, producing a Lyman-alpha (121.6 nm UV) photon.

Also, would you happen to have any idea on just how the extra energy was formed into a photon?

A photon is the quantum of electromagnetic energy. It is, essentially, pure energy.

[Beyond]

A photon is the quantum of electromagnetic energy. It is, essentially, pure energy.

Ok, a photon is pure energy. So how does that little bit of energy get and keep it's shape? It's not like it's sort of gooey and cut out like a cookie is cut out of dough by a cookie cutter and then baked, so it retains it's shape, until it's munched on, that is.