APOD: NGC 7023: The Iris Nebula (2023 Sep 02)

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APOD: NGC 7023: The Iris Nebula (2023 Sep 02)

Post by APOD Robot » Sat Sep 02, 2023 4:06 am

Image NGC 7023: The Iris Nebula

Explanation: These cosmic clouds have blossomed 1,300 light-years away in the fertile starfields of the constellation Cepheus. Called the Iris Nebula, NGC 7023 is not the only nebula to evoke the imagery of flowers. Still, this deep telescopic image shows off the Iris Nebula's range of colors and symmetries embedded in surrounding fields of interstellar dust. Within the Iris itself, 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 reflection nebula glow with a faint reddish photoluminescence as some dust grains effectively convert the star's invisible ultraviolet radiation to visible red light. Infrared observations indicate that this nebula contains complex carbon molecules known as PAHs. The dusty blue petals of the Iris Nebula span about six light-years.

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Re: APOD: NGC 7023: The Iris Nebula (2023 Sep 02)

Post by Ann » Sat Sep 02, 2023 5:40 am

Oh beautiful beautiful Iris Nebula! :D And today's APOD is lovely!


I wish I had more time to write more about this nebula. But I have very little time, so I'll just say that the central star of the Iris Nebula, HD 200775, is spectral class B2V. This spectral class is ideal for creating blue reflection nebulas (in the presence of dust, of course). Stars of spectral class B2 emit "the maximum amount of blue light for not emitting enough ultraviolet light to ionize a red emission nebula".

Check out this list of stellar characteristics. According to the list, the typical temperature of B2V stars is 21,000 K, whereas the typical temperature of stars of spectral class B1V is 23,000 K.

Rho Ophiuchi is the central star of a famous blue reflection nebula that is one of the brightest and largest in the sky. Guess what spectral class its central star is?


Of course! Its B2V!

The brightest blue reflection nebula in the sky is considered to be M78 in Orion.


The central star of M78 is HD 38563. Its spectral class is... no, not B2V, but B2III.

So what happens if the central star of a nebula is spectral class B1V? Well, then you get a small faint red emission nebula! You get the Cocoon Nebula!


I really like this picture of the Cocoon Nebula by Marcel Drechsler:


You can see all the blue reflection nebulosity surrounding the pink center, and you can see beige dust and interstellar red hydrogen alpha light (which may of may not come from the central star of the Cocoon Nebula). And you can see, above all, that a spectral class of B1 is what it takes, at least, to create a red emission nebula.

The central star of the Cocoon Nebula, by the way, doesn't even have an HD designation, and is know as BD +46 3474. It is indeed spectral class B1V.

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Re: APOD: NGC 7023: The Iris Nebula (2023 Sep 02)

Post by emc » Sat Sep 02, 2023 10:50 am

Ann wrote: Sat Sep 02, 2023 5:40 am Oh beautiful beautiful Iris Nebula! :D And today's APOD is lovely!


I wish I had more time to write more about this nebula.

Ann
Your time is much appreciated! Thanks. I learn I enjoy!

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Re: APOD: NGC 7023: The Iris Nebula (2023 Sep 02)

Post by AVAO » Sat Sep 02, 2023 5:57 pm

APOD Robot wrote: Sat Sep 02, 2023 4:06 am Image NGC 7023: The Iris Nebula

Congratulation to Lorand Fenyes for this great APOD.
And congratulation, you also found a new super fast running star!
...this is yours..;-)

Click to view full size image 1 or image 2
DSS2 and todays APOD
Image Credit & Copyright: Lorand Fenyes
2MASS 21011068+6807556 RAJ2000 315.294506 DEJ2000 +68.132133
DR3Name Gaia DR3 2270239585757069312 RAdeg 315.29464042437 DEdeg 68.13163260733
Last edited by AVAO on Sat Sep 02, 2023 6:15 pm, edited 1 time in total.

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Re: APOD: NGC 7023: The Iris Nebula (2023 Sep 02)

Post by AVAO » Sat Sep 02, 2023 6:11 pm

Ann wrote: Sat Sep 02, 2023 5:40 am
...
I wish I had more time to write more about this nebula. But I have very little time, so I'll just say that the central star of the Iris Nebula, HD 200775, is spectral class B2V. This spectral class is ideal for creating blue reflection nebulas (in the presence of dust, of course). Stars of spectral class B2 emit "the maximum amount of blue light for not emitting enough ultraviolet light to ionize a red emission nebula".
...

Ann
ThanX Ann for your great explanations - as always.

I like the Iris Nebula in IR too
... and I'm already looking forward to a future picture of JWST :roll:
Closeup NGC 7023 jac berne (flickr) Original Data Source: NASA/ESA (SST)
bigg: https://live.staticflickr.com/65535/531 ... 4a08_o.jpg


and a nice feature :evil: from HST-IR: HH_XXX (J3150526.05+681306.57)
jac berne (flickr) Original Data Source: NASA/ESA (HST)

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Re: APOD: NGC 7023: The Iris Nebula (2023 Sep 02)

Post by johnnydeep » Sat Sep 02, 2023 8:03 pm

The details of this image say it was made using a "206/1620 lens binoculars". Binoculars? And could this really be a binocular with two objective lenses each with a 206 mm diameter?
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Re: APOD: NGC 7023: The Iris Nebula (2023 Sep 02)

Post by johnnydeep » Sat Sep 02, 2023 8:06 pm

AVAO wrote: Sat Sep 02, 2023 5:57 pm
APOD Robot wrote: Sat Sep 02, 2023 4:06 am Image NGC 7023: The Iris Nebula

Congratulation to Lorand Fenyes for this great APOD.
And congratulation, you also found a new super fast running star!
...this is yours..;-)

Click to view full size image 1 or image 2
DSS2 and todays APOD
Image Credit & Copyright: Lorand Fenyes
2MASS 21011068+6807556 RAJ2000 315.294506 DEJ2000 +68.132133
DR3Name Gaia DR3 2270239585757069312 RAdeg 315.29464042437 DEdeg 68.13163260733
That's cool. These mouse-over displays of two images really serve to highlight differences. How much time passed between the two images?
--
"To B̬̻̋̚o̞̮̚̚l̘̲̀᷾d̫͓᷅ͩḷ̯᷁ͮȳ͙᷊͠ Go......Beyond The F͇̤i̙̖e̤̟l̡͓d͈̹s̙͚ We Know."{ʲₒʰₙNYᵈₑᵉₚ}

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Re: APOD: NGC 7023: The Iris Nebula (2023 Sep 02)

Post by orin stepanek » Sat Sep 02, 2023 8:26 pm

268_lorand_fenyes_iris_ngc7023_1024.jpg
I grow Iris flowers and I love them! I even have a pretty blue one
like the nebula! :D
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Last edited by orin stepanek on Sat Sep 02, 2023 8:28 pm, edited 1 time in total.
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Re: APOD: NGC 7023: The Iris Nebula (2023 Sep 02)

Post by AVAO » Sat Sep 02, 2023 8:28 pm

johnnydeep wrote: Sat Sep 02, 2023 8:06 pm
AVAO wrote: Sat Sep 02, 2023 5:57 pm
APOD Robot wrote: Sat Sep 02, 2023 4:06 am Image NGC 7023: The Iris Nebula

Congratulation to Lorand Fenyes for this great APOD.
And congratulation, you also found a new super fast running star!
...this is yours..;-)

Click to view full size image 1 or image 2
DSS2 and todays APOD
Image Credit & Copyright: Lorand Fenyes
2MASS 21011068+6807556 RAJ2000 315.294506 DEJ2000 +68.132133
DR3Name Gaia DR3 2270239585757069312 RAdeg 315.29464042437 DEdeg 68.13163260733
That's cool. These mouse-over displays of two images really serve to highlight differences. How much time passed between the two images?
Good question. DSS2 was produced between 1996 and 2006. That means there should be 17-27 years between the two pictures...

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Re: APOD: NGC 7023: The Iris Nebula (2023 Sep 02)

Post by emc » Sat Sep 02, 2023 9:08 pm

orin stepanek wrote: Sat Sep 02, 2023 8:26 pm 268_lorand_fenyes_iris_ngc7023_1024.jpg
I grow Iris flowers and I love them! I even have a pretty blue one
like the nebula! :D
😎 Thanks for sharing Orin.
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Re: APOD: NGC 7023: The Iris Nebula (2023 Sep 02)

Post by alter-ego » Sun Sep 03, 2023 12:16 am

AVAO wrote: Sat Sep 02, 2023 8:28 pm
johnnydeep wrote: Sat Sep 02, 2023 8:06 pm
AVAO wrote: Sat Sep 02, 2023 5:57 pm


Congratulation to Lorand Fenyes for this great APOD.
And congratulation, you also found a new super fast running star!
...this is yours..;-)

Click to view full size image 1 or image 2
DSS2 and todays APOD
Image Credit & Copyright: Lorand Fenyes
2MASS 21011068+6807556 RAJ2000 315.294506 DEJ2000 +68.132133
DR3Name Gaia DR3 2270239585757069312 RAdeg 315.29464042437 DEdeg 68.13163260733
That's cool. These mouse-over displays of two images really serve to highlight differences. How much time passed between the two images?
Good question. DSS2 was produced between 1996 and 2006. That means there should be 17-27 years between the two pictures...
Based on GAIA pm data for this star, I calculate the time difference to be ~23 years.
• There is a large proper motion in declination. Proper motion in RA and Dec = 5.6 mas/yr and 101 mas/yr respectively, or a total pm ≈ 102 mas/yr
• The angular change ≈ 2.3 arcseconds
→ 2.3 arcseconds ÷ 0.1 arcseconds/yr = 23 years
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Re: APOD: NGC 7023: The Iris Nebula (2023 Sep 02)

Post by Ann » Sun Sep 03, 2023 4:31 am

AVAO wrote: Sat Sep 02, 2023 5:57 pm
APOD Robot wrote: Sat Sep 02, 2023 4:06 am Image NGC 7023: The Iris Nebula

Congratulation to Lorand Fenyes for this great APOD.
And congratulation, you also found a new super fast running star!
...this is yours..;-)

Click to view full size image 1 or image 2
DSS2 and todays APOD
Image Credit & Copyright: Lorand Fenyes
2MASS 21011068+6807556 RAJ2000 315.294506 DEJ2000 +68.132133
DR3Name Gaia DR3 2270239585757069312 RAdeg 315.29464042437 DEdeg 68.13163260733
What a fascinating discovery, AVAO (and Lorand Fenyes)!

And thank you, too, for the other, fascinating pictures you posted in another of your posts.

Your pictures are always great! Thank you for posting them here!

Ann
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Re: APOD: NGC 7023: The Iris Nebula (2023 Sep 02)

Post by Ann » Sun Sep 03, 2023 4:50 am

alter-ego wrote: Sun Sep 03, 2023 12:16 am
AVAO wrote: Sat Sep 02, 2023 8:28 pm
johnnydeep wrote: Sat Sep 02, 2023 8:06 pm

That's cool. These mouse-over displays of two images really serve to highlight differences. How much time passed between the two images?
Good question. DSS2 was produced between 1996 and 2006. That means there should be 17-27 years between the two pictures...
Based on GAIA pm data for this star, I calculate the time difference to be ~23 years.
• There is a large proper motion in declination. Proper motion in RA and Dec = 5.6 mas/yr and 101 mas/yr respectively, or a total pm ≈ 102 mas/yr
• The angular change ≈ 2.3 arcseconds
→ 2.3 arcseconds ÷ 0.1 arcseconds/yr = 23 years
Thanks, alter-ego, I'm so impressed by your skills in math! Thanks for using it here at Starship Asterisk* to help us understand things that have to do with APODs!

You have apparently identified the "flying star". I used Simbad to try to identify it, to get a designation for it, but I failed. All I got was the star next to it (to the west of it), 2MASS J21010772+6808005.

Did you get a designation for the fast moving star? How else could you get a proper motion for it?

In order to know the star's proper motion we need to know its true distance, right? Oh, you just calculated its displacement across the sky between the two images, right?

No, wait, you used Gaia! How did you do that? I have never used Gaia to try to find a star!

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Re: APOD: NGC 7023: The Iris Nebula (2023 Sep 02)

Post by VictorBorun » Sun Sep 03, 2023 6:38 am

do I get it right:
this is a dust cloud
dimly backlighted by many distant stars, as can be seen at the edges of this APOD frame (and showing dark gray with a brown tint)
brightly backlighted by a single star closely behind the dust cloud (in pale cyan to blue to deep violet as the angle of scattering grows)
glowing as red ashes, over the bright illumination, — which we can't see on earth in the sunny day but here the dust is heated with a UV-bright star, making thermal red glow of the carbon dust bright enough to be seen

lorandfenyes

Re: APOD: NGC 7023: The Iris Nebula (2023 Sep 02)

Post by lorandfenyes » Sun Sep 03, 2023 7:59 am

Ann wrote: Sun Sep 03, 2023 4:31 am
AVAO wrote: Sat Sep 02, 2023 5:57 pm
APOD Robot wrote: Sat Sep 02, 2023 4:06 am Image NGC 7023: The Iris Nebula

Congratulation to Lorand Fenyes for this great APOD.
And congratulation, you also found a new super fast running star!
...this is yours..;-)

Click to view full size image 1 or image 2
DSS2 and todays APOD
Image Credit & Copyright: Lorand Fenyes
2MASS 21011068+6807556 RAJ2000 315.294506 DEJ2000 +68.132133
DR3Name Gaia DR3 2270239585757069312 RAdeg 315.29464042437 DEdeg 68.13163260733
What a fascinating discovery, AVAO (and Lorand Fenyes)!

And thank you, too, for the other, fascinating pictures you posted in another of your posts.

Your pictures are always great! Thank you for posting them here!

Ann
Wov, thank you it is very-very interesting.

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Re: APOD: NGC 7023: The Iris Nebula (2023 Sep 02)

Post by emc » Sun Sep 03, 2023 9:28 am

orin stepanek wrote: Sat Sep 02, 2023 8:26 pm 268_lorand_fenyes_iris_ngc7023_1024.jpg
I grow Iris flowers and I love them! I even have a pretty blue one
like the nebula! :D
I finally got your joke but I had to visit your Flowers Around the House thread to get it. You funny Orin! :mrgreen: Me slow! :mrgreen:
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lorandfenyes

Re: APOD: NGC 7023: The Iris Nebula (2023 Sep 02)

Post by lorandfenyes » Sun Sep 03, 2023 10:50 am

johnnydeep wrote: Sat Sep 02, 2023 8:03 pm The details of this image say it was made using a "206/1620 lens binoculars". Binoculars? And could this really be a binocular with two objective lenses each with a 206 mm diameter?
The site is in Hungarian, you've probably been tricked by the Google translator. An Astro-Physics Starfire 206 EDF is the astronomical telescope with which the picture was taken.

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Re: APOD: NGC 7023: The Iris Nebula (2023 Sep 02)

Post by johnnydeep » Sun Sep 03, 2023 12:53 pm

lorandfenyes wrote: Sun Sep 03, 2023 10:50 am
johnnydeep wrote: Sat Sep 02, 2023 8:03 pm The details of this image say it was made using a "206/1620 lens binoculars". Binoculars? And could this really be a binocular with two objective lenses each with a 206 mm diameter?
The site is in Hungarian, you've probably been tricked by the Google translator. An Astro-Physics Starfire 206 EDF is the astronomical telescope with which the picture was taken.
Thanks. Yup, google (or the built-in Vivaldi browser translator) it was. Those Starfire 206 EDFs are apparently pretty rare. So I guess I'll just have to settle for one of these beauts instead:

Last edited by johnnydeep on Sun Sep 03, 2023 12:56 pm, edited 1 time in total.
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Re: APOD: NGC 7023: The Iris Nebula (2023 Sep 02)

Post by johnnydeep » Sun Sep 03, 2023 12:55 pm

Ann wrote: Sun Sep 03, 2023 4:50 am
alter-ego wrote: Sun Sep 03, 2023 12:16 am
AVAO wrote: Sat Sep 02, 2023 8:28 pm

Good question. DSS2 was produced between 1996 and 2006. That means there should be 17-27 years between the two pictures...
Based on GAIA pm data for this star, I calculate the time difference to be ~23 years.
• There is a large proper motion in declination. Proper motion in RA and Dec = 5.6 mas/yr and 101 mas/yr respectively, or a total pm ≈ 102 mas/yr
• The angular change ≈ 2.3 arcseconds
→ 2.3 arcseconds ÷ 0.1 arcseconds/yr = 23 years
Thanks, alter-ego, I'm so impressed by your skills in math! Thanks for using it here at Starship Asterisk* to help us understand things that have to do with APODs!

You have apparently identified the "flying star". I used Simbad to try to identify it, to get a designation for it, but I failed. All I got was the star next to it (to the west of it), 2MASS J21010772+6808005.

Did you get a designation for the fast moving star? How else could you get a proper motion for it?

In order to know the star's proper motion we need to know its true distance, right? Oh, you just calculated its displacement across the sky between the two images, right?

No, wait, you used Gaia! How did you do that? I have never used Gaia to try to find a star!

Ann
And even more importantly, how fast does this mean the star is actually moving in km/s?
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"To B̬̻̋̚o̞̮̚̚l̘̲̀᷾d̫͓᷅ͩḷ̯᷁ͮȳ͙᷊͠ Go......Beyond The F͇̤i̙̖e̤̟l̡͓d͈̹s̙͚ We Know."{ʲₒʰₙNYᵈₑᵉₚ}

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Re: APOD: NGC 7023: The Iris Nebula (2023 Sep 02)

Post by Nitin Khuthia » Sun Sep 03, 2023 5:10 pm

this is my first post and as i cant find any place to start or join discussion i am using this. please guide me to right place if this not. my apologies beforehand.
with reference to the explanation
" the star's invisible ultraviolet radiation to visible red light. I"
i believe the nearest spectrum to ultraviolet is violet and not red so is it actually ultraviolet is converted to red or infrared converted to red?
if there is some mistake it may be corrected.
thanks

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Re: APOD: NGC 7023: The Iris Nebula (2023 Sep 02)

Post by Chris Peterson » Sun Sep 03, 2023 5:15 pm

Nitin Khuthia wrote: Sun Sep 03, 2023 5:10 pm this is my first post and as i cant find any place to start or join discussion i am using this. please guide me to right place if this not. my apologies beforehand.
with reference to the explanation
" the star's invisible ultraviolet radiation to visible red light. I"
i believe the nearest spectrum to ultraviolet is violet and not red so is it actually ultraviolet is converted to red or infrared converted to red?
if there is some mistake it may be corrected.
thanks
It is UV driven photoluminescence. High energy UV light is causing atoms in the dust to re-emit red light. It's the same principle as the way fluorescent inks and paints "glow in the dark" when hit with "black lights" (UV light sources).
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Re: APOD: NGC 7023: The Iris Nebula (2023 Sep 02)

Post by johnnydeep » Sun Sep 03, 2023 5:37 pm

Chris Peterson wrote: Sun Sep 03, 2023 5:15 pm
Nitin Khuthia wrote: Sun Sep 03, 2023 5:10 pm this is my first post and as i cant find any place to start or join discussion i am using this. please guide me to right place if this not. my apologies beforehand.
with reference to the explanation
" the star's invisible ultraviolet radiation to visible red light. I"
i believe the nearest spectrum to ultraviolet is violet and not red so is it actually ultraviolet is converted to red or infrared converted to red?
if there is some mistake it may be corrected.
thanks
It is UV driven photoluminescence. High energy UV light is causing atoms in the dust to re-emit red light. It's the same principle as the way fluorescent inks and paints "glow in the dark" when hit with "black lights" (UV light sources).
And in response to the OP's question about the most appropriate place to post about this particular APOD, this is indeed the place! Not sure how the OP arrived here, but the "Discuss" link at the bottom of the APOD page will take you here.
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Re: APOD: NGC 7023: The Iris Nebula (2023 Sep 02)

Post by Ann » Sun Sep 03, 2023 5:58 pm

Nitin Khuthia wrote: Sun Sep 03, 2023 5:10 pm this is my first post and as i cant find any place to start or join discussion i am using this. please guide me to right place if this not. my apologies beforehand.
with reference to the explanation
" the star's invisible ultraviolet radiation to visible red light. I"
i believe the nearest spectrum to ultraviolet is violet and not red so is it actually ultraviolet is converted to red or infrared converted to red?
if there is some mistake it may be corrected.
thanks
It works something like this.

The hydrogen atom consists of a proton and an electron that moves around the proton in "electron shells" that represent different energy levels.



Note!! This is a very simplified model of the hydrogen atom!

Anyway. The electron "prefers" the lowest-energy electron shell. But if the hydrogen atom is hit by a high-energy photon of ultraviolet light, the electron can be knocked into a higher electron shell.



But the electron will not stay in the higher electron shell. It will soon fall back to its lower electron shell again. But in order to do so, it has to shed the extra energy that it gained when it was knocked into the higher electron shell. Usually, it does so by emitting a photon of 656 nm, which is the red light of hydrogen alpha.

Sometimes the electron is knocked into even higher electron shells, and then it will emit a photon of a "bluer" wavelength as it falls down:



So when the electron is knocked "two shells up" it emits a cyan-colored photon of 486 nm as it falls down, which corresponds to hydrogen beta. Hydrogen gamma corresponds to a blue photon of 434 nm, and it is emitted when the electron falls down after having been knocked "three shells up". Hydrogen delta is a violet photon of 410 nm.


The Lagoon Nebula is a typical emission nebula, where very hot O-type stars emit torrents of ultraviolet photons which strike large numbers of hydrogen atoms and ionize them, which means that the electrons of the ionized hydrogen are knocked "one or more" levels up. As the electrons fall down again, they emit primarily red light of hydrogen alpha at 656 nm. However, and particularly closer to the hot stars, a number of electrons will be knocked "two levels up" and will emit cyan light of 486 nm as they fall down. (Occasionally some electrons will be knocked three or four levels up and emit blue or violet light, but this is rare.) The combination of 656 nm photons and 486 nm photons gives many emission nebulas a pink hue. In the case of the Lagoon Nebula, blue starlight from the hot stars will be reflected in dust grains in the nebula in the same way as in the Iris Nebula, which will add still more blue light to the inner Lagoon Nebula.

(As for the Lyman series, I haven't taken an interest in it, and I'm not prepared to talk about it. But the Lyman series is all about high-energy electrons emitting invisible high-energy ultraviolet photons.)

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Re: APOD: NGC 7023: The Iris Nebula (2023 Sep 02)

Post by johnnydeep » Sun Sep 03, 2023 6:49 pm

In response to Ann's explanation of electrons changing quantum orbits, why is it that a high energy photon can raise an electron into a higher orbit, but it can emit a lower energy photon to transition back down to a lower orbit? Does that only happen if the electron steps down in orbital stages, which requires a less energetic photon to be emitted at each step down, but the sum total of energy of the photons emitted would still add up to the energy of the initial photon that raised the orbit multiple levels?
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Location: Nebraska

Re: APOD: NGC 7023: The Iris Nebula (2023 Sep 02)

Post by orin stepanek » Sun Sep 03, 2023 7:20 pm

emc wrote: Sun Sep 03, 2023 9:28 am
orin stepanek wrote: Sat Sep 02, 2023 8:26 pm 268_lorand_fenyes_iris_ngc7023_1024.jpg
I grow Iris flowers and I love them! I even have a pretty blue one
like the nebula! :D
I finally got your joke but I had to visit your Flowers Around the House thread to get it. You funny Orin! :mrgreen: Me slow! :mrgreen:
Hi; I really do grow Iris; And I love the Iris Nebula! To me The Iris is an orchid; as it is a very delicate flower! I'll try to get a photo of it when it is in bloom. I have been having trouble downloading photos from my Canon 100 lately, but by the time the orchids are in bloom I should get it figured out! 😎
Orin

Smile today; tomorrow's another day!