APOD: The Lagoon Nebula in Hydrogen, and... (2016 Jan 05)

[APOD Robot]

The Lagoon Nebula in Hydrogen, Sulfur, and Oxygen

Explanation: The majestic Lagoon Nebula is filled with hot gas and the home for many young stars. Spanning 100 light years across while lying only about 5000 light years distant, the Lagoon Nebula is so big and bright that it can be seen without a telescope toward the constellation of the Archer (Sagittarius). Many bright stars are visible from NGC 6530, an open cluster that formed in the nebula only several million years ago. The greater nebula, also known as M8 and NGC 6523, is named "Lagoon" for the band of dust seen to the right of the open cluster's center. The featured image was taken in the light emitted by Hydrogen (shown in brown), Sulfur (red), and Oxygen (blue) and displayed in enhanced color. The featured picture is a newly processed panorama of M8, capturing twice the diameter of the Full Moon. Star formation continues in the Lagoon Nebula as witnessed by the many globules that exist there.

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[/b]

[old dude]

There's a scary alien at the end of this tunnel, and it refuses to fit in 900 pixels.

https://i.imgur.com/R35iCc0.jpg

[Boomer12k]

There's a scary alien at the end of this tunnel, and it refuses to fit in 900 pixels.

https://i.imgur.com/R35iCc0.jpg

Yes....Gnashing teeth and a Blaring eye, and Tentacles... "The Thing from The Lagoon"...1958 sci-fi movie I think...

:---[===] *

[Boomer12k]

Mesmerizing...

It never fails to amaze me....OXYGEN...

I wonder what an H.S.O. image of our area of space would look like....hmmmmm...

:---[===] *

[Chris Peterson]

Mesmerizing...

It never fails to amaze me....OXYGEN...

I wonder what an H.S.O. image of our area of space would look like....hmmmmm...

Pretty dull, since all of these are largely absent.

[jandomc]

How about nitrogen?

[Chris Peterson]

How about nitrogen?

There is certainly nitrogen present in this nebula. However, the predominant emission lines of nitrogen are only 11 nm from that of hydrogen. So it requires very narrow band filters to isolate the two (and in ordinary color images, we are unable to distinguish hydrogen and nitrogen, both being simply red).

[BMAONE23]

There's a scary alien at the end of this tunnel, and it refuses to fit in 900 pixels.

https://i.imgur.com/R35iCc0.jpg

Yes....Gnashing teeth and a Blaring eye, and Tentacles... "The Thing from The Lagoon"...1958 sci-fi movie I think...

:---[===] *

Rotate it 180 and you have an almost purrrrfect cosmic cat

[DavidLeodis]

How any nebula came to be so named can be very confusing and the Lagoon Nebula is (to me) no exception. In the explanation it states the nebula "is named "Lagoon" for the band of dust seen to the right of the open cluster's center". I assume the open cluster is the group of stars towards the top in the image but I don't see an obvious band of dust to its right (there is a dark patch which is presumably one of the globules). I would be grateful if someone could please inform me where that band of dust is.

If I had ever been asked to name the nebula I doubt that naming it after a lagoon would have ever crossed my mind!

[Chris Peterson]

How any nebula came to be so named can be very confusing and the Lagoon Nebula is (to me) no exception. In the explanation it states the nebula "is named "Lagoon" for the band of dust seen to the right of the open cluster's center". I assume the open cluster is the group of stars towards the top in the image but I don't see an obvious band of dust to its right (there is a dark patch which is presumably one of the globules). I would be grateful if someone could please inform me where that band of dust is.

If I had ever been asked to name the nebula I doubt that naming it after a lagoon would have ever crossed my mind! :?

Obviously, there's a fair degree of pareidolia involved in the naming of most nebulas. Also, keep in mind that these objects which have names going back many decades all received those names based on visual telescopic views, where every single nebula looks like a fuzzy gray patch, usually showing nothing more than a faint shape and possibly some barely discernible structure created by dust lanes. In many ways, that makes it easier to give them simple names (in contrast to the fantastically detailed telescopic images we're used to today, where we see comments like "does anybody else see that red and green parrot sitting on a pirates shoulder down in the lower left section?")

[Ann]

How any nebula came to be so named can be very confusing and the Lagoon Nebula is (to me) no exception. In the explanation it states the nebula "is named "Lagoon" for the band of dust seen to the right of the open cluster's center". I assume the open cluster is the group of stars towards the top in the image but I don't see an obvious band of dust to its right (there is a dark patch which is presumably one of the globules). I would be grateful if someone could please inform me where that band of dust is.

If I had ever been asked to name the nebula I doubt that naming it after a lagoon would have ever crossed my mind!

The band of dust is rather obvious in this image. The Lagoon is the round red shape inside the dark dust band.

Click to view full size image

Artist's impression of a lagoon in the Hudson River.
Source: http://www.popularmechanics.com/science ... -16931996/

Ann

[neufer]

Also, keep in mind that these objects which have names going back many decades all received those names based on visual telescopic views, where every single nebula looks like a fuzzy gray patch, usually showing nothing more than a faint shape and possibly some barely discernible structure created by dust lanes. In many ways, that makes it easier to give them simple names (in contrast to the fantastically detailed telescopic images we're used to today, where we see comments like "does anybody else see that red and green parrot sitting on a pirates shoulder down in the lower left section?")

[b][color=#0000FF]M17: The Omega (or Swan, or Horseshoe, or Lobster, or Checkmark) Nebula[/color][/b]

---

They probably almost all received those names based on subjective responses to a variety of ambiguous visual telescopic drawings of nebula.

<<An inkblot test is a personality test which involves the evaluation of a subjects response to ambiguous ink blots. This test was published in 1921 by Hermann Rorschach who was a psychiatrist from Switzerland. Throughout the 1940s and 1950s the ink blot test was popular among clinical psychologists but quickly lost popularity as critics claimed it to be too subjective.>>

---------------------------------------------------------
List of Common Names for Messier Objects
compiled by Hartmut Frommert
==============================
M1 "The Crab Nebula" (Rosse 1844)

M6 "Butterfly cluster"
(`Splendors of the Heavens', Phillips/Steaphenson 1923)

M7 "Ptolemy's cluster" (Ptolemy mentioned it 138 AD, hf)

M8 "The Lagoon Nebula".
Its center contains "The Hourglass Nebula" (A.D. Thackeray 1956).
A part of M8 was named Dragon Nebula (Sky Catalog 2000).

M11 "The Wild Duck Cluster" (Smyth)

M13 "Great Hercules Globular Cluster" (I admit: not very original )

M16 associated with the "Eagle Nebula" or "Star Queen Nebula" (IC 4703)

M17 "The Omega (or Swan, or Horseshoe, or Lobster, or Checkmark) Nebula"
(thanks to Steve Mencinsky for contributing the "Lobster", a common
name for M17 on the Southern hemisphere)

M20 "The Trifid Nebula"

M24 "Sagittarius Star Cloud" or "Delle Caustiche".
Milky Way Patch containing open cluster NGC 6603,

M27 "The Dumbbell Nebula", "Diablo Nebula", "Double-Headed Shot"
(latter two contributed by Jeff Bondono, also in Sky Catalog 2000),
"Apple Core" (J.R. Freeman)

M31 "The Andromeda Galaxy"

M33 "The Triangulum Galaxy" (also "Pinwheel")
Pinwheel alternatively (and perhaps more commonly) applied to M101,
but Burnham has this name for M33. The RASC Observer's Handbook also
lists M99 under the name "Pinwheel".
One might take "Triangulum Pinwheel" for M33 to distinguish.
J.R. Freeman reports that he has occasionally heard "Maytag Galaxy",
an American joke, as the Whirlpool Galaxy M51 and M33 are both gorgeous
face-on spirals, and "Whirlpool" and "Maytag" are both washing machines.

M42 The Great Orion Nebula, contains the "Trapezium Cluster"

M43 "de Mairan's nebula" (NGC), part of the Orion Nebula

M44 Praesepe, Manger, the Beehive Cluster

M45 Subaru, the Pleiades--the Seven Sisters

M51 "The Whirlpool Galaxy", Lord Rosse's "Question Mark"

M57 "The Ring Nebula"

M63 "The Sunflower galaxy"

M64 "The Blackeye galaxy", "Sleeping Beauty Galaxy"

M65 forms the "Leo Triplet" with M66 and NGC 3628

M66 forms the "Leo Triplet" with M65 and NGC 3628

M76 is cited with 3 common names:
1. "The Little Dumbbell Nebula" (most common, e.g. Sky Catalogue 2000)
2. "The Cork Nebula" (e.g. Burnham)
3. "The Butterfly Nebula" (e.g. a CFHT slide set I got from
Hansen Planetarium some time ago).
All 3 can be motivated by its appearance in different
aperture telescopes, with different filters, and on photos
with different exposure times.
4. "The Barbell Nebula"
5. "The Apple Core Nebula" is the name Mike Frazier proposes for it.
NB: This object seems to attract names like no other: It has also two
NGC numbers: 650 and 651.

M81 is sometimes called "Bode's Nebula" (Murdin/Allen/Malin 1979) or better,
"Bode's Galaxy".

M82 "The Cigar Galaxy" (brought to my attention by Tom Polakis)

M83 "The Southern Pinwheel Galaxy"

M87 "Virgo A" is in the center of the Virgo cluster
its active center is called "The Smoking Gun" (Nasa/STScI)

M97 "The Owl Nebula"

M99 This beautiful spiral galaxy is referred to by two "Wheel" names:
1. "St. Katherine's Wheel"
[Francis Jacob (1895) - thanks to Bob McGown and Dareth Murray
for communicating]
2. "The Pinwheel Galaxy"
[RASC Observer's Handbook]
As this name applies also to M101 (preferably) and M33 (sometimes),
a modified version like "Coma Pinwheel" or "Virgo Cluster Pinwheel"
might help to distinguish.

M101 "The Pinwheel Galaxy"
[Murdin/Allen/Malin 1979, Sky Catalogue 2000, RASC Observer's Handbook]
(this name shared with M33, but perhaps more commonly for M101.
The RASC Observer's Handbook also lists M99 under the name "Pinwheel")

M102[?]=NGC 5866 "The Spindle Galaxy" (hf, Sky&Telescope 7/95 p. 51).
Shares the name "spindle" with NGC 3115.

M104 "The Sombrero Galaxy"
---------------------------------------------------------

[DavidLeodis]

Thanks all for your help with my query about why M8/NGC 6523 was named the Lagoon Nebula. The naming of nebulae is clearly a very fuzzy (or should I say very nebulous ) area.

As to the it "is named "Lagoon" for the band of dust seen to the right of the open cluster's center" I'm still confused, as don't see an obvious band there. It's surely not the 'swan-like' globule. The only obvious band that I readily see in the image is that stretching down from right to left below what I assume is the open cluster. I now wonder if the explanation wording is correct?

[BMAONE23]

There's a scary alien at the end of this tunnel, and it refuses to fit in 900 pixels.

https://i.imgur.com/R35iCc0.jpg

Yes....Gnashing teeth and a Blaring eye, and Tentacles... "The Thing from The Lagoon"...1958 sci-fi movie I think...

:---[===] *

Rotate it 180 and you have an almost purrrrfect cosmic cat

Here is the cosmic kitty

[Ron-Astro Pharmacist]

That looks more like a creature from the Blue Lagoon.

And this one might be the worst of its kind.

Click to play embedded YouTube video.

[Ann]

Thanks all for your help with my query about why M8/NGC 6523 was named the Lagoon Nebula. The naming of nebulae is clearly a very fuzzy (or should I say very nebulous ) area.

As to the it "is named "Lagoon" for the band of dust seen to the right of the open cluster's center" I'm still confused, as don't see an obvious band there. It's surely not the 'swan-like' globule. The only obvious band that I readily see in the image is that stretching down from right to left below what I assume is the open cluster. I now wonder if the explanation wording is correct?

That is indeed the dust band in question.

It is harder to spot the dust band in a narrowband image, like this APOD, than it is in an RGB image, like the one I provided a link to. In an RGB image, the dust band is an obvious dark band crossing an almost uniformly red nebula. In this APOD, so many features can be seen in the nebula that the dust band becomes less obvious.

Like you, I think the wording in the caption is wrong. The dust band is not "to the right of the open cluster's center". That's because the image has been rotated, I think. The way it is presented in the APOD, north isn't up, as I would expect it to be, because it's customary.

Take a look of this APOD from 2013 of the Lagoon Nebula. Here north is up, and you can see that the dust band is indeed to the right of the open cluster's center.

Thanks for the kitty, BMAONE! I had never seen that one before.

Ann

[StarObs]

From the caption of the picture, one can think that there is a lot of Oxygen in the inner part of the nebula, and more Sulphur in the outer part. Is this correct?

[Ann]

From the caption of the picture, one can think that there is a lot of Oxygen in the inner part of the nebula, and more Sulphur in the outer part. Is this correct?

That's correct. Oxygen emission is typically found near very hot and energetic sources, because oxygen emission (OIII) represents a very high level of ionization. At the same time, you don't find oxygen emission in thick dust clouds. OIII emission is found in very rarefied parts of nebulas near high-energetic sources.

Sulphur emission (SII) represents a much lower level of emission, so we find it much farther away from the hot energetic sources.

Ann

[starsurfer]

From the caption of the picture, one can think that there is a lot of Oxygen in the inner part of the nebula, and more Sulphur in the outer part. Is this correct?

That's correct. Oxygen emission is typically found near very hot and energetic sources, because oxygen emission (OIII) represents a very high level of ionization. At the same time, you don't find oxygen emission in thick dust clouds. OIII emission is found in very rarefied parts of nebulas near high-energetic sources.

Sulphur emission (SII) represents a much lower level of emission, so we find it much farther away from the hot energetic sources.

Ann

Another interesting thing about OIII emission is that it is affected more by dust extinction than Ha. So maybe there are some nebulae that have OIII emission but the light is blocked by dust between us and the nebula.

[Chris Peterson]

From the caption of the picture, one can think that there is a lot of Oxygen in the inner part of the nebula, and more Sulphur in the outer part. Is this correct?

That's correct. Oxygen emission is typically found near very hot and energetic sources, because oxygen emission (OIII) represents a very high level of ionization. At the same time, you don't find oxygen emission in thick dust clouds. OIII emission is found in very rarefied parts of nebulas near high-energetic sources.

Sulphur emission (SII) represents a much lower level of emission, so we find it much farther away from the hot energetic sources.

Well, maybe. But there's a difference between there being more of some element in a particular place, and there being more of an ionized element that is emitting some particular color. In a nebula, you have both a degree of physical separation, and also different areas with the right energy environment to produce obvious emission lines. The actual elements are probably more distributed than they appear when we can only see them in certain ionized forms.

[Ann]

Chris wrote:
...there's a difference between there being more of some element in a particular place, and there being more of an ionized element that is emitting some particular color. In a nebula, you have both a degree of physical separation, and also different areas with the right energy environment to produce obvious emission lines. The actual elements are probably more distributed than they appear when we can only see them in certain ionized forms.

I meant to say that ionized oxygen (OIII) is differently distributed than ionized sulphur (SII) in a typical emission nebula. Of course a picture produced with filters designed to pick up certain emission lines from certain ionized elements doesn't say anything about the distribution of these elements in their neutral form, or their distributions in other forms of ionization.

But my post was ambiguous, so thanks for setting me straight, Chris.

Ann