APOD: Molecular Clouds in the Carina Nebula (2019 Oct 02)

[APOD Robot]

Molecular Clouds in the Carina Nebula

Explanation: They are not alive -- but they are dying. The unusual forms found in the Carina nebula, a few of which are featured here, might best be described as evaporating. Energetic light and winds from nearby stars are breaking apart the dark dust grains that make the iconic forms opaque. Ironically the figures, otherwise known as dark molecular clouds or bright rimmed globules, frequently create in their midst the very stars that later destroy them. The floating space structures pictured here by the orbiting Hubble Space Telescope span a few light months. The Great Nebula in Carina itself spans about 30 light years, lies about 7,500 light years away, and can be seen with a small telescope toward the constellation of Keel(Carina).

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[Ann]

Caterpillar!!! I love it!

And the many-peded thing seems to be looking at a cosmic bunny rabbit in wild flight! Look at the white behind and the two dark hind legs, as the cosmic lepus is trying to get away!

Ann

[AVAO]

Caterpillar!!! I love it!

And the many-peded thing seems to be looking at a cosmic bunny rabbit in wild flight! Look at the white behind and the two dark hind legs, as the cosmic lepus is trying to get away!

Ann

... or Milnesium tardigradum in space (water bear). like it

Click to view full size image

[orin stepanek]

Caterpillar!!! I love it!

And the many-peded thing seems to be looking at a cosmic bunny rabbit in wild flight! Look at the white behind and the two dark hind legs, as the cosmic lepus is trying to get away!

Ann

Kinda; sorta, Looks like the caterpillar has a dog's head sniffing out a fresh scent!

[neufer]

And the many-peded thing seems to be looking at a cosmic bunny rabbit in wild flight!

Look at the white behind and the two dark hind legs, as the cosmic lepus is trying to get away!

---

<<Aplysia dactylomela, the spotted sea hare, is a species of large sea slug, a marine opisthobranch gastropod in the family Aplysiidae, the sea hares. As traditionally defined, this species of sea hare was cosmopolitan, being found in almost all tropical and warm temperate seas, including the Mediterranean Sea where first seen in 2002 and likely self-established due to increasing temperatures.

The colour of the spotted sea hare is very variable, from pale gray to green, to dark brown. There are almost always large black rings on the mantle. The maximum recorded length is 410 mm.

Aplysia dactylomela is commonly found in shallow waters, tide pools and rocky and sandy substrates, they also will be found feeding in beds of sea grass. During the day they will mostly hide under large rocks and in crevices. They usually stay in relatively shallow water, but they have been found as deep as 40 m.

The right giant neuron of Aplysia dactylomela, which is found in the abdominal ganglion, is similar to that of vertebrates, meaning it is ideal for the study of electrophysiology, as well as conditioned-response studies. These neurons have been found to be invaluable in neurological research; the reason for this is that long-lasting effects in neuronal behavior can be detected.

The Aplysia dactylomela is capable of swimming and crawling. It accomplishes the former by creating a funnel using the parapodia folded forward and downwards; this action pulls in water. It then pushes the water out from behind the animal by pressing the anterior parts of the parapodia together, thus forward motion is achieved. The sea hare's usual mode of propulsion is crawling; it crawls by lifting the front end of the foot, stretching it forward then placing it on the ground in front, creating an arching pattern; the remainder of the body follows this arching pattern until the tail is reached.

Like the octopus, the Aplysia dactylomela squirts purple ink if it is disturbed; this ink is an irritant that causes 'altered behaviour' in other invertebrates and fish. Their leathery skin contains toxins which make this sea hare practically inedible to most predators.>>

[Ann]

McloudsCarina_Hubble_1080.jpg

Caterpillar!!! I love it!

And the many-peded thing seems to be looking at a cosmic bunny rabbit in wild flight! Look at the white behind and the two dark hind legs, as the cosmic lepus is trying to get away!

Ann

Kinda; sorta, Looks like the caterpillar has a dog's head sniffing out a fresh scent!

A dog-erpillar!

Ann

[TheZuke!]

I see a dormouse with its tail sticking straight up, just a bit right of the wabbit.

[Ann]

Caterpillar!!! I love it!

And the many-peded thing seems to be looking at a cosmic bunny rabbit in wild flight! Look at the white behind and the two dark hind legs, as the cosmic lepus is trying to get away!

Ann

... or Milnesium tardigradum in space (water bear). like it

Click to view full size image

Perfect, AVAO!

Ann

[Ann]

And the many-peded thing seems to be looking at a cosmic bunny rabbit in wild flight!

Look at the white behind and the two dark hind legs, as the cosmic lepus is trying to get away!

---

<<Aplysia dactylomela, the spotted sea hare, is a species of large sea slug, a marine opisthobranch gastropod in the family Aplysiidae, the sea hares. As traditionally defined, this species of sea hare was cosmopolitan, being found in almost all tropical and warm temperate seas, including the Mediterranean Sea where first seen in 2002 and likely self-established due to increasing temperatures.

The colour of the spotted sea hare is very variable, from pale gray to green, to dark brown. There are almost always large black rings on the mantle. The maximum recorded length is 410 mm.

Aplysia dactylomela is commonly found in shallow waters, tide pools and rocky and sandy substrates, they also will be found feeding in beds of sea grass. During the day they will mostly hide under large rocks and in crevices. They usually stay in relatively shallow water, but they have been found as deep as 40 m.

The right giant neuron of Aplysia dactylomela, which is found in the abdominal ganglion, is similar to that of vertebrates, meaning it is ideal for the study of electrophysiology, as well as conditioned-response studies. These neurons have been found to be invaluable in neurological research; the reason for this is that long-lasting effects in neuronal behavior can be detected.


The Aplysia dactylomela is capable of swimming and crawling. It accomplishes the former by creating a funnel using the parapodia folded forward and downwards; this action pulls in water. It then pushes the water out from behind the animal by pressing the anterior parts of the parapodia together, thus forward motion is achieved. The sea hare's usual mode of propulsion is crawling; it crawls by lifting the front end of the foot, stretching it forward then placing it on the ground in front, creating an arching pattern; the remainder of the body follows this arching pattern until the tail is reached.

Like the octopus, the Aplysia dactylomela squirts purple ink if it is disturbed; this ink is an irritant that causes 'altered behaviour' in other invertebrates and fish. Their leathery skin contains toxins which make this sea hare practically inedible to most predators.>>

Perfectly perfect, Art. And slightly disgusting. Sorry, Aplysia dactylomela, I didn't mean to slight you. You are a marine opisthobranch gastropod sea slug after all, and you are cosmopolitan! That's an impressive pedigree indeed, and you are apparently urbane and cool, too!

Ann

[Cousin Ricky]

Looks like a cross between a dog and a tardigrade to me.

[neufer]

---

• Looks like a cross between a dog and a tardigrade to me.

[orin stepanek]

McloudsCarina_Hubble_1080.jpg

Caterpillar!!! I love it!

And the many-peded thing seems to be looking at a cosmic bunny rabbit in wild flight! Look at the white behind and the two dark hind legs, as the cosmic lepus is trying to get away!

Ann

Kinda; sorta, Looks like the caterpillar has a dog's head sniffing out a fresh scent!

A dog-erpillar!

Ann

Hey! You invented a new creature!

[orin stepanek]

---

• Looks like a cross between a dog and a tardigrade to me.

Magic likes to play peekaboo! I think she would run from a caterpillar!

[dlw]

What causes the bright rims? Seems rather odd.

[neufer]

What causes the bright rims? Seems rather odd.

Young Stellar Objects in Bright Rimmed Clouds
Chelen H. Johnson, Breck School, Minneapolis

<<Stars are born in nebulae, giant molecular clouds of gas and dust found in abundance within disk components of spiral galaxies, including our own. Star formation may be triggered in a molecular cloud by shock waves from a variety of sources including explosion of supernovae, ignition of a very hot nearby star, collisions with another molecular cloud, or density waves within spiral arms. A very large cloud typically contracts to form hundreds (or more) individual stars. During their formation process, protostars are shielded within their nebula, leading to the characterization of nebulae as stellar nurseries. The earliest phases of a protostar’s life are spent deep inside their natal dust cocoon, which absorbs most of the visible radiation produced by the protostar and obscures the protostar from view in the optical. The energy from the protostar warms the dust, which then re-radiates the energy from the protostar as infrared (IR) radiation. Thus, protostars are detectable within their circumstellar material at infrared wavelengths. Jets from hidden protostars may also announce the presence of the still hidden protostar. Bright Rimmed Clouds (BRCs) exist at the edge of HII regions. They are clouds that have experienced compression (and illumination) due to an external ionization shock from nearby massive stars, which served to focus the neutral gas into compact globules (Morgan et al. 2004, Valdetarro et al. 2008) and possibly trigger star formation. Additionally, Morgan (2004) reports that recombination with the ionized boundary layer allows the BRC to be seen at optical wavelengths, hence “bright rimmed.” These clouds generally have a radius of less than 0.5 parsecs, with an average mass about 100 solar masses. Attention has turned to BRCs as potential loci for star formation. Since the ionization front is compressing the gas and dust, the region near the boundary between neutral gas and gas ionized by incident photons is thought to be rich in potential sites for star formation. Sugitani et al. (1991) classify BRCs based on their rim morphology: type A, B, and C with moderately curved, tightly curved, and cometary curved rims, respectively. Using Spitzer’s Infrared Array Camera (IRAC), Allen et al. imaged 32 of the closest BRCs located at estimated distances d < 1.2 kiloparsecs, finding young stellar objects in 75% of the clouds studied.>>

[dlw]

Thanks for that explanation but it begs the question (in my mind) -- why is the illumination just at the edges from our perspective? If the recombination with the ionized boundary layer causes the glow, why doesn't the entire "cloud" appear to glow? Simplistically, it appears that a very bright object is behind the "cloud" which is why we see only the edges illuminated. Sorry to be so dense . . .

[orin stepanek]

Thanks for that explanation but it begs the question (in my mind) -- why is the illumination just at the edges from our perspective? If the recombination with the ionized boundary layer causes the glow, why doesn't the entire "cloud" appear to glow? Simplistically, it appears that a very bright object is behind the "cloud" which is why we see only the edges illuminated. Sorry to be so dense . . .

I don't know ; maybe kinda like this! Probably they are back lit and the thicker part of the cloud dont allow light to go through! Hope this helps!

images.jpg (4.77 KiB) Viewed 7314 times

[dlw]

Yes - that is why I suggested exactly that in my post. However, there are at least 10 "clouds" with glowing edges in that image. It would seem unlikely that each has a bright star directly behind it from our vantage point.

[neufer]

Thanks for that explanation but it begs the question (in my mind) -- why is the illumination just at the edges from our perspective? If the recombination with the ionized boundary layer causes the glow, why doesn't the entire "cloud" appear to glow? Simplistically, it appears that a very bright object is behind the "cloud" which is why we see only the edges illuminated. Sorry to be so dense . . .

The shock has not yet entered & ionized the dark part of the cloud.

[MarkBour]

Thanks for that explanation but it begs the question (in my mind) -- why is the illumination just at the edges from our perspective? If the recombination with the ionized boundary layer causes the glow, why doesn't the entire "cloud" appear to glow? Simplistically, it appears that a very bright object is behind the "cloud" which is why we see only the edges illuminated. Sorry to be so dense . . .

I don't know ; maybe kinda like this! Probably they are back lit and the thicker part of the cloud dont allow light to go through! Hope this helps!

images.jpg

Good pun, there, dlw. And I think your question is quite intelligent. I think an emission nebula (particularly a molecular cloud that is being ionized by nearby sources) might appear brightest around the edges whenever the UV sources are appropriately located. And, if they are not so located, they don't appear to have bright edges. So, here are a few ...

The ring nebula, LHA 120-N 55, NGC 2174, and the Pelican nebula.
(All images just stolen off the net.)

In other words, I agree with orin, I think our caterpildog is actually back- or side-lit.

[neufer]

Thanks for that explanation but it begs the question (in my mind) -- why is the illumination just at the edges from our perspective? If the recombination with the ionized boundary layer causes the glow, why doesn't the entire "cloud" appear to glow? Simplistically, it appears that a very bright object is behind the "cloud" which is why we see only the edges illuminated. Sorry to be so dense . . .

---

I don't know ; maybe kinda like this! Probably they are back lit and the thicker part of the cloud dont allow light to go through! Hope this helps!

Good pun, there, dlw. And I think your question is quite intelligent. I think an emission nebula (particularly a molecular cloud that is being ionized by nearby sources) might appear brightest around the edges whenever the UV sources are appropriately located. And, if they are not so located, they don't appear to have bright edges. So, here are a few ...

The ring nebula, LHA 120-N 55, NGC 2174, and the Pelican nebula.

---

In other words, I agree with orin, I think our caterpildog is actually back- or side-lit.

Click to play embedded YouTube video.

Bright Rimmed Clouds (BRCs) have been studied extensively :

http://asterisk.apod.com/viewtopic.php? ... 55#p295823

"Our caterpildog" is clearly glowing all over his body
but the rim edge concentrates the glow like the edge of a bubble.

• Don't over think this.

[FLPhotoCatcher]

Thanks for that explanation but it begs the question (in my mind) -- why is the illumination just at the edges from our perspective? If the recombination with the ionized boundary layer causes the glow, why doesn't the entire "cloud" appear to glow? Simplistically, it appears that a very bright object is behind the "cloud" which is why we see only the edges illuminated. Sorry to be so dense . . .

The shock has not yet entered & ionized the dark part of the cloud.

The glowing around the clouds are not caused by shock waves or supernova remnants, just starlight.
As for dlw's question, the illumination is not just at the edges, but most easily seen there, due to our line of sight being longer through the thin glowing gas around the clouds. You can see some glowing in front of the biggest cloud (and some other clouds), but your eye may incorrectly interpret that as thinner areas in the cloud allowing light to pass through.

[Boomer12k]

The "Reindeer Rat-thingy" nebula...

I think a better term is "Dispersed" rather than evaporating...I don't thing dust becomes a vapor, doesn't it just "move off"?

:---[===] *

[Ann]

The "Reindeer Rat-thingy" nebula...

I think a better term is "Dispersed" rather than evaporating...I don't thing dust becomes a vapor, doesn't it just "move off"?

:---[===] *

David Malin once told me (in a private conversation) that dust particles are "cooked" to a smaller size near hot stars. I guess that means that they have evaporated or dispersed.

Or at least shrunk considerably!

Ann

[orin stepanek]

The "Reindeer Rat-thingy" nebula...

I think a better term is "Dispersed" rather than evaporating...I don't thing dust becomes a vapor, doesn't it just "move off"?

:---[===] *

David Malin once told me (in a private conversation) that dust particles are "cooked" to a smaller size near hot stars. I guess that means that they have evaporated or dispersed.

Or at least shrunk considerably!

Ann

Don't know; but, when something evaporates; doesn't the molecules get further apart? Same with dispersing; do particles or whatever separate? similar? Maybe!