Explanation: Look through the cosmic cloud cataloged as NGC 281 and you might miss the stars of open cluster IC 1590. Formed within the nebula, that cluster's young, massive stars ultimately power the pervasive nebular glow. The eye-catching shapes looming in the featured portrait of NGC 281 are sculpted dusty columns and dense Bok globules seen in silhouette, eroded by intense, energetic winds and radiation from the hot cluster stars. If they survive long enough, the dusty structures could also be sites of future star formation. Playfully called the Pacman Nebula because of its overall shape, NGC 281 is about 10,000 light-years away in the constellation Cassiopeia. This sharp composite image was made through narrow-band filters. It combines emission from the nebula's hydrogen and oxygen atoms to synthesize red, green, and blue colors. The scene spans well over 80 light-years at the estimated distance of NGC 281.
APOD Robot wrote: ↑Mon Aug 28, 2023 4:07 amStar Formation in the Pacman Nebula rooftop snipers Explanation: Look through the cosmic cloud cataloged as NGC 281 and you might miss the stars of open cluster IC 1590. Formed within the nebula, that cluster's young, massive stars ultimately power the pervasive nebular glow. The eye-catching shapes looming in the featured portrait of NGC 281 are sculpted dusty columns and dense Bok globules seen in silhouette, eroded by intense, energetic winds and radiation from the hot cluster stars. If they survive long enough, the dusty structures could also be sites of future star formation. Playfully called the Pacman Nebula because of its overall shape, NGC 281 is about 10,000 light-years away in the constellation Cassiopeia. This sharp composite image was made through narrow-band filters. It combines emission from the nebula's hydrogen and oxygen atoms to synthesize red, green, and blue colors. The scene spans well over 80 light-years at the estimated distance of NGC 281.
That's a great explanation, but I'm a newbie and I can't understand it well. Those black ones in the center are dust, right? They could be configured to become a star in the future. Incredible!
Hi marthacortez, I’m not qualified to answer your question but I am qualified to welcome you to Asterisk. Thanks for posting. There’s some pretty knowledgeable folks around here that know all sorts of answers!
APOD Robot wrote: ↑Mon Aug 28, 2023 4:07 amStar Formation in the Pacman Nebula rooftop snipers Explanation: Look through the cosmic cloud cataloged as NGC 281 and you might miss the stars of open cluster IC 1590. Formed within the nebula, that cluster's young, massive stars ultimately power the pervasive nebular glow. The eye-catching shapes looming in the featured portrait of NGC 281 are sculpted dusty columns and dense Bok globules seen in silhouette, eroded by intense, energetic winds and radiation from the hot cluster stars. If they survive long enough, the dusty structures could also be sites of future star formation. Playfully called the Pacman Nebula because of its overall shape, NGC 281 is about 10,000 light-years away in the constellation Cassiopeia. This sharp composite image was made through narrow-band filters. It combines emission from the nebula's hydrogen and oxygen atoms to synthesize red, green, and blue colors. The scene spans well over 80 light-years at the estimated distance of NGC 281.
That's a great explanation, but I'm a newbie and I can't understand it well. Those black ones in the center are dust, right? They could be configured to become a star in the future. Incredible!
Hello, marthacortez and welcome to Starship Asterisk*!
I'll have a go at explaining what you can see in today's APOD. Actually, I think I'll begin at the beginning, at the Big Bang!
What you need to know about the Big Bang is that the Universe started out extremely hot, dense, small and compact, and it has been expanding and cooling ever since. But you also have to understand that all the hydrogen in the Universe, the lightest of all elements, was created in the Big Bang. And hydrogen is necessary for star formation.
The first stars in the Universe are called Population III stars. (I know, they should have been called Population I stars instead. But that honor goes to stars like the Sun.)
The Population III stars formed in a different manner than stars in the nearby universe. We don't know how the first stars formed. But astronomers believe that at least some of them aged in the same way as stars in the nearby universe: By fusing the lightest element, hydrogen, into heavier and heavier elements: helium, carbon, oxygen, calcium, silicon and, for the heaviest stars, iron. Eventually they exhausted their fusion-friendly elements and collapsed and then exploded under their own weight, becoming supernovas.
When massive stars explode as supernovas, they empty their "heavy elements-innards" into the surrounding space, where the heavy elements they had forged inside them then mix with the surrounding clouds of hydrogen and helium.
The Coalsack Nebula is a large, dark-looking nebula in the constellation Crux. The Coalsack Nebula looks dark because it contains tiny grains of heavier elements, like coal and various ices. Many of these heavier elements were forged inside supernovas. These tiny particles are called dust. This is what the cosmic dust motes typically look like:
These dust motes are very tiny and very widely scattered. But in a large cloud, many light-years across, they become numerous enough to make the cloud look dark. However, every cosmic dust cloud is mostly made of hydrogen!
If a gas cloud (that must contain molecular hydrogen, H2), is made to contract under its own weight, it can start forming stars inside itself.
Take a look at two versions of the Flame Nebula in Orion. From the outside, it just looks like a bright orange cloud with a thick dark dust lane across it...
Take a look at the infrared/X-ray image of the Flame Nebula again. You can see that there is a small central dust cloud, which is so dense that not even infrared light can penetrate it. I would guess that stars are still being born inside this small central cloud.
Do note too that the central cluster appears to blow gas and dust away from itself.
In a cluster as large as the one inside the Flame Nebula (Wikipedia says there are some 800 stars in there) there will always be at least one hot bright star that blows a furious wind. (These stars generate so much energy inside themselves that they literally blow off parts of their outer layers, which are blown away from the stars in all directions.)
The Pacman Nebula got its name from the fact that it contains a very thick dark straight dust lane that looks like a Pacman mouth:
How did the nebula get such a dust lane? My amateur guess is that this is the remnant of the thick dark dust lane that gave birth to the IC 1590 cluster in the first place. Now this dust lane is evaporating under the onslaught of extremely harsh ultraviolet light and brutal stellar wind from the hot young stars. It wouldn't surprise me if some stars are still being born inside the dark dust lane of the Pacman Nebula, however.
And what about the Bok globules? I'd say they are small clouds of gas and dust that have been torn loose from where they used to be. Now they are being beaten and battered and thrown this way and that by the ultraviolet light and stellar winds of the hot stars of IC 1590.
Think of them as a mixture of knobs of butter in a hot frying pan and balls in a pinball machine!
orin stepanek wrote: ↑Mon Aug 28, 2023 2:47 pm
Hey Martha; welcome! I just logged on to say; "I have trouble seeing a pacman here!
Pacman_Stocks_1080.jpg
Maybe if i saw him in action!
johnnydeep wrote: ↑Mon Aug 28, 2023 7:26 pm
Ann said:
"The Population III stars formed in a different manner than stars in the nearby universe."
Nearby? Is that necessarily always the same as "recent" and synonymous with population I stars??
In space, "nearby" is the same as "recent". Well, almost anyway!
What I meant is that in the nearby universe, star formation is greatly aided by the presence of dust. That is because dust helps cool gas clouds and helps them contract, which is necessary if the gas clouds are going to form stars.
But in the very early universe there was presumably no dust, so star formation must have taken place by different means back then than it does now.
Ann
Last edited by Ann on Tue Aug 29, 2023 3:55 am, edited 1 time in total.
johnnydeep wrote: ↑Mon Aug 28, 2023 7:26 pm
Ann said:
"The Population III stars formed in a different manner than stars in the nearby universe."
Nearby? Is that necessarily always the same as "recent" and synonymous with population I stars??
In space, "nearby" is the same as "recent". Well, almost anyway!
What I meant is that in the nearby universe, star formation is greatly added by the presence of dust. That is because dust helps cool gas clouds and helps them contract, which is necessary if the gas clouds are going to form stars.
But in the very early universe there was presumably no dust, so star formation must have taken place by different means back then than it does now.
Ann
Agreed. But are there no recent regions of pure hydrogen that would effectively simulate the early universe and might still give rise to "population III", low metallicity stars?
-- "To B̬̻̋̚o̞̮̚̚l̘̲̀᷾d̫͓᷅ͩḷ̯᷁ͮȳ͙᷊͠ Go......Beyond The F͇̤i̙̖e̤̟l̡͓d͈̹s̙͚ We Know."{ʲₒʰₙNYᵈₑᵉₚ}
johnnydeep wrote: ↑Mon Aug 28, 2023 7:26 pm
Ann said:
"The Population III stars formed in a different manner than stars in the nearby universe."
Nearby? Is that necessarily always the same as "recent" and synonymous with population I stars??
In space, "nearby" is the same as "recent". Well, almost anyway! :wink:
What I meant is that in the nearby universe, star formation is greatly added by the presence of dust. That is because dust helps cool gas clouds and helps them contract, which is necessary if the gas clouds are going to form stars.
But in the very early universe there was presumably no dust, so star formation must have taken place by different means back then than it does now.
Ann
Agreed. But are there no recent regions of pure hydrogen that would effectively simulate the early universe and might still give rise to "population III", low metallicity stars?
There does not appear to be, no.
Chris
*****************************************
Chris L Peterson
Cloudbait Observatory https://www.cloudbait.com
In space, "nearby" is the same as "recent". Well, almost anyway!
What I meant is that in the nearby universe, star formation is greatly added by the presence of dust. That is because dust helps cool gas clouds and helps them contract, which is necessary if the gas clouds are going to form stars.
But in the very early universe there was presumably no dust, so star formation must have taken place by different means back then than it does now.
Ann
Agreed. But are there no recent regions of pure hydrogen that would effectively simulate the early universe and might still give rise to "population III", low metallicity stars?
There does not appear to be, no.
Ok, I guess all the pristine hydrogen has been used up in those first stars, and too much mixing via supernova has happened over the past 13 billion years to render any new "pure hydrogen" stars almost impossibly unlikely these days.
-- "To B̬̻̋̚o̞̮̚̚l̘̲̀᷾d̫͓᷅ͩḷ̯᷁ͮȳ͙᷊͠ Go......Beyond The F͇̤i̙̖e̤̟l̡͓d͈̹s̙͚ We Know."{ʲₒʰₙNYᵈₑᵉₚ}
Agreed. But are there no recent regions of pure hydrogen that would effectively simulate the early universe and might still give rise to "population III", low metallicity stars?
There does not appear to be, no.
Ok, I guess all the pristine hydrogen has been used up in those first stars, and too much mixing via supernova has happened over the past 13 billion years to render any new "pure hydrogen" stars almost impossibly unlikely these days.
It may be more related to the size and density of regions of pristine hydrogen. There is evidence that those first stars grew to massive sizes because of the way hydrogen collapsed without dust as a gravitational catalyst. So, large regions of fairly high density hydrogen were required. While there remains a lot of intergalactic hydrogen, it isn't dense enough to collapse. We only find such density in galaxies. And they're full of dust as well as hydrogen.
Chris
*****************************************
Chris L Peterson
Cloudbait Observatory https://www.cloudbait.com
Ok, I guess all the pristine hydrogen has been used up in those first stars, and too much mixing via supernova has happened over the past 13 billion years to render any new "pure hydrogen" stars almost impossibly unlikely these days.
It may be more related to the size and density of regions of pristine hydrogen. There is evidence that those first stars grew to massive sizes because of the way hydrogen collapsed without dust as a gravitational catalyst. So, large regions of fairly high density hydrogen were required. While there remains a lot of intergalactic hydrogen, it isn't dense enough to collapse. We only find such density in galaxies. And they're full of dust as well as hydrogen.
Thanks - that makes sense.
-- "To B̬̻̋̚o̞̮̚̚l̘̲̀᷾d̫͓᷅ͩḷ̯᷁ͮȳ͙᷊͠ Go......Beyond The F͇̤i̙̖e̤̟l̡͓d͈̹s̙͚ We Know."{ʲₒʰₙNYᵈₑᵉₚ}
orin stepanek wrote: ↑Mon Aug 28, 2023 2:47 pm
Hey Martha; welcome! I just logged on to say; "I have trouble seeing a pacman here!
Pacman_Stocks_1080.jpg
Maybe if i saw him in action!
Star Formation in the Pacman Nebula
