by Ann » Mon Aug 28, 2023 3:49 pm
marthacortez wrote: ↑Mon Aug 28, 2023 9:00 am
APOD Robot wrote: ↑Mon Aug 28, 2023 4:07 am
Star 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, H
2), 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...
...but if we peer inside, with the help of infrared light and X-rays, we can see a cluster of newborn stars inside.
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.)
Now let's look at today's APOD:
The central cluster is so compact that it is hard to see it. Let's look at a closeup of the cluster, IC 1590:
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!
[youtube]
https://www.youtube.com/shorts/YeG-elhf ... ture=share[/youtube]
Click to play embedded YouTube video.
You have to click on the link to the first Youtube video to make it work. Sorry!
Ann
[quote=marthacortez post_id=333300 time=1693213249 user_id=147291]
[quote="APOD Robot" post_id=333297 time=1693195638 user_id=128559]
[url=https://apod.nasa.gov/apod/ap230828.html] [img]https://apod.nasa.gov/apod/calendar/S_230828.jpg[/img] [size=150]Star Formation in the Pacman Nebula[/size][/url]
[url=https://rooftopsnipers.io][size=1]rooftop snipers[/size][/url]
[b] Explanation: [/b] Look through the cosmic cloud cataloged as NGC 281 and you might miss the stars of open cluster [url=https://ui.adsabs.harvard.edu/abs/1997AJ....113.2116G/abstract]IC 1590[/url]. Formed [url=https://chandra.harvard.edu/photo/2007/ngc281/]within the nebula[/url], 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 [url=https://en.wikipedia.org/wiki/Bok_globule]Bok globules[/url] seen in silhouette, eroded by intense, energetic winds and [url=https://science.nasa.gov/ems/10_ultravioletwaves]radiation[/url] from the hot cluster stars. If they survive long enough, the dusty structures could also be sites of future star formation. [url=http://www.google.com/pacman/]Playfully called[/url] the Pacman Nebula because of its overall shape, NGC 281 is about 10,000 light-years away in the constellation [url=http://www.hawastsoc.org/deepsky/cas/]Cassiopeia[/url]. This sharp composite image was made through [url=https://apod.nasa.gov/apod/ap071102.html]narrow-band[/url] filters. It combines emission from the nebula's hydrogen and oxygen atoms to [url=https://hubblesite.org/contents/articles/the-meaning-of-light-and-color]synthesize[/url] red, green, and blue colors. The scene spans well over 80 [url=https://spaceplace.nasa.gov/light-year/en/]light-years[/url] at the estimated distance of [url=https://en.wikipedia.org/wiki/NGC_281]NGC 281[/url].
[table][tr][td=left][url=https://asterisk.apod.com/discuss_apod.php?date=230827][b]<< Previous APOD[/b][/url][/td] [td=center][url=https://asterisk.apod.com/view_retro.php?date=0828][b]This Day in APOD[/b][/url][/td] [td=right][url=https://asterisk.apod.com/discuss_apod.php?date=230829][b]Next APOD >>[/b][/url][/td][/tr][/table]
[/quote]
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!
[/quote]
Hello, marthacortez and welcome to Starship Asterisk*! :D
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!
[img3="The Big Bang and the evolution of the Universe. Illustration: NASA/WMAP Science Team/ Modified by Cherkash"]https://upload.wikimedia.org/wikipedia/commons/thumb/6/6f/CMB_Timeline300_no_WMAP.jpg/1280px-CMB_Timeline300_no_WMAP.jpg[/img3]
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.)
[img3="Artist's impression of the first stars, 400 million years after the Big Bang. Illustration: NASA/WMAP Science Team"]https://upload.wikimedia.org/wikipedia/commons/thumb/9/98/NASA-WMAP-first-stars.jpg/1920px-NASA-WMAP-first-stars.jpg[/img3]
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.
[img3="A supernova. Illustration: NASA/CXC/M.Weiss"]https://spaceplace.nasa.gov/supernova/en/supernova1.en.jpg[/img3]
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.
[img3="The Coalsack Nebula. Image credit: ESO/S. Brunier"]https://upload.wikimedia.org/wikipedia/commons/thumb/7/7c/Coalsack-ESO-B06.jpg/1028px-Coalsack-ESO-B06.jpg?20091121165846[/img3]
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:
[img3=""]https://encrypted-tbn0.gstatic.com/images?q=tbn:ANd9GcReQXyLqWXxmnHR_cd6DlXYVCewjowIqglwFg&usqp=CAU[/img3]
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, H[sub][size=85]2[/size][/sub]), 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...
[img3="The Flame Nebula in visible light. Credit: Ljubinko Jovanovic"]https://upload.wikimedia.org/wikipedia/commons/thumb/5/50/The_Flame_Nebula.jpg/1280px-The_Flame_Nebula.jpg[/img3]
...but if we peer inside, with the help of infrared light and X-rays, we can see a cluster of newborn stars inside.
[img3="The Flame Nebula in infrared light and X-rays. Credit: X-ray: NASA/CXC/PSU/K.Getman, E.Feigelson, M.Kuhn & the MYStIX team; Infrared: NASA/JPL-Caltech"]https://upload.wikimedia.org/wikipedia/commons/thumb/3/36/NASA-FlameNebula-NGC2024-20140507.jpg/1024px-NASA-FlameNebula-NGC2024-20140507.jpg[/img3]
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.
[attachment=0]Flame Nebula infrared X rays stellar wind.png[/attachment]
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.)
Now let's look at today's APOD:
[img3="Star Formation in the Pacman Nebula.
Image Credit & Copyright: Craig Stocks"]https://apod.nasa.gov/apod/image/2308/Pacman_Stocks_1080.jpg[/img3]
The central cluster is so compact that it is hard to see it. Let's look at a closeup of the cluster, IC 1590:
[img3="Infrared and X-ray picture of IC 1590, the central cluster of the Pacman Nebula. The cluster contains some extremely hot and powerful stars which emit copious amounts of ultraviolet light and blow a terrific wind. In the picture, you can see the 'main cluster' surrounded by 10 million degree gas (in purple). Another, younger cluster is emerging from the gray cloud at lower right. Credit: X-ray: NASA/CXC/CfA/S.Wolk; IR: NASA/JPL/CfA/S.Wolk"]https://upload.wikimedia.org/wikipedia/commons/thumb/a/a6/The_Pacman_Nebula.jpg/1024px-The_Pacman_Nebula.jpg[/img3]
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:
[img3=""]https://i.pinimg.com/originals/a8/5c/8e/a85c8e69d289d9e8de9f5813e5bbc06b.jpg[/img3]
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!
[youtube]https://www.youtube.com/shorts/YeG-elhfNIc?feature=share[/youtube]
[youtube]https://www.youtube.com/watch?v=aCOhLd9uXBs[/youtube]
You have to click on the link to the first Youtube video to make it work. Sorry!
Ann