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APOD: Stars, Dust and Nebula in NGC 6559 (2023 Jul 10)
Posted: Mon Jul 10, 2023 4:05 am
by APOD Robot
Stars, Dust and Nebula in NGC 6559
Explanation: When stars form, pandemonium reigns. A
textbook case is the star forming region
NGC 6559. Visible in the
featured image are red glowing
emission nebulas of
hydrogen, blue
reflection nebulas of
dust, dark
absorption nebulas of dust, and the stars that formed from them. The
first massive stars formed from the dense gas will emit
energetic light and
winds that erode, fragment, and
sculpt their birthplace. And then they
explode. The resulting
morass can be as beautiful as it is
complex. After tens of millions of years, the dust
boils away, the gas gets swept away, and all that is left is a bare
open cluster of stars.
Re: APOD: Stars, Dust and Nebula in NGC 6559 (2023 Jul 10)
Posted: Mon Jul 10, 2023 5:33 am
by Ann
Stars, Dust and Nebula in NGC 6559
Image Credit & Copyright: Adam Block, Telescope Live
Likely mechanism for creating the red ridge of NGC 6559
NGC 6559 is a young region of star formation. It is full of gas and dust. A long winding dust lane seems to connect the hot O-type star 11 Sagittarii (HD 165921) with the blue reflection nebula illuminated by newborn B-type stars. The reason why the the reflection nebula is blue is because the B-type stars are not hot enough to ionize a red emission nebula. The likely reason why the red ridge is so very red is that it is being "pushed from two directions" and ionized by clashing stellar winds. Of course the ultraviolet light from 11 Sgr also contributes strongly to the ionization of ridge.
There are some similarities between the NGC 6559 region (the subject of today's APOD) and the star forming region of Perseus and Taurus:
The California Nebula is being both "pushed" and ionized by O-type star Xi Per.
Perhaps the mechanism for creating the red ridge of NGC 6559 is slightly similar.
Ann
Re: APOD: Stars, Dust and Nebula in NGC 6559 (2023 Jul 10)
Posted: Mon Jul 10, 2023 2:19 pm
by johnnydeep
Just wanted to give a hearty shoutout to the OpenStax Astronomy textbook that anyone can either read for free online or download the full 1133 page PDF and read offline with an e-reader. One big benefit of all the textbooks available at OpenStax is that they are constantly being updated to reflect new information, such as the JWST images from the
link about star formation provided in the APOD text.
Good stuff! - see
https://openstax.org/details/books/astronomy-2e
Re: APOD: Stars, Dust and Nebula in NGC 6559 (2023 Jul 10)
Posted: Mon Jul 10, 2023 3:57 pm
by zendae
"...the dust boils away, the gas gets swept away..."
There are a lot of tiny motes out there getting swept and blown hither and thither. I wonder if there is a 'particle to 3D area' ratio that determines when there is and when there is not a vacuum. Or is a vacuum such an absolute that it doesn't actually exist. Between visible and dark matter, is space a vacuum anywhere? Is it only a quantum size state. Is any space that has no particle in it a tiny vacuum.
Re: APOD: Stars, Dust and Nebula in NGC 6559 (2023 Jul 10)
Posted: Mon Jul 10, 2023 4:10 pm
by Chris Peterson
zendae wrote: ↑Mon Jul 10, 2023 3:57 pm
"...the dust boils away, the gas gets swept away..."
There are a lot of tiny motes out there getting swept and blown hither and thither. I wonder if there is a 'particle to 3D area' ratio that determines when there is and when there is not a vacuum. Or is a vacuum such an absolute that it doesn't actually exist. Between visible and dark matter, is space a vacuum anywhere? Is it only a quantum size state. Is any space that has no particle in it a tiny vacuum.
Most of the volume of space is free of any particles (other than virtual ones). A true vacuum. But the density of particles is high enough that in most of the Universe the volume of particle free areas is small- cubic millimeters or less.
Re: APOD: Stars, Dust and Nebula in NGC 6559 (2023 Jul 10)
Posted: Mon Jul 10, 2023 7:04 pm
by zendae
Chris Peterson wrote: ↑Mon Jul 10, 2023 4:10 pm
Most of the volume of space is free of any particles (other than virtual ones). A true vacuum. But the density of particles is high enough that in most of the Universe the volume of particle free areas is small- cubic millimeters or less.
Re: APOD: Stars, Dust and Nebula in NGC 6559 (2023 Jul 10)
Posted: Mon Jul 10, 2023 7:04 pm
by zendae
Thanks. That makes a lot of sense.
Re: APOD: Stars, Dust and Nebula in NGC 6559 (2023 Jul 10)
Posted: Mon Jul 10, 2023 7:49 pm
by orin stepanek
The dark nebula looks somewhat like a snake
Naughty doggy!
![Laughing :lol2:](./images/smilies/asterisk_laugh.gif)
Re: APOD: Stars, Dust and Nebula in NGC 6559 (2023 Jul 10)
Posted: Tue Jul 11, 2023 5:39 am
by VictorBorun
Ann wrote: ↑Mon Jul 10, 2023 5:33 am
![Image](https://asterisk.apod.com/download/file.php?id=47854&t=1)
Likely mechanism for creating the red ridge of NGC 6559
This ridge— judging by visible brightness of the likely stellar wind sources — should drift in 2 o'clock direction.
I wonder if we know some H-alpha triple peaks somewhere
![Image](https://images.squarespace-cdn.com/content/v1/5486978ce4b0997b9acf758a/1452642589397-XYBLXL3XTLBXT30FRC19/image-asset.png)