Starship Asterisk*

The Dark Tower in Scorpius

Explanation: In silhouette against a crowded star field along the tail of the arachnological constellation Scorpius, this dusty cosmic cloud evokes for some the image of an ominous dark tower. In fact, monstrous clumps of dust and molecular gas collapsing to form stars may well lurk within the dark nebula, a structure that spans almost 40 light-years across this gorgeous telescopic portrait. A cometary globule, the swept-back cloud is shaped by intense ultraviolet radiation from the OB association of very hot stars in NGC 6231, off the upper right corner of the scene. That energetic ultraviolet light also powers the globule's bordering reddish glow of hydrogen gas. Hot stars embedded in the dust can be seen as bluish reflection nebulae. This dark tower and associated nebulae are about 5,000 light-years away.

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Wow, today's APOD is a superb image!


Note all the individual little dusty spurs on the outside of the Dark Tower. Note the embedded stars. And note the glow of red hydrogen alpha following the outline of the Tower, but glowing particularly bright near the top of it.

The Dark Tower is being sculpted (and broken down) by the relentless harsh radiation from the massive open cluster NGC 6231:


As you can see, the orientation of the two "Dark Tower pictures" is not the same. In Gerald Rhemann's image, north is up and east to the left, as is conventional.

Anyway. The Dark Tower is the same kind of object as the Pillars of Creation. Harsh ultraviolet radiation and stellar winds from hot stars are breaking down clouds of gas and dust in the vicinity, leaving the thickest portions of the clouds standing up the longest. The "heads" of the towers or pillars always point directly at the hot stars sculpting them.


A big difference between the Dark Tower region and the Pillars of Creation region appears to be that a lot of the gas and dust of the Eagle nebula remains, whereas most of the nebulosity around NGC 6231 has been blown away and scattered. Only the Dark Tower remains standing (or lying down, whatever you fancy).


Ann

I used up my three attachments in my previous post, so I'll have to make another post to show you more of the vicinity of the Dark Tower.


The red nebula IC 4628, the nameless red nebula near bottom left of the image, and the Dark Tower in Scorpius, are all clearly remnants of the original nebula that gave birth to the massive open cluster, NGC 6231.

In the picture below you can see even more of the vicinity of NGC 6231. Note the red nebulosity around the Dark Tower too, another remnant of the nebula that gave birth to NGC 6231. And what's that thing in the middle of the picture? Read on to find out...



NGC 6231, IC 4628 and the line of stars that seems to connect them, along with the three bright stars near bottom of the picture, are collectively known as the False Comet.

Ann

Ann wrote: ↑Thu Aug 22, 2024 5:45 am Wow, today's APOD is a superb image!

DarkTowerCDK700-Selby1024[1].jpg

The Dark Tower in Scorpius
Image Credit & Copyright: Mike Selby

Note all the individual little dusty spurs on the outside of the Dark Tower. Note the embedded stars. And note the glow of red hydrogen alpha following the outline of the Tower, but glowing particularly bright near the top of it.

The Dark Tower is being sculpted (and broken down) by the relentless harsh radiation from the massive open cluster NGC 6231:

Click to view full size image

Dark Tower in Scorpius and NGC 6231 by Gerald Rhemann.png

The Dark Tower in Scorpius being sculpted by open cluster NGC 6231.
Credit: Gerald Rhemann.

...
Ann

How far away is NGC 6231? Based on that image with both in the FOV, it's got to be several tens of lightyears, right? Is that really near enough to the "dark tower" to be able to do all that sculpting?

EDIT: apparently, and surprisingly - to me! - even at the estimated 100 ly distance, it CAN! From http://annesastronomynews.com/photo-gal ... n-goldman/

The Dark Tower is an elongated dark cloud of dust and gas of about 40 light-years across, located some 5,000 light-years away from Earth in the southern constellation of Scorpius.

Silhouetted against a crowded star field, the Dark Tower is known as a cometary globule – an isolated, relatively small cloud of gas and dust within the Milky Way – which is extending from the lower right to the top of the tower, left and above center of the image. Probably, clumps of dust and molecular gas are collapsing to form stars within this dark nebula.

Its swept-back shape is sculpted by the intense ultraviolet radiation from very hot stars in NGC 6231, which lies about 100 light-years away from the Dark Tower (off the upper edge of the image). The direction of the radiation source can be seen from the flow pattern in the dark cloud.