APOD: CG4: The Globule and the Galaxy (2024 May 21)

[APOD Robot]

CG4: The Globule and the Galaxy

Explanation: Can a gas cloud eat a galaxy? It's not even close. The "claw" of this odd looking "creature" in the featured photo is a gas cloud known as a cometary globule. This globule, however, has ruptured. Cometary globules are typically characterized by dusty heads and elongated tails. These features cause cometary globules to have visual similarities to comets, but in reality they are very much different. Globules are frequently the birthplaces of stars, and many show very young stars in their heads. The reason for the rupture in the head of this object is not yet known. The galaxy to the left of the globule is huge, very far in the distance, and only placed near CG4 by chance superposition.

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[Ann]

I always want to put things in perspective.

CG4: The Globule and the Galaxy. Image Credit: CTIO, NOIRLab, DOE, NSF, AURA; Processing: T. A. Rector (U. Alaska Anchorage/NSF’s NOIRLab), D. de Martin & M. Zamani (NSF’s NOIRLab)

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Why is that globule cometary? What made it open its mouth? Nearby hot bright stars, sure. What stars?

I found the coordinates for CG4, which is the name of this thing, and saw that it is located relatively close to Gamma Velorum, an enormous powerhouse in constellation Vela, the Sail. So I googled CG4 + Gamma Velorum and found... nothing.

This is the best I can do to show you where CG4 is in relation to Gamma Velorum:

Gamma Velorum (bright star at lower right) and the Vela supernova remnant. Credit: Robert Gendler, Roberto Colombari, Digitized Sky Survey (POSS II)

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This way to CG4.

To show you why it is important to put cometary globules into perspective, consider another such globule, the Dark Tower in Scorpius:

The Dark Tower in Scorpius and star cluster NGC 6231.
Credit: Gerald Rehmann.

So, yeah. Perspective is important. Gerald Rehmann showed us why the Dark Tower in Scorpius and the massive open cluster NGC 6231 belong together. Now we really need a picture that shows us Gamma Velorum and CG4 in the same frame.

Oh, and... why has CG4 ruptured? How about Gamma Velorum released a jet of energy some time in the past, and CG4 took a direct hit? Perhaps the Wolf-Rayet component of Gamma Velorum had an outburst? It's a mean thing, Gamma Velorum.

And that galaxy that CG4 appears to be eating? Oh, it's PGC 21338, also known as ESO 257-19. It may have an active galactic nucleus, said Simbad. What's the distance to that thing? I don't know!

Ann

[mister T]

Very Cool image!

I am reminded of the "doomsday machine" from the original Star Trek series.

[Uncle__Jeff]

Yup, it's the Doomsday Machine in my mind also. Let's make the name stick
https://trekmovie.com/wp-content/upload ... msday2.jpg

[AVAO]

I always want to put things in perspective.

CG4: The Globule and the Galaxy. Image Credit: CTIO, NOIRLab, DOE, NSF, AURA; Processing: T. A. Rector (U. Alaska Anchorage/NSF’s NOIRLab), D. de Martin & M. Zamani (NSF’s NOIRLab)

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Why is that globule cometary? What made it open its mouth? Nearby hot bright stars, sure. What stars?

I found the coordinates for CG4, which is the name of this thing, and saw that it is located relatively close to Gamma Velorum, an enormous powerhouse in constellation Vela, the Sail. So I googled CG4 + Gamma Velorum and found... nothing.

This is the best I can do to show you where CG4 is in relation to Gamma Velorum:

Gamma Velorum (bright star at lower right) and the Vela supernova remnant. Credit: Robert Gendler, Roberto Colombari, Digitized Sky Survey (POSS II)

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Gama Velorum and this way to CG4 Gendler Columbari.png

This way to CG4.

To show you why it is important to put cometary globules into perspective, consider another such globule, the Dark Tower in Scorpius:

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

The Dark Tower in Scorpius and star cluster NGC 6231.
Credit: Gerald Rehmann.

So, yeah. Perspective is important. Gerald Rehmann showed us why the Dark Tower in Scorpius and the massive open cluster NGC 6231 belong together. Now we really need a picture that shows us Gamma Velorum and CG4 in the same frame.

Oh, and... why has CG4 ruptured? How about Gamma Velorum released a jet of energy some time in the past, and CG4 took a direct hit? Perhaps the Wolf-Rayet component of Gamma Velorum had an outburst? It's a mean thing, Gamma Velorum.

And that galaxy that CG4 appears to be eating? Oh, it's PGC 21338, also known as ESO 257-19. It may have an active galactic nucleus, said Simbad. What's the distance to that thing? I don't know!

Ann

ThanX Ann

Your hypothesis regarding gamma velorum is bold, but I also think correct.

Regarding the two YSOs, I find MASS_J073439.9-465548 (1) particularly noteworthy.
This seems to be in an intermediate stage and is almost floating freely in space.
According to the classical view, stripped of its dusty birth shell.

Click to view full size image

https://www.watson.ch/wissen/astronomie ... nkugel-cg4

[Ann]

Cometary globules are, in principle, the same kind of objects as the Pillars of Creation, and even pretty much the same objects as the little "pillars" along the rim of planetary nebulas. They are "what remains standing" after hot stars have blown away thinner material around them. The pillars are typically most massive in their "heads", and the "heads" shield the area immediately below them, creating the elongated structures.

The Pillars of Creation (below center, and also at upper left) in the Eagle Nebula. Hot bright stars in cluster NGC 6611 are sculpting the pillars. Credit: ESA.

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These cometary knots are found along the inner rim of the Helix Nebula. They all point at the central blisteringly hot white dwarf. Credit: C. Robert O'Dell and Kerry P. Handron (Rice University), NASA

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Ann

[Ann]

ThanX Ann

Your hypothesis regarding gamma velorum is bold, but I also think correct.

Regarding the two YSOs, I find MASS_J073439.9-465548 (1) particularly noteworthy.
This seems to be in an intermediate stage and is almost floating freely in space.
According to the classical view, stripped of its dusty birth shell.

Click to view full size image

https://www.watson.ch/wissen/astronomie ... nkugel-cg4

Thanks, Jac!

However, NOIRLab doesn't agree with me about Gamma Velorum:

NOIRLab wrote:

While astronomers have observed these structures throughout the Milky Way, the overwhelming majority of them, including CG 4, are found within a huge patch of glowing gas called the Gum Nebula. Believed to be the expanding remains of a supernova that took place about a million years ago, the Gum Nebula is currently known to contain at least 31 cometary globules in addition to CG 4.

....

The second idea is that cometary globules are shaped by a combination of stellar winds and radiation pressure from nearby hot, massive stars. In fact, all of the cometary globules found within the Gum Nebula appear to have tails pointing away from the center of the nebula, which is where the Vela Supernova Remnant and Vela Pulsar are located. The Vela Pulsar is a rapidly spinning neutron star that was formed when a massive star collapsed, and it’s possible that its stellar winds and radiation pressure are shaping the nearby globules.

The smiley face of the Vela pulsar may be the source that has sculpted the cometary globules in the vicinity of the Vela supernova remnant. Credit: X-RAY: (IXPE) FEI XIE, MSFC/NASA & (CHANDRA) SAO/CXC/NASA; OPTICAL: CHANDRA, STSCI HUBBLE/NASA, PROCESSING BY JUDY SCHMIDT; HUBBLE/CHANDRA/IXPE PROCESSING & COMPOSITING BY KIMBERLY ARCAND & NANCY WOLK, SAO/CXC/NASA

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Ann