APOD: CG4: A Ruptured Cometary Globule (2021 Jul 26)

[APOD Robot]

CG4: A Ruptured Cometary Globule

Explanation: Can a gas cloud grab 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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[VictorBorun]

where is the source of the harsh stellar wind that made this ruptured cometary globe?
Has it gone supernova already?

[Ann]

where is the source of the harsh stellar wind that made this ruptured cometary globe?
Has it gone supernova already?

If you ask me, a cometary globule is a site of low-mass star formation. The stars that are born there are not going to go supernova, unless a pair of them evolve so that one or both of them turn into a white dwarf (and that is going to take a long time), and the most massive white dwarf receives so much extra mass from its companion that it exceeds its Chandrasekhar limit and goes supernova type Ia.

But as I said, that is going to take a long time.

Dust pillar with jets in the Carina Nebula. Image Credit: NASA, ESA, N. Smith (U. California, Berkeley) et al., and The Hubble Heritage Team (STScI/AURA).

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Blue nebula Ou4, inside large red nebula Sh2-129, the Squid Nebula. Ou4 is the product of some kind of stellar outburst, centered on massive triple star HR 8119. Image Credit & Copyright: Yannick Akar.

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So why has the head of cometary globule CG4 ruptured? The simplest explanation that I can think of is that there has been a (stellar) outburst of some sort in or very near the head of the cometary globule. An interesting possibility is that a star has formed at the top of the globule, creating so much sound and fury that it ripped the head of the globule open. The problem with that scenario is that we see no sign of the kind of star in or near CG4 that could have created such a massive outburst.

(Besides, the typical jets emitted by baby stars in the process of forming appear to be emitted perpendicular to the elongated dust structures that they are born from. The jets don't seem to be emitted "along" the length of the dust pillar, in such a way that the head of the pillar might be split open by a jet.)

eso1503c[1].jpg

Wide field image of CG4. No star in the vicinity appears able
to rip the head of the globule open. Credit: ESO and Digitized Sky Survey 2

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Another possibility is that the force that made the rupture came from outside. But the problem with that scenario is that can see no star in the vicinity that appears "angry" enough to have produced such a massive outburst. Note, too, that none of the seemingly nearby stars is positioned right "above" the ruptured head of CG4.

Anyway, cometary globule CG4 gives a new meaning to the expression "My head is splitting"!

Ann

P.S. By the way, the galaxy that CG4 appears to be trying to engulf is ESO 257-19 (PGC 21338), which according to Anne's Astronomy is more than a hundred million light-years away.

P.P.S. I found a lovely wide field image of CG4 and the entire dust complex that it belongs to. Go to this page to see it.

[Randall Rathbun]

https://www.jpl.nasa.gov/images/cosmic- ... gh-the-sky states that ESO-257-19 is 118 million light years away, but I had to use SIMBAD to actually identify this galaxy, the 2 arcmin search box was too small, it had to be made 10 arcmin to pick up the galaxy from CG4.

[rstevenson]

I am curious why so much of the text of today’s APOD comes from this page…
http://annesastronomynews.com/annes-pic ... obule-cg4/

Attribution is a good thing, even if the originator volunteers the text for APOD’s use.

Rob

[orin stepanek]

CG4_Rolland_4000.jpg

Cometary Globule gone bad!

imagem_ht_07-04-23.jpg

Kitty; What are you doing?

[De58te]

Curious about some information left out. What is this huge galaxy's name? The Wikipedia link says that the size of CG 4 is 8 ly long and it is about 1,300 ly away from Earth. Given that, can we figure out how far away the galaxy is assuming it is the same size of the Milky Way?

[neufer]

Curious about some information left out. What is this huge galaxy's name? The Wikipedia link says that the size of CG 4 is 8 ly long and it is about 1,300 ly away from Earth. Given that, can we figure out how far away the galaxy is assuming it is the same size of the Milky Way?

• http://simbad.u-strasbg.fr/simbad/sim-i ... ESO+257-19

[neufer]

Click to play embedded YouTube video.

I found a lovely wide field image of CG4 and the entire dust complex that it belongs to. Go to this page to see it.

[neufer]

where is the source of the harsh stellar wind that made this ruptured cometary globe?

Has it gone supernova already?

---

<<CG 4, commonly referred to as God's Hand, is a star-forming region located in the Puppis constellation, about 1,300 light-years (400 pc) from Earth. CG 4, and the nearby cometary globules, generally point away from the Vela Supernova Remnant, located at the center of the Gum Nebula. The Vela supernova remnant is a supernova remnant in the southern constellation Vela. Its source Type II supernova exploded approximately 11,000–12,300 years ago (and was about 800 light-years away). The association of the Vela supernova remnant with the Vela pulsar, made by astronomers at the University of Sydney in 1968, was direct observational evidence that supernovae form neutron stars.

Code: Select all

		Vela pulsar	   CG 4
----------------------------------------------------------
Right ascension	08h 35m 21s	07h 34m 09s	

Declination	−45° 10′ 35″	−46° 54′ 18″	

In 1976, photographs from the UK Schmidt Telescope—operated by the Australian Astronomical Observatory—showed several objects resembling comets, located in the Gum Nebula, an emission nebula of the constellation. Due to their particular shape, these objects came to be known as cometary globules. Each globule has a dense, dark, ruptured head and a very long tail, with the latter pointing away from the Vela Supernova Remnant. As a part of the ESO Cosmic Gems program, the European Southern Observatory released an image of CG 4 in January 2015 showing the head of the nebula.>>

[neufer]

Kitty; What are you doing?

Look, Vela. I find this kitten picture of yours without any Puppis.

[Q Who (not that one)]

Is it just me or does CG4 look like the planet-munching doomsday machine from the original Star Trek episode of the same name?

[neufer]

Is it just me or does CG4 look like the planet-munching doomsday machine from the original Star Trek episode of the same name?

Click to play embedded YouTube video.

<<The USS Enterprise, following a trail of mysteriously destroyed star systems, picks up the automated distress beacon of one of Enterprise's sister ships, the USS Constellation. Upon arrival, the Constellation is found heavily damaged and drifting in space; Captain Kirk, Chief Medical Officer Dr. McCoy, Chief Engineer Scott, and a damage control team transport to the ship to evaluate her. There they discover the ship's commander Commodore Matt Decker, who is suffering from severe mental shock. Decker explains that he and his crew had discovered a giant machine, miles long, that used beams of antiprotons to tear planets apart, consuming the rubble for fuel. The attack by Constellation on the machine was ineffective and the ship suffered heavy damage. Decker evacuated his crew to one of the planets of the system, which the machine subsequently destroyed. Kirk theorizes that the machine is an ancient doomsday machine, which must be stopped before it reaches more populated sectors of the galaxy. McCoy and Decker transport to Enterprise, which has taken Constellation in tow. Kirk attends to Constellation's nonfunctional view-screen. With the rest of the boarding party transported back to Enterprise, Kirk aims Constellation at the maw of the planet killer, triggers the timer, and orders Enterprise to beam him aboard. The transporter malfunctions, and Scott races to set it right. With virtually no time to spare, Kirk is safely beamed aboard Enterprise as Constellation explodes inside the planet killer, leaving it dead in space, its threat ended. >>

Gastrotrichs (a.k.a., hairybellies or hairybacks)

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<<The gastrotrichs, commonly referred to as hairybellies or hairybacks, are a group of microscopic (0.06-3.0 mm), worm-like, pseudocoelomate animals, and are widely distributed and abundant in freshwater and marine environments. They are bilaterally symmetrical, with a transparent strap-shaped or bowling pin-shaped body, arched dorsally and flattened ventrally. The anterior end is not clearly defined as a head but contains the sense organs, brain and pharynx. Cilia are found around the mouth and on the ventral (belly/back) surface of the head & body. The trunk contains the gut and the reproductive organs. At the posterior end of the body are two projections with cement glands that serve in adhesion. This is a double-gland system where one gland secretes the glue and another secretes a de-adhesive agent to sever the connection.

Gastrotrichs feed on detritus, sucking up organic particles with their muscular pharynx. They are hermaphrodites, the marine species producing eggs which develop directly into miniature adults. The freshwater species are parthenogenetic, producing unfertilised eggs, and at least one species is viviparous. Gastrotrichs mature with great rapidity and have lifespans of only a few days.>>

[kerberos]

I want to know what that interesting ring of stars is, at the galaxy's lower left...gravitational lensing?

[Chris Peterson]

I want to know what that interesting ring of stars is, at the galaxy's lower left...gravitational lensing?

It is a chance alignment of stars that your brain desperately wants to see a pattern in.

[kerberos]

I want to know what that interesting ring of stars is, at the galaxy's lower left...gravitational lensing?

It is a chance alignment of stars that your brain desperately wants to see a pattern in.

...the pattern is there, not imagined...my question was...is the pattern something interesting, or a random alignment of stars.

[Chris Peterson]

I want to know what that interesting ring of stars is, at the galaxy's lower left...gravitational lensing?

It is a chance alignment of stars that your brain desperately wants to see a pattern in.

...the pattern is there, not imagined...my question was...is the pattern something interesting, or a random alignment of stars.

I did not say the pattern was imagined, only that our brains are pattern detectors. These stars are unrelated. The pattern has no physical significance.

[VictorBorun]

After all CG4 cometary is stretched away from a fresh SN neutron star remnant, Vela Pulsar which is just 12 kiloyears old.
Here I overlayed X ray of Vela Pulsar and the narrow spectral lines pic from this APOD on Sindbad's optical sky:

CG4+Vela Pulsar+.png

[VictorBorun]

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<<CG 4, commonly referred to as God's Hand, is a star-forming region located in the Puppis constellation, about 1,300 light-years (400 pc) from Earth. CG 4, and the nearby cometary globules, generally point away from the Vela Supernova Remnant, located at the center of the Gum Nebula. The Vela supernova remnant is a supernova remnant in the southern constellation Vela. Its source Type II supernova exploded approximately 11,000–12,300 years ago (and was about 800 light-years away). The association of the Vela supernova remnant with the Vela pulsar, made by astronomers at the University of Sydney in 1968, was direct observational evidence that supernovae form neutron stars.

Code: Select all

		Vela pulsar	   CG 4
----------------------------------------------------------
Right ascension	08h 35m 21s	07h 34m 09s	

Declination	−45° 10′ 35″	−46° 54′ 18″	

In 1976, photographs from the UK Schmidt Telescope—operated by the Australian Astronomical Observatory—showed several objects resembling comets, located in the Gum Nebula, an emission nebula of the constellation. Due to their particular shape, these objects came to be known as cometary globules. Each globule has a dense, dark, ruptured head and a very long tail, with the latter pointing away from the Vela Supernova Remnant. As a part of the ESO Cosmic Gems program, the European Southern Observatory released an image of CG 4 in January 2015 showing the head of the nebula.>>

I took it as a challenge to compile an image that proves the phrase "generally point away from the Vela Supernova Remnant"