cometary globules

Dark Tower - A Bridge to Nowhere - Near Open Cluster NGC 6231
The Dark Tower in the constellation of Scorpius is an elongated dark cloud of dust and gas embedded in a rich sea of stars. It is known as a cometary globule where intense UV radiation from very hot OB-type stars in NGC6231 (off the top edge of the image) sculpts the resulting columnar structure of the Dark Tower. The UV radiation is sufficiently strong to ionize hydrogen, producing an ominous pink glow around the top of the Dark Tower and similarly to ionize the background medium, such as the interesting “bridge to nowhere” of H-alpha light extending from the tip of the Dark Tower toward the left side of the image. There are several blue reflection nebula embedded within the Dark Tower. These structures are stellar nurseries. The Dark Tower is 40 light years across and 5,000 light years distant.

Credit: Don Goldman

Globule Goes Chomp

The flower-like image of this star-forming region in Earth’s southern skies was imaged using a 64-megapixel Mosaic imaging camera on the National Science Foundation’s Victor M. Blanco telescope at Cerro Tololo Inter-American Observatory.

Cometary globules are isolated, relatively small clouds of gas and dust within the Milky Way. This example, called CG4, is about 1,300 light years from Earth. Its head is some 1.5 light-years in diameter, and its tail is about eight light-years long. The dusty cloud contains enough material to make several Sun-sized stars. CG4 is located in the constellation of Puppis.

The head of the nebula is opaque, but glows because it is illuminated by light from nearby hot stars. Their energy is gradually destroying the dusty head of the globule, sweeping away the tiny particles which scatter the starlight. This particular globule shows a faint red glow from electrically charged hydrogen, and it seems about to devour an edge-on spiral galaxy (ESO 257-19) in the upper left. In reality, this galaxy is more than a hundred million light-years further away, far beyond CG4. The image from the Blanco 4-meter telescope was taken in four filters, three of which are for blue, green and near-infrared light. The fourth is designed to isolate a specific color of red, known as hydrogen-alpha, which is produced by warm hydrogen gas.

Image Credit: T.A. Rector/University of Alaska Anchorage, T. Abbott and NOAO/AURA/NSF

Located roughly 1300 light years distant in the constellation Pupis at the southern end of the great Gum Nebula; these objects are what are known as cometary globule complex CG30, CG31 & CG38.

Created by gravity; these pockets of dense interstellar gas and dust stretch roughly one light year and are molded into their comet-like shapes through ionization by nearby stars that shower them with energetic ultraviolet (UV) radiation.

In the dense heads of these universal sculptures lie infant stars that are still undergoing formation. Over time gravity will continue to pool material into the densest regions. It will then contract, collapse and heat the local region.

This process will repeat over and over until it reaches the critical point where the conditions allow for fusion to take place and the star will come to life.

In the annotated image presented below.  The head of CG30 contains the bright Herbig-Haro object HH120 that is powered by a young star, CG 30-IRS4 based upon IR data.   Distance estimates are 700-1300 light years.  The image is ~42’ x 42’ and North is down.

CG30,31 is a cometary globule complex located in southern portion of the large Gum Nebula at RA 8hr 08min 50.5s and DEC -35d 50m 54s near the constellations of Vela and Pupis.

Overall, we think the Gum Nebula is pretty cool! Well actually it is fascinating in our books…

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An Unusual Globule in IC 1396 Energetic light from a bright young star is eating away the dust of the dark cometary globule near the top of the image. Jets and winds of particles emitted from this star are also pushing away ambient gas and dust

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A ruptured cometary globule CG4 (and some cool galaxies)

Cometary globules are clouds of gas and dust formed by the interplay of cold molecular clouds and hot stars. They are typically characterized by dusty heads and elongated tails, what make them look like comets, although they are actually very different.

Image by Jason Jennings

This is IC 1396 or as it’s more commonly known, the Elephant’s Trunk Nebula. Energetic light from this star is eating away the dust of the dark cometary globule near the top of the above image. Jets and winds of particles emitted from this star are also pushing away ambient gas and dust. Nearly 3,000 light-years distant, the relatively faint IC 1396 complex covers a much larger region on the sky than shown here, with an apparent width of more than 10 full moons.

Credit: T. Rector (U. Alaska Anchorage) & H. Schweiker (WIYN, NOAO, AURA, NSF)

CG4: A Ruptured Cometary Globule

Image Credit & Copyright: Jason Jennings (cosmicphotos)

Explanation: Can a gas cloud grab a galaxy? It’s not even close. The “claw” of this odd looking “creature” in the above 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 completely known. The galaxy to the left of the globule is huge, very far in the distance, and only placed near CG4 by chance superposition.

(NASA)  An Unusual Globule in IC 1396
Credit & Copyright: T. Rector (U. Alaska Anchorage) & H. Schweiker (WIYN, NOAO, AURA, NSF)

Is there a monster in IC 1396? Known to some as the Elephant’s Trunk Nebula, parts of gas and dust clouds of this star formation region may appear to take on foreboding forms, some nearly human. The only real monster here, however, is a bright young star too far from Earth to hurt us. Energetic light from this star is eating away the dust of the dark cometary globule near the top of the above image. Jets and winds of particles emitted from this star are also pushing away ambient gas and dust. Nearly 3,000 light-years distant, the relatively faint IC 1396 complex covers a much larger region on the sky than shown here, with an apparent width of more than 10 full moons.