APOD: An Unusual Globule in IC 1396 (2014 Apr 14)

[APOD Robot]

An Unusual Globule in IC 1396

Explanation: 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.

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[Nitpicker]

Stunning. (Especially the hi-res version.)

It took me a surprisingly long time to spot IC1396A (as shown in this APOD) within the much wider image of IC1396 provided in the first link. It also took me a while to realise that the monster star, HD 206267, is not within the frame of this APOD.

[Boomer12k]

Nice contrast with the orange background, and very clear....

:---[===] *

[zbvhs]

"Eating away the dust" What does that mean? Consuming somehow or merely pushing aside?

[neufer]

"Eating away the dust" What does that mean? Consuming somehow or merely pushing aside?

• Ionizing and pushing aside:

Energetic ultraviolet light from nearby hot stars has molded the globules and ionized their bright rims.

<<The "Pillars of Creation" are composed of cool molecular hydrogen and dust that are being eroded by photoevaporation from the ultraviolet light of relatively close and hot stars. The finger-like protrusions at the top of the clouds are made visible by the shadows of Evaporating Gaseous Globules (EGGs), which shields the gas behind them from intense UV flux. EGGs are themselves incubators of new stars. An evaporating gas globule or EGG is a region of hydrogen gas approximately 100 astronomical units in size, such that gases shaded by it are shielded from ionizing UV rays. Dense areas of gas shielded by an evaporating gas globule can be conducive to the birth of stars.

[b][color=#0000FF]Photoevaporation occurring to a protoplanetary disk due to the presence of a nearby O-type star[/color][/b]

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Photoevaporation denotes the process when a planet is stripped of its atmosphere (or parts of the atmosphere) due to high energy photons and other electromagnetic radiation. If a photon interacts with an atmospheric molecule, the molecule is accelerated and its temperature increased. If sufficient energy is provided, the molecule or atom may reach the escape velocity of the planet and "evaporate" into space. The lower the mass number of the gas, the higher the velocity obtained by interaction with a photon. Thus hydrogen is the gas which is most prone to photoevaporation.>>

[starsurfer]

This is the first time I have seen it described as a cometary globule. This is incorrect and it is one example of a bright rimmed globule. Some interesting papers:
http://www.aanda.org/articles/aa/abs/20 ... 11-12.html
http://iopscience.iop.org/0004-637X/690/1/683/
http://www.konkoly.hu/staff/kun/handboo ... EPHEUS.pdf

Also the reason it is a little difficult to find it in a widefield image of the whole of IC 1396 is because it isn't oriented north up.

[Psnarf]

APOD Job Security: Discovery of such wonders will never cease. How do you choose a thesis topic when there is so much 'there' there?

[neufer]

This is the first time I have seen it described as a cometary globule.
This is incorrect and it is one example of a bright rimmed globule.

<<The word comet derives from the Old English cometa from the Latin comēta or comētēs. That, in turn, is a latinisation of the Greek κομήτης ("wearing long hair"), and the Oxford English Dictionary notes that the term (ἀστὴρ) κομήτης already meant "long-haired star, comet" in Greek. Κομήτης was derived from κομᾶν ("to wear the hair long"), which was itself derived from κόμη ("the hair of the head") and was used to mean "the tail of a comet".>>

<<Coma is the nebulous envelope around the nucleus of a comet. It is formed when the comet passes close to the Sun on its highly elliptical orbit; as the comet warms, parts of it sublimate. This gives a comet a "fuzzy" appearance when viewed in telescopes and distinguishes it from stars. The word coma comes from the Greek "kome", in Greek written as κόμη, and can be translated as "hair".>>

[Chris Peterson]

APOD Job Security: Discovery of such wonders will never cease. How do you choose a thesis topic when there is so much 'there' there?

I predict that in another year or two we will have seen everything there is to see, discovered everything there is to discover, know everything there is to know. Then the APOD editors can retire. There are only a handful of thesis topics still remaining, so choose quickly!

[Ron-Astro Pharmacist]

APOD Job Security: Discovery of such wonders will never cease. How do you choose a thesis topic when there is so much 'there' there?

I predict that in another year or two we will have seen everything there is to see, discovered everything there is to discover, know everything there is to know. Then the APOD editors can retire. There are only a handful of thesis topics still remaining, so choose quickly!

Chris – I think you know a lot more than I'll ever contemplate knowing about much of physics and astronomy but that statement sounds a lot like the Munich physics professor Philipp von Jolly when he advised Max Planck against going into physics - saying, "In this field, almost everything is already discovered, and all that remains is to fill a few holes." (From the Wiki page on Max Plank)
As in everything- time will tell.

[Chris Peterson]

Chris – I think you know a lot more than I'll ever contemplate knowing about much of physics and astronomy but that statement sounds a lot like the Munich physics professor Philipp von Jolly when he advised Max Planck against going into physics - saying, "In this field, almost everything is already discovered, and all that remains is to fill a few holes."

What... you disagree?

[MarkBour]

Hmmmm ... I wasn't aware that Chris had a sarcastic side. That's a new APOD discovery in itself.

Tonight, I see our weather is gloomy and overcast. I was able to predict that weeks ago, based on the high correlation between neat events like a full Lunar eclipse with Mars in opposition nearby, and weather blocking it out in my area. Can anyone give me a ride up to Hubble tonight, where I can view it from above the clouds? I'd accept the ride from almost anyone, just not George Clooney.

[Chris Peterson]

Hmmmm ... I wasn't aware that Chris had a sarcastic side.

I don't.

[Nitpicker]

I predict that in another year or two we will have seen everything there is to see, discovered everything there is to discover, know everything there is to know. Then the APOD editors can retire. There are only a handful of thesis topics still remaining, so choose quickly!

But don't worry. Once civilisation collapses (perhaps from boredom), a lot of science will probably have to be redone in order to build things up again. Ah, the cycle of life. Today's science, if it can be recorded and successfully archived, might even appear as mystical hogwash to Earthlings of the distant future. (Though not sure if that would reflect badly on us or them.)

[geckzilla]

Well, if we run out of new things to learn about space, we can switch it over to Arthropod Picture of the Day. There are probably still a few million unknown species of them running around.

[Nitpicker]

That is already part of the arthropods' secret plan for total world domination.

[neufer]

[b][color=#0000FF]Hubble Space Telescope's first high-resolution ultraviolet and visible imaging of the Apollo 17 site in the Taurus-Littrow Valley. Credit: NASA/ESA/HST Moon Team[/color][/b]

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Can anyone give me a ride up to Hubble tonight, where I can view [the lunar eclipse] from above the clouds? I'd accept the ride from almost anyone, just not George Clooney.

I get it. It's nice up there. You can just shut down all the systems, turn out all the lights, and just open your eyes.
There are no clouds up there that can thwart you.

<<The moon is a difficult target for Hubble because it moves across the sky faster than Hubble can track it and is very dim in ultraviolet light. The observations required steady, precise, as well as long exposures to search for resources. In spite of these challenges, Hubble was able to image all of its targets, and early results show that Hubble can detect ilmenite at the Apollo 17 site from 400,000 km away.>>

• The Hubble lunar conspiracy

[neufer]

Well, if we run out of new things to learn about space, we can switch it over to Arthropod Picture of the Day. There are probably still a few million unknown species of them running around.

That is already part of the arthropods' secret plan for total world domination.

[Beyond]

Once the arthropods have total world control, they will be starting their own restaurants called... Red Human.

[MarkBour]

I spoke too soon. Although we were socked in with a spring snowstorm most of the evening on 14.04.14, by midnight it had passed and the clouds soon parted over my location in Central Illinois. That eclipse was utterly fantastic. Best I've ever seen.

[DavidLeodis]

The image seemed familiar and I wanted to know when it was acquired, but on doing a search of the APOD archive it did not seem to have been used before so I found some Exif data through the APOD image properties (if the Exif data was available through the image in the NOAO website I could not obtain any). In the APOD image Exif data it stated "Create Date 2012:02:02 16:41:11-09:00...Modify Date 2013:07:17 10:12:14-07:00...Temporal Start Time 2009:11:11 02:07". Could someone please let me know what "Temporal Start Time" is, which here is about 2 years 3 months before the Exif "Create Date"! Thanks in anticipation.

[Chris Peterson]

The image seemed familiar and I wanted to know when it was acquired, but on doing a search of the APOD archive it did not seem to have been used before so I found some Exif data through the APOD image properties (if the Exif data was available through the image in the NOAO website I could not obtain any). In the APOD image Exif data it stated "Create Date 2012:02:02 16:41:11-09:00...Modify Date 2013:07:17 10:12:14-07:00...Temporal Start Time 2009:11:11 02:07". Could someone please let me know what "Temporal Start Time" is, which here is about 2 years 3 months before the Exif "Create Date"! Thanks in anticipation.

I think it's a custom tag used by Flickr.

Since this image wasn't collected with software that builds an EXIF header, and since it is rare for software that converts FITS files to JPEG to attempt constructing such a header, I'd be skeptical that there's any useful information to be found that way. Any EXIF data is likely to reflect processing and conversion operations, and is totally disconnected from the original image capture.

[DavidLeodis]

Thanks Chris for that very helpful information.