APOD: IC 1396: Emission Nebula in Cepheus (2012 Aug 05)

Comments and questions about the APOD on the main view screen.

APOD: IC 1396: Emission Nebula in Cepheus (2012 Aug 05)

Postby APOD Robot » Sun Aug 05, 2012 4:12 am

Image IC 1396: Emission Nebula in Cepheus

Explanation: Stunning emission nebula IC 1396 mixes glowing cosmic gas and dark dust clouds in the high and far off constellation of Cepheus. Energized by the bright, bluish central star seen here, this star forming region sprawls across hundreds of light-years -- spanning over three degrees on the sky while nearly 3,000 light-years from planet Earth. Among the intriguing dark shapes within IC 1396, the winding Elephant's Trunk nebula lies just below center. The gorgeous color view is a composition of digitized black and white photographic plates recorded through red and blue astronomical filters. The plates were taken using the Samuel Oschin Telescope, a wide-field survey instrument at Palomar Observatory, between 1989 and 1993.

<< Previous APOD This Day in APOD Next APOD >>
User avatar
APOD Robot
Otto Posterman
 
Posts: 1712
Joined: Fri Dec 04, 2009 3:27 am

Re: APOD: IC 1396: Emission Nebula in Cepheus (2012 Aug 05)

Postby Ann » Sun Aug 05, 2012 5:39 am

The Elephant's Trunk Nebula lies to the right of the bright central star in today's APOD.

It's interesting to look at this fine picture to try to judge, from pure visual appearance, the (relative) age of this nebula and its central powerhouse. IC 1396 is a typical emission nebula ionized by one or more hot stars of spectral class O or very early B.

All O stars are young, but they, too, go through phases of their evolution. Often you can make some sort of guess as to the age of the O stars based on the surrounding nebulosity (or lack of it).

IC 1396 is a large and comparatively faint nebula. The central star, HD 206267, is multiple. My software identifies at least three companion stars orbiting close to HD 206267, which may itself consist of at least two components.

Apart from the tight grouping of hot stars at the center of IC 1396, there is only a scattering of hot stars, quite widely separated from each other, inside the nebula.

The nebula itself looks relatively "smooth" near the center, although there are many dusty structures in the outer parts of it. The center has not been "blown out", and there is no "cavity" in the center. There is one obvious site of ongoing star formation in the larger nebula, which is, of course, the small part of the nebula called the Elephant's Trunk.

We may compare IC 1396 with the Lambda Orionis Nebula. Like IC 1396, the Lambda Orionis Nebula is a huge, faint structure with a tight grouping of hot stars in the center. However, unlike IC 1396, the Lambda Orionis Nebula is almost completely smooth, with no obvious dusty structures at all, and no sign of ongoing star formation. We may therefore infer that the Lambda Orionis Nebula is older than IC 1396, because the nebula is more "dispersed", and all star formation has ceased.

We can also compare IC 1396 with the Rosette Nebula. Unlike IC 1396, the Rosette Nebula has a very obvious cluster of hot stars at the center. Unlike IC 1396, the center of the Rosette Nebula has been "blown out", so that there is a cavity in the center. The outer parts of the Rosette contains many dusty structures, but there is no obvious star formation going on, and the Elephant's Trunk Nebula in IC 1396 has no obvious counterpart in the Rosette Nebula. We may therefore infer that the Rosette Nebula is older than IC 1396.

Another Nebula that warrants comparison is NGC 2264, powered by the central star S Monocerotis (S Mon). This nebula is not round, and its interior is turbulent. S Mon has blown out a small cavity around itself, but there is a lot of nebulosity close to it. There is not really a concentrated compact cluster in the nebula, but several young and relatively bright stars are scattered there. Obvious star formation is going on in the Cone Nebula. Because of the irregular appearance and all the central activity in this nebula, we may infer that it is younger than IC 1396.

It should be noted, too, that both S Mon and HD 206267 are somewhat faint as O stars go. This suggests that they are "unevolved" and therefore young. Both Meissa and the central stars of the Rosette nebula are intrinsically brighter, suggesting that they have grown brighter with age, as stars tend to do.

Ann
Color Commentator
User avatar
Ann
4725 Å
 
Posts: 5403
Joined: Sat May 29, 2010 5:33 am

Re: APOD: IC 1396: Emission Nebula in Cepheus (2012 Aug 05)

Postby Guest » Sun Aug 05, 2012 10:24 am

It looks like a giant cosmic nipple, I can't seem to turn away...
Guest
 

Re: APOD: IC 1396: Emission Nebula in Cepheus (2012 Aug 05)

Postby Lurker » Sun Aug 05, 2012 12:02 pm

In the lower right quadrant, as posted, there are three diagonal red lines. Are these processing artifacts or actual parts of the nebula? What mechanism would produce naturally occurring straight lines?
Lurker
 

Re: APOD: IC 1396: Emission Nebula in Cepheus (2012 Aug 05)

Postby neufer » Sun Aug 05, 2012 1:43 pm

APOD Robot wrote:Image IC 1396: Emission Nebula in Cepheus

The plates were taken using the Samuel Oschin Telescope, a wide-field survey instrument at Palomar Observatory, between 1989 and 1993.
http://www.jewishjournal.com/philanthro ... _20070126/ wrote:
Image

<<Samuel Oschin (1914– July 28, 2003), born in Detroit, was a Los Angeles entrepreneur and philanthropist. After generous donations the Samuel Oschin Planetarium at Griffith Observatory and the 48-inch Schmidt telescope at Mount Palomar Observatory were named for him. Cal Tech astronomer Michael Brown has recently used the Samuel Oschin telescope to discover new worlds in the dim reaches of the solar system beyond Pluto.

Golden lads and girls all must, as chimney-sweepers, come to dust.
- Guiderius (Cymbeline Act 4, Scene 2)

Samuel Oschin started out his business ventures "selling shoelaces and potato chips" and working as a chimney-sweeper. Before he had even finished elementary school, he had hired friends and transformed chimney-sweeping into a growing enterprise. He exceled as a painter, manufacturer and real estate developer. Oschin combined his entrepreneurial skill and community compassion to design low-income housing in L.A. with the Housing and Urban Development Agency. Oschin founded the Mr. and Mrs. Samuel Oschin Family Foundation in 1981, which helped to provide scholarships for disabled minority students at UCLA and Stanford University.

Some of Samuel Oschin's best-known and most exotic expeditions included retracing Robert Peary's voyage to the North Pole, paddling up the Amazon in a dugout canoe and crossing the Alps atop an elephant (à la Hannibal). Less well known is the central role his romance with the night sky played in his adventures. "He navigated by the stars when he traveled to these remote places," his widow, Lynda Oschin said. "That experience was as important to him as the trips themselves." "One year he took me to the desert near Lake Mead so we could watch the Perseid Meteor Shower in dry air with no light pollution," Lynda Oschin said. "Even before we saw the first meteor streak across the sky, I was dazzled just looking up at the night sky under those perfect conditions. When my husband told me there were more stars in the sky than there were grains of sand on the earth, I really understood how deep this passion for astronomy was in him.">>
Art Neuendorffer
User avatar
neufer
Abstruse Allusion Artificer
 
Posts: 11395
Joined: Mon Jan 21, 2008 1:57 pm
Location: Alexandria, Virginia

Re: APOD: IC 1396: Emission Nebula in Cepheus (2012 Aug 05)

Postby neufer » Sun Aug 05, 2012 1:46 pm

Guest wrote:
It looks like a giant cosmic nipple, I can't seem to turn away...

"There's a sucker born every minute"

http://en.wikipedia.org/wiki/There%27s_ ... ery_minute
Art Neuendorffer
User avatar
neufer
Abstruse Allusion Artificer
 
Posts: 11395
Joined: Mon Jan 21, 2008 1:57 pm
Location: Alexandria, Virginia

Re: APOD: IC 1396: Emission Nebula in Cepheus (2012 Aug 05)

Postby Psnarf » Sun Aug 05, 2012 2:33 pm

I like the fact that there are no tell-tale CCD spikes around the brighter stars. Back to the design board for CCD astrophotography. What we need is something like a controllable row-column matrix, much like DRAM and keyboards. If a pixel gets swamped, instead of surplus electrons spilling into its neighbors, the offending star it could be attenuated (and marked as such). That setting could be used for future analysis of the star, since we would know the maximum exposure.

[copied from chapter 3.14,159 of "Ludicrous Schemes and Artifices"]
User avatar
Psnarf
Science Officer
 
Posts: 227
Joined: Fri Feb 26, 2010 6:19 pm

Re: APOD: IC 1396: Emission Nebula in Cepheus (2012 Aug 05)

Postby Chris Peterson » Sun Aug 05, 2012 3:19 pm

Psnarf wrote:I like the fact that there are no tell-tale CCD spikes around the brighter stars. Back to the design board for CCD astrophotography. What we need is something like a controllable row-column matrix, much like DRAM and keyboards. If a pixel gets swamped, instead of surplus electrons spilling into its neighbors, the offending star it could be attenuated (and marked as such). That setting could be used for future analysis of the star, since we would know the maximum exposure.

Of course, there are CCD sensors that don't bloom. They are commonly used by amateurs for aesthetic imaging. The price for this convenience is a loss of linearity and reduced sensitivity, which is why they are not generally used for scientific imaging.

The sort of sensor you propose is impossible when implemented as a CCD, but already exists in the form of CMOS devices. They are used in astronomical applications like wavefront detectors (for adaptive optics), but not often for scientific imaging because of other limitations, primarily higher noise and reduced dynamic range (compared with CCDs). It is entirely possible that CMOS detectors will ultimately replace CCDs for scientific imaging, but so far, nothing comes close to CCDs for their dynamic range, low noise, and high sensitivity.
Chris

*****************************************
Chris L Peterson
Cloudbait Observatory
http://www.cloudbait.com
User avatar
Chris Peterson
Abominable Snowman
 
Posts: 8737
Joined: Wed Jan 31, 2007 11:13 pm
Location: Colorado, USA


Return to The Bridge: Discuss an Astronomy Picture of the Day

Who is online

Users browsing this forum: Bing [Bot], CommonCrawl [Bot], Exalead [Bot], Google Mobile [Bot], MSNbot Media and 11 guests