APOD: The Elephant's Trunk in IC 1396 (2015 Oct 13)

Comments and questions about the APOD on the main view screen.
User avatar
APOD Robot
Otto Posterman
Posts: 3212
Joined: Fri Dec 04, 2009 3:27 am

APOD: The Elephant's Trunk in IC 1396 (2015 Oct 13)

Post by APOD Robot » Tue Oct 13, 2015 4:09 am

Image The Elephant's Trunk in IC 1396

Explanation: Like an illustration in a galactic Just So Story, the Elephant's Trunk Nebula winds through the emission nebula and young star cluster complex IC 1396, in the high and far off constellation of Cepheus. Of course, the cosmic elephant's trunk is over 20 light-years long. This composite was recorded through narrow band filters that transmit the light from ionized hydrogen, sulfur, and oxygen atoms in the region. The resulting image highlights the bright swept-back ridges that outline pockets of cool interstellar dust and gas. Such embedded, dark, tendril-shaped clouds contain the raw material for star formation and hide protostars within the obscuring cosmic dust. Nearly 3,000 light-years distant, the relatively faint IC 1396 complex covers a large region on the sky, spanning over 5 degrees.

<< Previous APOD This Day in APOD Next APOD >>
[/b]

User avatar
felopaul
Ensign
Posts: 52
Joined: Mon Apr 29, 2013 7:14 pm
Location: Flagey (France)

Re: APOD: The Elephant's Trunk in IC 1396 (2015 Oct 13)

Post by felopaul » Tue Oct 13, 2015 6:56 am

Thank you, and Happy that you choose our picture, first time for us !!

User avatar
Ann
4725 Å
Posts: 8854
Joined: Sat May 29, 2010 5:33 am

Re: APOD: The Elephant's Trunk in IC 1396 (2015 Oct 13)

Post by Ann » Tue Oct 13, 2015 7:04 am

Congratulations! There are many excellent astrophotographers who grace this site. It's always a joy when one of them gets an APOD.

Ann
Color Commentator

User avatar
Ron-Astro Pharmacist
Resistored Fizzacist
Posts: 888
Joined: Thu Jan 03, 2013 10:34 pm
AKA: Fred
Location: Idaho USA

Re: APOD: The Elephant's Trunk in IC 1396 (2015 Oct 13)

Post by Ron-Astro Pharmacist » Tue Oct 13, 2015 3:55 pm

I love how you can see right through the "eye" of the elephant.

http://www.waid-observatory.com/ic1396-2012-10-27.html

It appears the "pupil" has moved. Has the dust cloud moved significantly between images? Maybe just a higher resolution?
Make Mars not Wars

starsurfer
Stellar Cartographer
Posts: 3106
Joined: Thu Mar 15, 2012 7:25 pm

Re: APOD: The Elephant's Trunk in IC 1396 (2015 Oct 13)

Post by starsurfer » Tue Oct 13, 2015 5:23 pm

This is an incredibly detailed image, well done to everyone involved! The Elephant Trunk Nebula is one of many bright rimmed globules, others can be seen near the top of the image. Another object to mention is the wonderful dark nebula B163 near the top left corner.

Boomer12k
:---[===] *
Posts: 2243
Joined: Sun Apr 22, 2007 12:07 am

Re: APOD: The Elephant's Trunk in IC 1396 (2015 Oct 13)

Post by Boomer12k » Tue Oct 13, 2015 6:12 pm

And excellent image!!

The LOWER PART....looks like the Statue of Liberty...raised arm, etc...
OHHHHHHH!!!! There I go again.... :lol2:

:---[===] *

Boomer12k
:---[===] *
Posts: 2243
Joined: Sun Apr 22, 2007 12:07 am

Re: APOD: The Elephant's Trunk in IC 1396 (2015 Oct 13)

Post by Boomer12k » Tue Oct 13, 2015 6:15 pm

Ron-Astro Pharmacist wrote:I love how you can see right through the "eye" of the elephant.

http://www.waid-observatory.com/ic1396-2012-10-27.html

It appears the "pupil" has moved. Has the dust cloud moved significantly between images? Maybe just a higher resolution?
Me thinks your perception is just off...
but that is a great close up image...

:---[===] *

FLPhotoCatcher
Science Officer
Posts: 144
Joined: Wed Jul 18, 2012 6:51 am

Re: APOD: The Elephant's Trunk in IC 1396 (2015 Oct 13)

Post by FLPhotoCatcher » Wed Oct 14, 2015 3:13 am

I know that most of the mass of the dust in the pictured nebula is hydrogen, but what if less than 25% was hydrogen? Has anyone figured what would happen if dust that low in hydrogen combined to make an object approximately the mass of our sun? Would you have something that looked and acted like a star?

User avatar
Ann
4725 Å
Posts: 8854
Joined: Sat May 29, 2010 5:33 am

Re: APOD: The Elephant's Trunk in IC 1396 (2015 Oct 13)

Post by Ann » Wed Oct 14, 2015 4:27 am

FLPhotoCatcher wrote:I know that most of the mass of the dust in the pictured nebula is hydrogen, but what if less than 25% was hydrogen? Has anyone figured what would happen if dust that low in hydrogen combined to make an object approximately the mass of our sun? Would you have something that looked and acted like a star?
I am not the best person to answer that question, but what I do know is that hydrogen is fantastically good at producing energy through fusion. All other elements (except perhaps lithium) require higher temperatures before they will produce energy through fusion.

So I guess that a universe that contained only 25% hydrogen, but contained the same mass as our own universe does, would be generally worse at making stars. By "stars", I mean objects that shine by their own light through fusion. Or perhaps the universe would have been just as good at making stars as it is today, but its stars would have had shorter lifetimes. Since stars spend most of their lifetimes fusing hydrogen into helium, the 25% hydrogen stars would use up their hydrogen sooner and have shorter lifetimes than the 75% hydrogen stars, or so I think.

The reason why massive stars in our 75% hydrogen universe have short lifetimes is because their cores get so hot due to their great mass, and they have to fuse their hydrogen at a furious rate to combat their own gravity. In a 25% hydrogen universe, a 25% hydrogen massive star would still have to produce a lot of energy to fight its own gravity and prevent itself from collapsing, but now it would have only a third of the hydrogen available to fight its own great mass.

So if our own Sun had started out life with the same mass as today, but with only 25% hydrogen, its core temperature would have been the same as today. The Sun would also have had to fuse hydrogen at the same rate as today in order to fight its own gravity, but since it would contain only a third of the hydrogen that our own Sun does, its core hydrogen might have been used up three times faster. Humanity might not have evolved fast enough in a 25% hydrogen universe to see a stable main sequence Sun. The 25% hydrogen Sun would have turned into a red giant with no difficulties, and if the Sun's core helium supply had been considerably greater than it will be in our present-day 75% hydrogen universe, it is just possible that its red giant lifetime (where stars primarily fuse helium) might have been longer.

But I think that on the whole, the Sun would have been a less suitable host for habitable planets in a 25% hydrogen universe than it is today.

Ann
Color Commentator

User avatar
Chris Peterson
Abominable Snowman
Posts: 13805
Joined: Wed Jan 31, 2007 11:13 pm
Location: Guffey, Colorado, USA

Re: APOD: The Elephant's Trunk in IC 1396 (2015 Oct 13)

Post by Chris Peterson » Wed Oct 14, 2015 2:50 pm

FLPhotoCatcher wrote:I know that most of the mass of the dust in the pictured nebula is hydrogen, but what if less than 25% was hydrogen? Has anyone figured what would happen if dust that low in hydrogen combined to make an object approximately the mass of our sun? Would you have something that looked and acted like a star?
I think it becomes an extreme example of a "what if" question given that a dust cloud like this lacks (by a substantial amount) the mass to come together under self-gravity and produce a protostar. So what you're really asking is what are the fusion paths available for the heavier elements found in interstellar dust. Most of these are understood for the major dust components (oxygen, silicon, carbon), but the way they fuse in a massive star is probably very different that what you'd see if they were all mixed together. I'd say that while the fusion reactions are at least partly understood, nobody knows how a star like this would actually look, because nobody has tried modeling one.
Chris

*****************************************
Chris L Peterson
Cloudbait Observatory
http://www.cloudbait.com

FLPhotoCatcher
Science Officer
Posts: 144
Joined: Wed Jul 18, 2012 6:51 am

Re: APOD: The Elephant's Trunk in IC 1396 (2015 Oct 13)

Post by FLPhotoCatcher » Wed Oct 14, 2015 7:21 pm

Chris Peterson wrote:
FLPhotoCatcher wrote:I know that most of the mass of the dust in the pictured nebula is hydrogen, but what if less than 25% was hydrogen? Has anyone figured what would happen if dust that low in hydrogen combined to make an object approximately the mass of our sun? Would you have something that looked and acted like a star?
I think it becomes an extreme example of a "what if" question given that a dust cloud like this lacks (by a substantial amount) the mass to come together under self-gravity and produce a protostar. So what you're really asking is what are the fusion paths available for the heavier elements found in interstellar dust. Most of these are understood for the major dust components (oxygen, silicon, carbon), but the way they fuse in a massive star is probably very different that what you'd see if they were all mixed together. I'd say that while the fusion reactions are at least partly understood, nobody knows how a star like this would actually look, because nobody has tried modeling one.
I don't think it's an extreme example of a "what if" question. In the far future, wouldn't the percentage of hydrogen sink below 25%? And what about if several massive planets combined? It seems to me that it would be something scientists would be interested in modeling.

User avatar
Chris Peterson
Abominable Snowman
Posts: 13805
Joined: Wed Jan 31, 2007 11:13 pm
Location: Guffey, Colorado, USA

Re: APOD: The Elephant's Trunk in IC 1396 (2015 Oct 13)

Post by Chris Peterson » Wed Oct 14, 2015 8:51 pm

FLPhotoCatcher wrote:
Chris Peterson wrote:I think it becomes an extreme example of a "what if" question given that a dust cloud like this lacks (by a substantial amount) the mass to come together under self-gravity and produce a protostar. So what you're really asking is what are the fusion paths available for the heavier elements found in interstellar dust. Most of these are understood for the major dust components (oxygen, silicon, carbon), but the way they fuse in a massive star is probably very different that what you'd see if they were all mixed together. I'd say that while the fusion reactions are at least partly understood, nobody knows how a star like this would actually look, because nobody has tried modeling one.
I don't think it's an extreme example of a "what if" question. In the far future, wouldn't the percentage of hydrogen sink below 25%? And what about if several massive planets combined? It seems to me that it would be something scientists would be interested in modeling.
The reason it's extreme is because without hydrogen clouds, there's nothing to hold things together. The dust will be far too diffuse. (Not that I think we'll see much decline in hydrogen, however. Most of the hydrogen in the Universe is not in stars, after all. We are unable to measure a difference in the amount of primordial hydrogen and the amount now observed because only a tiny fraction has been removed.)
Chris

*****************************************
Chris L Peterson
Cloudbait Observatory
http://www.cloudbait.com