Starship Asterisk*

starsurfer wrote:This is something I never expected to see on APOD! V1331 Cygni is one of many interesting stars associated with a nebula in this constellation, check this closeup by Adam Block. It's nice that the description also includes a link to the 2013 paper, Bo Reipurth is one of the best researchers (of many in the world) of star formation.

About T Tauri stars

T Tauri stars are named for the prototype of the class, T Tauri. These objects are pre-main sequence stars and have recently emerged from the opaque envelope of stellar formation. Having recently coalesced from their dusty and gaseous surroundings, these stars now become visible at optical wavelengths. The clouds of dust and gas that condense are composed of mainly Hydrogen, some Helium, and some other trace elements. The clouds also contain small amounts of Lithium which is usually destroyed as the star evolves to the main sequence stage of life. Hence, Lithium is often an indicator of stellar youth. This spectral feature is seen in the atmospheres of the T Tauri stars, which implies, in the astronomical sense, that T Tauri stars are a young, low-mass stars that are contracting as they evolve toward the main sequence stage of stellar evolution. These stars often have large protoplanetary accretion disks left over from stellar formation. The general belief is that T Tauri stars are newly forming stars in the galaxy and may be growing in size through accretion. Brightness changes detected in these stars are not due to evolutionary effects, per se, but may be due to such processes as instabilities in the disk, violent activity in the atmosphere of the star, and may also be due in part to moving clouds of dust and gas from which they were conceived. "Stars with masses roughly 0.2 to three times the Sun's and with ages 100,000 to 1,000,000 years typify the T Tauri regime" (Cohen 1981).

Many of the T Tauri stars are found to reside in or near areas that are hidden by the Milky Way clouds. "We now know why this is so: those stars were born in those dark clouds, within the last 10 million years or so, and there has not been enough time for them to move very far from their birthplaces" (Herbing 1987). The Taurus-Auriga dark cloud is a known hot-bed of such stars.

Our own Sun presumably passed through the T Tauri stage some 4 1/2 billion years ago. Therefore, these stars may be able to offer us a peek into the evolution of our own Sun, solar system, as well as other planetary systems.

BDanielMayfield wrote:

starsurfer wrote:This is something I never expected to see on APOD! V1331 Cygni is one of many interesting stars associated with a nebula in this constellation, check this closeup by Adam Block. It's nice that the description also includes a link to the 2013 paper, Bo Reipurth is one of the best researchers (of many in the world) of star formation.

Why did you never expect to see this on APOD starsurfer? Is it that images of dark clouds don't get the coverage they deserve perhaps? I note that it took all night for someone to comment about this. But I too am glad this image was provided. Following a chain of links led me to this about T-Tauri stars from the AAVSO:

About T Tauri stars

T Tauri stars are named for the prototype of the class, T Tauri. These objects are pre-main sequence stars and have recently emerged from the opaque envelope of stellar formation. Having recently coalesced from their dusty and gaseous surroundings, these stars now become visible at optical wavelengths. The clouds of dust and gas that condense are composed of mainly Hydrogen, some Helium, and some other trace elements. The clouds also contain small amounts of Lithium which is usually destroyed as the star evolves to the main sequence stage of life. Hence, Lithium is often an indicator of stellar youth. This spectral feature is seen in the atmospheres of the T Tauri stars, which implies, in the astronomical sense, that T Tauri stars are a young, low-mass stars that are contracting as they evolve toward the main sequence stage of stellar evolution. These stars often have large protoplanetary accretion disks left over from stellar formation. The general belief is that T Tauri stars are newly forming stars in the galaxy and may be growing in size through accretion. Brightness changes detected in these stars are not due to evolutionary effects, per se, but may be due to such processes as instabilities in the disk, violent activity in the atmosphere of the star, and may also be due in part to moving clouds of dust and gas from which they were conceived. "Stars with masses roughly 0.2 to three times the Sun's and with ages 100,000 to 1,000,000 years typify the T Tauri regime" (Cohen 1981).

Many of the T Tauri stars are found to reside in or near areas that are hidden by the Milky Way clouds. "We now know why this is so: those stars were born in those dark clouds, within the last 10 million years or so, and there has not been enough time for them to move very far from their birthplaces" (Herbing 1987). The Taurus-Auriga dark cloud is a known hot-bed of such stars.

Our own Sun presumably passed through the T Tauri stage some 4 1/2 billion years ago. Therefore, these stars may be able to offer us a peek into the evolution of our own Sun, solar system, as well as other planetary systems.

So people shouldn't overlook these dusty areas as of little interest. They are where new solar systems are being created.

Bruce

starsurfer wrote:... here is a list of some of dark nebulae I like:

LDN 673 by Adam Block: http://www.caelumobservatory.com/gallery/ldn673.shtml
Pipe Nebula by Jason Jennings: http://cosmicphotos.com/gallery/image.p ... lbum_id=11
Sandqvist 169 by Marco Lorenzi: http://www.glitteringlights.com/Images/ ... WVpcRqS/X3
B86 by Bernhard Hubl: http://www.astrophoton.com/NGC6520.htm
LDN 1003 by Antonio Sánchez: http://afesan.es/Deepspace/slides/LRGB% ... us%29.html
Bernes 149 by Fabian Neyer: http://www.starpointing.com/ccd/bernes149.html
Coalsack Nebula by Bernhard Hubl: http://www.astrophoton.com/coalsack.htm
Serpens Cloud by Tom Davis: http://www.tvdavisastropics.com/astroim ... 000101.htm
LDN 935 by Antonio Sánchez: http://afesan.es/Deepspace/slides/LRGB% ... us%29.html
B142 by Bernhard Hubl: http://www.astrophoton.com/B143.htm

dlw wrote:I'm wondering why some of the molecular clouds are long and narrow. The large amorphous clouds may be left overs from major events, and perhaps coalescing, seem rather normal. The long narrow ones such as the one in which V1331 Cyg is developing and also other clouds in that area would seem to have been formed by some more distinct physical phenomena.

V1331 Cyg clouds.jpg

BDanielMayfield wrote:

dlw wrote:I'm wondering why some of the molecular clouds are long and narrow. The large amorphous clouds may be left overs from major events, and perhaps coalescing, seem rather normal. The long narrow ones such as the one in which V1331 Cyg is developing and also other clouds in that area would seem to have been formed by some more distinct physical phenomena.

V1331 Cyg clouds.jpg

Good question. Why are so many molecular clouds long and narrow? There must be some common physical reason why this is such a common shape for these objects to condense into. Gravity is of course important, but there's got to be more than just gravity at work on them, or they would tend to be more spherical, I would think.

dlw wrote:I'm wondering why some of the molecular clouds are long and narrow.

BDanielMayfield wrote:starsurfer, wow, two most excellent postings today I had a most enjoyable lunch hour today perusing your favorite dark cloud images:

starsurfer wrote:... here is a list of some of dark nebulae I like:

LDN 673 by Adam Block: http://www.caelumobservatory.com/gallery/ldn673.shtml
Pipe Nebula by Jason Jennings: http://cosmicphotos.com/gallery/image.p ... lbum_id=11
Sandqvist 169 by Marco Lorenzi: http://www.glitteringlights.com/Images/ ... WVpcRqS/X3
B86 by Bernhard Hubl: http://www.astrophoton.com/NGC6520.htm
LDN 1003 by Antonio Sánchez: http://afesan.es/Deepspace/slides/LRGB% ... us%29.html
Bernes 149 by Fabian Neyer: http://www.starpointing.com/ccd/bernes149.html
Coalsack Nebula by Bernhard Hubl: http://www.astrophoton.com/coalsack.htm
Serpens Cloud by Tom Davis: http://www.tvdavisastropics.com/astroim ... 000101.htm
LDN 935 by Antonio Sánchez: http://afesan.es/Deepspace/slides/LRGB% ... us%29.html
B142 by Bernhard Hubl: http://www.astrophoton.com/B143.htm

starsurfer wrote:I aim to please, glad you enjoyed the images! I really like dark nebulae and in my opinion they are underrated. For next year I want to see more amateur images of dark nebulae taken with large telescopes, most images are widefield.

Chris Peterson wrote:

dlw wrote:I'm wondering why some of the molecular clouds are long and narrow.

I expect that the origin of these clouds lies in shells of material thrown off by cataclysmic stellar events like supernovas. That means that locally, they are originally sheet-like. We are going to see sheets as long and narrow, because only those that we observe largely end-on will be visible. In addition, over time, sheet-like structures will tend to collapse to rod-like structures and blob-like structures due to the actions of gravity.

Ann wrote:Wouldn't it be interesting if it had something to do with magnetism?

BDanielMayfield wrote:But is the collapse solely due to gravity? Ann raised an interesting conjecture:

Ann wrote:Wouldn't it be interesting if it had something to do with magnetism?

I think that the magnetic field strength way out in open space would be very weak. But, during the supernova events that largely create the metals forming all this dust magnetized grains of dust particles could form, and after cooling off the oppositely polarized ends of grains of dust would tend to stick together due to magnetism. Couldn't ionizing radiation also lead to charge differences that would help space dust clump together? Electrostatic forces between small particles are enormously greater than the gravitational attraction between them.

geckzilla wrote:

starsurfer wrote:I aim to please, glad you enjoyed the images! I really like dark nebulae and in my opinion they are underrated. For next year I want to see more amateur images of dark nebulae taken with large telescopes, most images are widefield.

The best are the ones with glowy things inside them. The recent HL Tauri press release happened within the dark blob next to Aldebaran which you can see very easily in this APOD.

geckzilla wrote:Coincidentally, I sprinkled a layer of cinnamon on top of some bubbling oatmeal a few moments ago, put the jar back in the cupboard, looked back at the oatmeal and it had formed dusty galactic filaments. No gravity or magnets required, just bubbles.

geckzilla wrote:That wouldn't work because it's a 2d analogue.