Starship Asterisk*

Molecular Cloud Barnard 68

Explanation: Where did all the stars go? What used to be considered a hole in the sky is now known to astronomers as a dark molecular cloud. Here, a high concentration of dust and molecular gas absorb practically all the visible light emitted from background stars. The eerily dark surroundings help make the interiors of molecular clouds some of the coldest and most isolated places in the universe. One of the most notable of these dark absorption nebulae is a cloud toward the constellation Ophiuchus known as Barnard 68, pictured above. That no stars are visible in the center indicates that Barnard 68 is relatively nearby, with measurements placing it about 500 light-years away and half a light-year across. It is not known exactly how molecular clouds like Barnard 68 form, but it is known that these clouds are themselves likely places for new stars to form. In fact, Barnard 68 itself has been found likely to collapse and form a new star system. It is possible to look right through the cloud in infrared light.

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I wonder if Windex with ammonia will get that big black spot off?

How to Become a Star
ESO | eso0102 | 2001 Jan 10
Bok Globule B68

ESO Press Photo eso0102c shows a comparison of the central area of globule B68 in a colour composite of visible and near-infrared on the left and a false-colour composite based on a visible (here rendered as blue), a near-infrared (green) and an infrared (red) on the right.

Credit: ESO

It is amazing to consider that as dense as this object appears, at around a million particles per cubic centimeter (most of them being hydrogen molecules) this cloud is many orders of magnitude thinner and more transparent than our atmosphere.

Amazing what pollution can do for you, isn't it?

Whenever I see a picture of a molecular cloud, I am reminded of that Star Trek: TNG episode where Picard and crew are lost in a molecular cloud. A very scary and forbidding place.

But now that I see the infrared images, I wonder why Enterprise, the pride of 24th century Star Fleet, couldn't just have clicked on the infrared sensors and found their way out.

What a marvelous picture! But it kinda spoils that episode for me

But they did have a great warp drive.

What Chris pointed out about the thinness of this dark cloud is important.

Making new stars isn't easy. The cloud in today's APOD isn't up to it. The cloud really is far too thin and spread up to do that job. It is no wonder that the infrared photography of this cloud didn't reveal any pre-stellar cores in it.

EDIT: Okay, I just read bystander's link to the ESO page where some astronomers claim that Barnard 68 is on the verge of becoming unstable and contracting to the point that it will give rise to "a hot, low-mass star", according to the ESO page. That is a contradiction in terms, since low-mass stars aren't hot.

My impression, as I'm looking at this dark cloud, is that it looks too small to make any stars. The cloud isn't really elongated at all. My impression is that star formation often takes place along long dark thick "filaments" of dust. Take a look at this Spitzer Space Telescope infrared image of Orion, where you can see how new stars are being born along dusty filaments above the Orion Nebula. Barnard 68, by contrast, is too round in shape to look like promising star formation material, and it ends too abruptly.

If you change the number Barnard 68 into Barnard 86, you'll get a molecular cloud that is somewhat similar to this. What is so interesting about Barnard 86 is that you can see that this cloud is the more or less "dead" dusty remnant of previous star formation. The cluster to the lower left of Barnard 86, NGC 6520, was probably born out of "the mother cloud" that was spent in the process and left stars and the small dust cloud Barnard 86 behind.

Admittedly, cluster NGC 6520 has a thin dusty remnant "below" it, and it may be the this remnant that used to be the actual cloud that gave rise to NGC 6520. But if so, it is still likely that the dusty core that gave rise to NGC 6520 was once connected with what is Barnard 86 today.

You can see that NGC 6520 contains a red giant in the middle, so the cluster is at least old enough to have seen its most massive member use up all the hydrogen in its core and expand to a red giant. According to my software, which may or may not be absolutely reliable here, all the bright stars in this cluster may have used up all or most of their central hydrogen, which again suggests that the cluster isn't brand new. However, the blue star which is located between NGC 6520 and Barnard 86, and which appears to be surrounded by a swarm of small stars (but is not), may or may not be a younger star that was born slightly later out of the same dust cloud, and is still fusing hydrogen in its core.

What about the bright yellow-orange star on the other side of Barnard 86? I find it unlikely that this star was born out of the larger cloud that Barnard 86 is the remnant of. You can see that Barnard appears to end pretty abruptly on the side where the bright yellow star is, but remnants of it seem to extend quite far on the side of NGC 6520.

There are many small "barren" dust clouds like Barnard 68 and Barnard 86 in our galaxy. When you find them near young bright stars or clusters, you are probably right to think that these little clouds are the remnants of once mighty dense clouds that gave rise to huge stars and mighty clusters.

Ann

Could this be what the universe was like before the first stars were born?

http://www.eso.org/public/archives/imag ... o9934b.jpg

It blocks the smaller wavelengths, blue and smaller, but not the long wavelengths of the near-infrared and longer. What's up with that?! Can't detect any emissions from the cloud, only from the stars behind it. Is that black matter? Talking about tending toward maximum entropy, just how cold is it and how did it lose its molecular energy? It's bombarded with photons from all directions, yet none have an effect. It absorbs blue, ultraviolet, x-rays, you'd think that would warm it up a bit. Does it show up on the cosmic background radiation maps? Speaking of Star Trek, what if it's a lifeform....

Ann wrote:My impression, as I'm looking at this dark cloud, is that it looks too small to make any stars.

By "small" are you referring to physical dimensions, or to mass?

Certainly, with a couple of solar masses, there's enough material here to make a star. A useful (but no doubt far from perfect) rule is that when you see a sharply defined molecular cloud like this, it is probably collapsing, meaning there's a good chance of forming one or more stars. When you see a ragged cloud, it is probably dissipating, and no stars (or no more stars) will form.

Hello, happy Sunday afternoon.
The dark molecular cloud was once considered as a black hole,such concentration of dust, molecular gas all visible light emitted by stars that are at the bottom disappears, like the cold darknessinside the cloud must be terrible, because they quite isolated this place in the universe, is said to be dark nebula known as Barnard68, appears as does a beating heart to contract and expand. Itpredicts the birth of a star, studies say that this nebula will become a bright star within 200,000 years. It is also said that this nebula and is colliding with a smaller one, in a process that will conclude with star birth. As these molecular clouds are so black?
Greetings.

Chris wrote:
By "small" are you referring to physical dimensions, or to mass?

Good question. I guess I meant both. The cloud looked both relatively small in physical dimensions, although I admit that kind of thing is hard to judge. I also referred to mass. According to the ESO page, Barnard 68 contains about two solar masses. That doesn't seem like a lot to me at all. Obviously only a relatively small part of this comparatively small mass will go into forming a new star, if it will happen at all. I was thinking about puny Proxima Centauri, whose mass is something like 10-15% solar. So okay, maybe Barnard 68 can make another Proxima Centauri.

A useful (but no doubt far from perfect) rule is that when you see a sharply defined molecular cloud like this, it is probably collapsing, meaning there's a good chance of forming one or more stars. When you see a ragged cloud, it is probably dissipating, and no stars (or no more stars) will form.

Interesting. I hadn't thought of that. Good point, Chris.

Ann

Chris Peterson wrote:
When you see a ragged cloud, it is probably dissipating, and no stars (or no more stars) will form.

Around the ragged racks the rugged rascals ran.

Wonder is this is a remnant of the pre-Big Bang universe, before light began to spread. Or not !

wolf kotenberg wrote:Wonder is this is a remnant of the pre-Big Bang universe, before light began to spread. Or not !

Not!

Wonderful photo! When I first glimpsed it, I thought, "Einstein, what have you done now?"
It's nice to see the other spectrum shot showing the start behind the cloud.
And then, I thought of the ST:Voyager Episode "Night".
Creepy.
Clear skies, pleasant company,
-Andy.

neufer wrote:

Chris Peterson wrote:
When you see a ragged cloud, it is probably dissipating, and no stars (or no more stars) will form.

Around the ragged racks the rugged rascals ran.

T'was the ragged circles they wrought, with nary a thought.
The cloud was so dark, that they could not fight,
lest a bright star cometh forth and give them some light.
So we wait and we wait and we wait still,
Til the photons from then, the news they spill,
as to whether or not they got into a fight,
and caused a bright star, that gave them some light.

APOD Robot wrote: Molecular Cloud Barnard 68

Explanation: What used to be considered a hole in the sky is now known to astronomers as a dark molecular cloud.

That no stars are visible in the center indicates that Barnard 68 is relatively nearby,
with measurements placing it about 500 light-years away and half a light-year across.

http://en.wikipedia.org/wiki/NGC_1999 wrote:

---

<<NGC 1999 is a dust filled bright nebula with a vast hole of empty space represented by a black patch of sky, as can be seen in the photograph. It is a reflection nebula, and shines from the light of the variable star V380 Orionis.

It was previously believed that the black patch was a dense cloud of dust and gas which blocked light that would normally pass through, called a dark nebula. Analysis of this patch by the infrared telescope Herschel (October 9, 2009), which has the capability of penetrating such dense cloud material, resulted in continued black space. This led to the belief that either the cloud material was immensely dense or that an unexplained phenomenon had been detected.

With support from ground-based observations done using the submillimeter bolometer cameras on the Atacama Pathfinder Experiment radio telescope (November 29, 2009) and the Mayall (Kitt Peak) and Magellan telescopes (December 4, 2009), it was determined that the patch looks black not because it is an extremely dense pocket of gas, but because it is truly empty. The exact cause of this phenomenon is still being investigated, although it has been hypothesized that narrow jets of gas from some of the young stars in the region punctured the sheet of dust and gas, as well as, powerful radiation from a nearby mature star may have helped to create the hole. Researchers believe this discovery should lead to a better understanding of the entire star forming process.

It is located 1,500 light-years away from Earth in the constellation Orion.

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if it absorb all light and radiation why isn't it luminous it must be HOT and shining