APOD: Haunting the Cepheus Flare (2016 Oct 28)

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APOD: Haunting the Cepheus Flare (2016 Oct 28)

Post by APOD Robot » Fri Oct 28, 2016 4:05 am

Image Haunting the Cepheus Flare

Explanation: Spooky shapes seem to haunt this jeweled expanse, drifting through the night in the royal constellation Cepheus. Of course, the shapes are cosmic dust clouds faintly visible in dimly reflected starlight. Far from your own neighborhood on planet Earth, they lurk along the plane of the Milky Way at the edge of the Cepheus Flare molecular cloud complex some 1,200 light-years away. Over 2 light-years across and brighter than the other ghostly apparitions, vdB 141 or Sh2-136 is also known as the Ghost Nebula, seen at the right of the starry field of view. Within the nebula are the telltale signs of dense cores collapsing in the early stages of star formation.

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Re: APOD: Haunting the Cepheus Flare (2016 Oct 28)

Post by neufer » Fri Oct 28, 2016 4:52 pm

https://en.wikipedia.org/wiki/Ghost wrote: <<In English Renaissance theater, ghosts were often depicted in the garb of the living and even in armor, as with the ghost of Hamlet's father. Armor, being out-of-date by the time of the Renaissance, gave the stage ghost a sense of antiquity. But the sheeted ghost began to gain ground on stage in the 19th century because an armored ghost could not satisfactorily convey the requisite spookiness: it clanked and creaked, and had to be moved about by complicated pulley systems or elevators. These clanking ghosts being hoisted about the stage became objects of ridicule as they became clichéd stage elements. Ann Jones and Peter Stallybrass, in Renaissance Clothing and the Materials of Memory, point out, "In fact, it is as laughter increasingly threatens the Ghost that he starts to be staged not in armor but in some form of 'spirit drapery'.">>
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Re: APOD: Haunting the Cepheus Flare (2016 Oct 28)

Post by MarkBour » Fri Oct 28, 2016 6:27 pm

This is a great and spooky image!

From a few recent APODs, I have wandered into an area that is new to me. The question, in general, is how much of the in-principle-observable universe of EMR-emitting objects are we able to see (fairly clearly), and how much of it are we blocked from seeing, by the simplest of reasons, of having clouds intervening that are effectively opaque, or other objects which are opaque. Here I am saying opaque in the very empirical sense that there is a star or galaxy in a given direction, whose light has had time to reach us, but we don't see it in our telescopes because of what lies in between us and it. (I'm not talking about things we can get around, such as the Earth or Moon, or things that intervene occasionally, such as Jupiter. I'm talking about things that are far enough and sufficiently stable that we are truly at their mercy. We would not necessarily know they are there, but we also fail to see anything beyond them.)
Detail.JPG
A nice example from today's APOD is the excerpt at the right. It is clear that there are almost no stars shining through the dark brown patches to us, at least not visible in the image. Therefore, a survey of this region would be impoverished in its star count. I think this is a good example, because it is so opaque as to clearly show the point. But that also makes it a bad example in terms of subtlety. The most problematic case would be clouds that are subtle enough that we do not note them.

Chris pointed out that if there is too much of this going on, we would be able to tell of its occurrence because such clouds would glow in IR. Although I find this statement hard to contest if one imagines a simple curtain-like shield over a lot of bright objects, I'm not prepared to agree with that if one considers all the subtlety of arrangements that are possible in our huge, 3D universe, that it is indeed impossible that there is a significant amount of blockage out there that really does block light and that we cannot detect, or at least have not yet detected.

I don't know where I'm going with this, it just seems that I'd like to get a better handle on whether or not there could be this source of uncertainty. Also, whether or not one could make estimates of the issue and how one could hope to do so. If there is sufficient "hidden normal matter", then it would affect estimates of the amount of truly dark matter, I would think.
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Re: APOD: Haunting the Cepheus Flare (2016 Oct 28)

Post by Boomer12k » Fri Oct 28, 2016 8:11 pm

WIPE YOUR FEET!!!! You're getting the spaceship all DUSTY!!!! OI!!! YOU!!!!

A great Halloween sector of space...and a fine image.
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Re: APOD: Haunting the Cepheus Flare (2016 Oct 28)

Post by Boomer12k » Fri Oct 28, 2016 8:13 pm

Instead of "ghosts" of the DEAD... should they not be considered... Pre-Birth Material??? But I guess that is not so spooky....

"BOO!!!, I am almost born...."...yeah, not spooky enough...

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Re: APOD: Haunting the Cepheus Flare (2016 Oct 28)

Post by FLPhotoCatcher » Fri Oct 28, 2016 8:18 pm

At first I thought that the cone in the thick dust was from a star shooting through the dust cloud. But I see that there is another cone opposite it, so the cones must be from a star near the tips of the cones.
But it got me thinking. Years ago on this comment site, I noted that clouds of dust in front of a fast moving star would actually speed up the star, not slow it down, because the dust's gravity would pull the star more forward than backward due to the dust being piled-up in front of the star. The only slowing down the dust may cause would seem to be from more reflected light hitting the front of the star than the back of it. But I suppose the star could also slow down from more 'solar' wind emanating from the front (hotter) part of the star. Then I wondered what would happen if the star was rotating... Would the star's rotation allow the 'solar' wind to emanate more from the side than the front, thus causing the star to curve slightly like a spinning baseball?

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Re: APOD: Haunting the Cepheus Flare (2016 Oct 28)

Post by zendae1 » Fri Oct 28, 2016 10:20 pm

Is there a poster available for this particular image?

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Re: APOD: Haunting the Cepheus Flare (2016 Oct 28)

Post by Ann » Sat Oct 29, 2016 4:24 am

MarkBour wrote:This is a great and spooky image!

From a few recent APODs, I have wandered into an area that is new to me. The question, in general, is how much of the in-principle-observable universe of EMR-emitting objects are we able to see (fairly clearly), and how much of it are we blocked from seeing, by the simplest of reasons, of having clouds intervening that are effectively opaque, or other objects which are opaque. Here I am saying opaque in the very empirical sense that there is a star or galaxy in a given direction, whose light has had time to reach us, but we don't see it in our telescopes because of what lies in between us and it. (I'm not talking about things we can get around, such as the Earth or Moon, or things that intervene occasionally, such as Jupiter. I'm talking about things that are far enough and sufficiently stable that we are truly at their mercy. We would not necessarily know they are there, but we also fail to see anything beyond them.)
Detail.JPG
A nice example from today's APOD is the excerpt at the right. It is clear that there are almost no stars shining through the dark brown patches to us, at least not visible in the image. Therefore, a survey of this region would be impoverished in its star count. I think this is a good example, because it is so opaque as to clearly show the point. But that also makes it a bad example in terms of subtlety. The most problematic case would be clouds that are subtle enough that we do not note them.

Chris pointed out that if there is too much of this going on, we would be able to tell of its occurrence because such clouds would glow in IR. Although I find this statement hard to contest if one imagines a simple curtain-like shield over a lot of bright objects, I'm not prepared to agree with that if one considers all the subtlety of arrangements that are possible in our huge, 3D universe, that it is indeed impossible that there is a significant amount of blockage out there that really does block light and that we cannot detect, or at least have not yet detected.

I don't know where I'm going with this, it just seems that I'd like to get a better handle on whether or not there could be this source of uncertainty. Also, whether or not one could make estimates of the issue and how one could hope to do so. If there is sufficient "hidden normal matter", then it would affect estimates of the amount of truly dark matter, I would think.
I don't think dust can hide things from us very well, not with our IR-sensitive equipment that can see right through dust. With the launch of the new James Webb Space Telescope, dust simply stands no chance.

What worries me about the JWST is that it won't be able to see blue light at all. That means, for example, that JWST might be pretty useless when it comes to spotting new supernovas. At birth, supernovas are hot and ultraviolet, but JWST will probably not see them until they have cooled and reddened considerably, or until they have heated up dust in their environment.

And isn't it possible that deep space might produce such high-energy photons that they represent blue and ultraviolet light even when they reach us, after billions of years? James Webb will not be able to see them.

So I think it is quite possible that there are things out there that we can't see, just because our equipment isn't sensible enough. Personally I think that dust isn't much of a problem now and will become less so in the near future, but there might be other things that we simply haven't figured out and haven't got a clue how to pin down yet.

Such as dark matter. For example.

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Re: APOD: Haunting the Cepheus Flare (2016 Oct 28)

Post by Chris Peterson » Sat Oct 29, 2016 1:40 pm

Ann wrote:What worries me about the JWST is that it won't be able to see blue light at all. That means, for example, that JWST might be pretty useless when it comes to spotting new supernovas. At birth, supernovas are hot and ultraviolet, but JWST will probably not see them until they have cooled and reddened considerably, or until they have heated up dust in their environment.
Why does that worry you? Why is that a problem? Does it bother you that radio telescopes can't see blue light? Or that the Hubble can't detect radio waves? Instruments are optimized to cover a certain spectral range and sensitivity range. If you make them broader (assuming that's even possible) you compromise their design. We use combinations of instruments to extend our vision across wider ranges, not single instruments that need to do it all. It's not like JWST isn't backed up by a large number of instruments which are very sensitive to blue light.

Space telescopes are not optimal for detecting new supernovas. That's much better suited to ground-based optical survey instruments, of which a number are now operational.
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Re: APOD: Haunting the Cepheus Flare (2016 Oct 28)

Post by Ann » Sat Oct 29, 2016 3:43 pm

Chris Peterson wrote:
Ann wrote:What worries me about the JWST is that it won't be able to see blue light at all. That means, for example, that JWST might be pretty useless when it comes to spotting new supernovas. At birth, supernovas are hot and ultraviolet, but JWST will probably not see them until they have cooled and reddened considerably, or until they have heated up dust in their environment.
Why does that worry you? Why is that a problem? Does it bother you that radio telescopes can't see blue light? Or that the Hubble can't detect radio waves? Instruments are optimized to cover a certain spectral range and sensitivity range. If you make them broader (assuming that's even possible) you compromise their design. We use combinations of instruments to extend our vision across wider ranges, not single instruments that need to do it all. It's not like JWST isn't backed up by a large number of instruments which are very sensitive to blue light.

Space telescopes are not optimal for detecting new supernovas. That's much better suited to ground-based optical survey instruments, of which a number are now operational.
It worries me that Hubble, with its shortwave capabilities, is going to be replaced by an IR instrument. I'm not saying we don't need a cutting edge IR telescope, just that we need a top-class UV space telescope, too. Most importantly, we need an top class UV space telescope that isn't primarily devoted to solar observations.

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Re: APOD: Haunting the Cepheus Flare (2016 Oct 28)

Post by Chris Peterson » Sat Oct 29, 2016 4:33 pm

Ann wrote:It worries me that Hubble, with its shortwave capabilities, is going to be replaced by an IR instrument. I'm not saying we don't need a cutting edge IR telescope, just that we need a top-class UV space telescope, too. Most importantly, we need an top class UV space telescope that isn't primarily devoted to solar observations.
It would, of course, be nice to have the resources to build a wider range of instruments. But sadly, that isn't the case, so we have to put our money where best it serves, and it is increasingly clear that IR observations are the most valuable of all the visible range- more of the "big questions" in astronomy depend upon longer wavelength observations. So we have JWST.
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Re: APOD: Haunting the Cepheus Flare (2016 Oct 28)

Post by neufer » Sat Oct 29, 2016 4:40 pm

Chris Peterson wrote:
Ann wrote:
What worries me about the JWST is that it won't be able to see blue light at all. That means, for example, that JWST might be pretty useless when it comes to spotting new supernovas. At birth, supernovas are hot and ultraviolet, but JWST will probably not see them until they have cooled and reddened considerably, or until they have heated up dust in their environment.
Space telescopes are not optimal for detecting new supernovas. That's much better suited to ground-based optical survey instruments, of which a number are now operational.
Infrared space telescopes are useful for detecting/monitoring distant (cosmological redshifts z > 1) supernovas.
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Re: APOD: Haunting the Cepheus Flare (2016 Oct 28)

Post by Chris Peterson » Sat Oct 29, 2016 4:51 pm

neufer wrote:
Chris Peterson wrote:
Ann wrote:
What worries me about the JWST is that it won't be able to see blue light at all. That means, for example, that JWST might be pretty useless when it comes to spotting new supernovas. At birth, supernovas are hot and ultraviolet, but JWST will probably not see them until they have cooled and reddened considerably, or until they have heated up dust in their environment.
Space telescopes are not optimal for detecting new supernovas. That's much better suited to ground-based optical survey instruments, of which a number are now operational.
Infrared space telescopes are useful for detecting/monitoring distant (cosmological redshifts z > 1) supernovas.
To some extent. Nevertheless, no current (or currently considered) IR space telescopes are survey instruments. That means that they will miss most supernovas (just as the HST does, for that matter) unless data from some other instrument directs their observation. No doubt there will be occasional serendipitous discoveries of high redshift events.
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Re: APOD: Haunting the Cepheus Flare (2016 Oct 28)

Post by geckzilla » Sat Oct 29, 2016 5:08 pm

I think they've had pretty good luck finding supernovas serendipitously in the ultra deep fields. When failing to cover a large area of sky, a large number of young, star-forming galaxies in one small place will do, and JWST will certainly be able to do that.
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Re: APOD: Haunting the Cepheus Flare (2016 Oct 28)

Post by Chris Peterson » Sat Oct 29, 2016 5:18 pm

geckzilla wrote:I think they've had pretty good luck finding supernovas serendipitously in the ultra deep fields. When failing to cover a large area of sky, a large number of young, star-forming galaxies in one small place will do, and JWST will certainly be able to do that.
Yes, but those are of limited scientific value since they are generally identified quite a long time after the event. Supernovas are most valuable when detected early and tracked photometrically right away (which is also problematic for space telescopes, since their observing programs normally only support changes in allocated time for the most critical events).
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