APOD: Sharpless 308: Star Bubble (2019 Jan 31)

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APOD: Sharpless 308: Star Bubble (2019 Jan 31)

Post by APOD Robot » Thu Jan 31, 2019 5:08 am

Image Sharpless 308: Star Bubble

Explanation: Blown by fast winds from a hot, massive star, this cosmic bubble is huge. Cataloged as Sharpless 2-308 it lies some 5,200 light-years away toward the constellation of the Big Dog (Canis Major) and covers slightly more of the sky than a Full Moon. That corresponds to a diameter of 60 light-years at its estimated distance. The massive star that created the bubble, a Wolf-Rayet star, is the bright one near the center of the nebula. Wolf-Rayet stars have over 20 times the mass of the Sun and are thought to be in a brief, pre-supernova phase of massive star evolution. Fast winds from this Wolf-Rayet star create the bubble-shaped nebula as they sweep up slower moving material from an earlier phase of evolution. The windblown nebula has an age of about 70,000 years. Relatively faint emission captured in the expansive image is dominated by the glow of ionized oxygen atoms mapped to a blue hue. SH2-308 is also known as The Dolphin Nebula.

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Ann
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Re: APOD: Sharpless 308: Star Bubble (2019 Jan 31)

Post by Ann » Thu Jan 31, 2019 8:18 am

I found a pretty interesting widefield image of this stellar bubble.

Ann
Last edited by Ann on Thu Jan 31, 2019 4:33 pm, edited 1 time in total.
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Re: APOD: Sharpless 308: Star Bubble (2019 Jan 31)

Post by De58te » Thu Jan 31, 2019 8:29 am

For a second there as I looked at the image I thought, hey it kind of looks like the head of Flipper (a TV show starring a dolphin), except the eye in the center is anatomically too low down. AND THEN I read the APOD description to the end.

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Re: APOD: Sharpless 308: Star Bubble (2019 Jan 31)

Post by mjsakers » Thu Jan 31, 2019 1:27 pm

How do we know for sure that the bright star in the "center" is really the source star and not a background star that just happens to appear in the center? I can't imagine we can estimate distances accurately enough to know that for certain.

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Re: APOD: Sharpless 308: Star Bubble (2019 Jan 31)

Post by Chris Peterson » Thu Jan 31, 2019 2:09 pm

mjsakers wrote:
Thu Jan 31, 2019 1:27 pm
How do we know for sure that the bright star in the "center" is really the source star and not a background star that just happens to appear in the center. I can't imagine we can estimate distances accurately enough to know that for certain.
The formation of this young nebula requires the presence of a large, hot star at its center... and that's the only candidate.
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Re: APOD: Sharpless 308: Star Bubble (2019 Jan 31)

Post by starsurfer » Thu Jan 31, 2019 2:36 pm

We have Dean Salman and Don Goldman to thank for popularising this amazing deep sky object!
Also the nebula on the left is Sh2-303.

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Re: APOD: Sharpless 308: Star Bubble (2019 Jan 31)

Post by neufer » Thu Jan 31, 2019 3:05 pm

Chris Peterson wrote:
Thu Jan 31, 2019 2:09 pm
mjsakers wrote:
Thu Jan 31, 2019 1:27 pm

How do we know for sure that the bright star in the "center" is really the source star and not a background star that just happens to appear in the center. I can't imagine we can estimate distances accurately enough to know that for certain.
The formation of this young nebula requires the presence of a large, hot star at its center... and that's the only candidate.
https://en.wikipedia.org/wiki/Wolf%E2%80%93Rayet_star wrote:
<<Wolf–Rayet stars, often abbreviated as WR stars, are a rare heterogeneous set of stars with unusual spectra showing prominent broad emission lines of highly ionised helium and nitrogen or carbon. The spectra indicate very high surface enhancement of heavy elements, depletion of hydrogen, and strong stellar winds. Their surface temperatures range from 30,000 K to around 200,000 K, hotter than almost all other stars.>>
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Re: APOD: Sharpless 308: Star Bubble (2019 Jan 31)

Post by neufer » Thu Jan 31, 2019 3:07 pm

De58te wrote:
Thu Jan 31, 2019 8:29 am

For a second there as I looked at the image I thought, hey it kind of looks like the head of Flipper (a TV show starring a dolphin), except the eye in the center is anatomically too low down. AND THEN I read the APOD description to the end.
There's a porpoise to reading the APOD descriptions to the end.
Art Neuendorffer

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Re: APOD: Sharpless 308: Star Bubble (2019 Jan 31)

Post by orin stepanek » Thu Jan 31, 2019 7:26 pm

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Re: APOD: Sharpless 308: Star Bubble (2019 Jan 31)

Post by orin stepanek » Thu Jan 31, 2019 7:32 pm

A bubble stops being a bubble when it bursts :wink: :lol2:

Can a space bubble burst?
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Re: APOD: Sharpless 308: Star Bubble (2019 Jan 31)

Post by MarkBour » Thu Jan 31, 2019 9:46 pm

Some Basic astronomy questions, if you will.

We look at this image, and can see a blue bubble, which is the result of processing some data that "is dominated by the glow of ionized oxygen". Can someone help me better understand this? I'm thinking that ...
  1. There is a particular wavelength of light that comes from the event of an electron dropping from an excited state to its base orbital in an Oxygen atom. Perhaps this is the [O III] emission line at 500.7 nm.
  2. This image is thus taken by observing a very tight frequency band, mapping the points where it is seen to this light blue color in the image, and seeing that this forms a nice, approximately circular shape on the field of view. (Simple geometry at a distance that we think we already know, gives it a diameter of 60 Lyr.)
  3. Using this shape -- and I can see that it also has subtlety of "shading", which is either an intensity difference, or a density-of-blue-pixels difference -- our built-in visual cortex processing and associated higher reasoning decides that this is probably a sphere in 3-D (... with a bit of a dolphin-nose irregularity at the upper left).
So we conclude that there is a spherical boundary of Oxygen here.

Some of the myriad of questions I need to answer or learn to set aside, if I am going to "get off of the ground floor of astronomy", are:

Do images like this just lead us neophytes by the hand ?
  1. I assume it is reasonable to conclude that the majority of Oxygen in the region photographed has this distribution ... it is mainly a spherical surface. There is, by comparison, almost no Oxygen in the interior of the surface (way less, anyway). There is not much Oxygen outside the surface. This is less clear to me, because a ways outside the surface, one is farther from the energizing star, so it could perhaps be out there, just not getting excited.
  2. There could be lots of other elements having similar, or even quite different shapes of distribution in this region. We are just selectively looking at the Oxygen. Is there any statement along with an image like this, to the effect of: "We looked at lots of other wavelengths and did not see much of interest." (?) Or should I still be wondering about the distribution of Hydrogen, Carbon, Magnesium, ... Silicon, Iron, etc. in this region? Perhaps with more images at wavelengths appropriate to other elements we would find that there is a bubble of Nitrogen that is different, but interesting in comparison to the Oxygen bubble. (Maybe this is one concern that I should just "set aside".)

    The caption hinted that this Oxygen bubble exists, because the Oxygen that was emitted by the star, has met some resistance, so it is building up in a wave front as it expands away from the star.
  3. Does this imply there is a significant amount of some other material involved here? Do we know what that material would be? Does it have a characteristic signature by which we can detect its presence? Is it common outside of the bubble, but less so inside it, as the Oxygen has swept it outward? Do we know anything about its composition or density, or do we care?
  4. Does this spherical bubble shape point back to a single event of an Oxygen blast, or is it likely just a steady emission (wind), and the build-up is because of the resistance only? So is more Oxygen being emitted by the star today, just as it has been for a long time, or is it indicative of a single short-lived event (which for stars could mean quite a range of time intervals ... an "explosion" can probably take years in some cases, a "burst of Oxygen release" could perhaps be 100 years, in this image).
I mean, it is too easy for an amateur to look at an image and caption like this and say:
"Oh, this star suddenly blew out a bunch of Oxygen (and nothing else) on a violent day 70,000 years ago (maybe plus light travel time to Earth)."

I assume even professionals grapple some with questions like the above, but I have the feeling that if I better understood more precisely what statements are being made and what are just my mistaken assumptions about the process, the findings, the careful thinking behind various conclusions, etc. then I would be better able to learn what I really can from an image such as this.

Thanks for reading, and thanks for any replies.
Mark Goldfain

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Goldfain's multipart question sucking all the oxygen out of this thread?

Post by neufer » Thu Jan 31, 2019 10:00 pm

  • We're only really good with simple "Why is the sky blue" type questions.
https://www.sciencealert.com/this-new-material-can-suck-all-the-oxygen-out-of-a-room wrote:
New material can suck all the oxygen out of a room
SCIENCEALERT STAFF 2 OCT 2014

<<Scientists from the University of Southern Denmark have developed a new form of crystalline cobalt salt that acts like a super-effective oxygen sponge. Once it sucks up oxygen, it will hold on to it indefinitely until it's gently heated or exposed to low oxygen pressure, at which point it will quietly release its oxygen hoard back out into the atmosphere. About 10 litres of it would be needed to suck all of the oxygen out of an average-sized room. "The material can absorb and release oxygen many times without losing the ability. It is like dipping a sponge in water, squeezing the water out of it and repeating the process over and over again,” said lead researcher and nanobioscience professor Christine McKenzie, in a press release. "When the substance is saturated with oxygen, it can be compared to an oxygen tank, containing pure oxygen under pressure. The difference is that this material can hold three times as much oxygen."

The key to the material’s success in trapping and holding such a large amount of oxygen molecules is its lattice crystalline structure, says Michael Byrne at Motherboard: "Each single crystal structure features two nitrate ions bound to a metallic molecular substructure, like a nitrogen house built on a cobalt foundation. It's really a nitrogen mobile home, however, as the introduction of oxygen to the neighbourhood means the nitrogen ions very quickly split town. The oxygen ions then set up shop themselves on the cobalt foundation."

Once the material is heated up or the pressure in the environment is lowered just enough, the oxygen will move back out into the atmosphere and the nitrogen will move back into the lattice structure of cobalt material.

The team is hoping to use the new material to replace hefty oxygen tanks used by scuba divers and mountain climbers, plus it could have a huge effect on medical treatments, such as for patients with Chronic obstructive pulmonary disease (COPD), which right now requires them to be hooked up to a large oxygen tank 24 hours a day. What the researchers envision is a small, simple oxygen mask made from oxygen-packed cobalt material that constantly replenishes its supply.

The research has been published in the journal Chemical Science.>>
Art Neuendorffer

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Re: APOD: Sharpless 308: Star Bubble (2019 Jan 31)

Post by Fred the Cat » Fri Feb 01, 2019 4:35 am

Like any spontaneous event, it does question if its elements are ejected at the same rate or if a hierarchy develops dependent on their physical characteristics :?:
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Re: Goldfain's multipart question sucking all the oxygen out of this thread?

Post by Ann » Fri Feb 01, 2019 4:57 am

neufer wrote:
Thu Jan 31, 2019 10:00 pm
  • We're only really good with simple "Why is the sky blue" type questions.
https://www.sciencealert.com/this-new-material-can-suck-all-the-oxygen-out-of-a-room wrote:
New material can suck all the oxygen out of a room
SCIENCEALERT STAFF 2 OCT 2014

<<Scientists from the University of Southern Denmark have developed a new form of crystalline cobalt salt that acts like a super-effective oxygen sponge. Once it sucks up oxygen, it will hold on to it indefinitely until it's gently heated or exposed to low oxygen pressure, at which point it will quietly release its oxygen hoard back out into the atmosphere. About 10 litres of it would be needed to suck all of the oxygen out of an average-sized room. "The material can absorb and release oxygen many times without losing the ability. It is like dipping a sponge in water, squeezing the water out of it and repeating the process over and over again,” said lead researcher and nanobioscience professor Christine McKenzie, in a press release. "When the substance is saturated with oxygen, it can be compared to an oxygen tank, containing pure oxygen under pressure. The difference is that this material can hold three times as much oxygen."

The key to the material’s success in trapping and holding such a large amount of oxygen molecules is its lattice crystalline structure, says Michael Byrne at Motherboard: "Each single crystal structure features two nitrate ions bound to a metallic molecular substructure, like a nitrogen house built on a cobalt foundation. It's really a nitrogen mobile home, however, as the introduction of oxygen to the neighbourhood means the nitrogen ions very quickly split town. The oxygen ions then set up shop themselves on the cobalt foundation."

Once the material is heated up or the pressure in the environment is lowered just enough, the oxygen will move back out into the atmosphere and the nitrogen will move back into the lattice structure of cobalt material.

The team is hoping to use the new material to replace hefty oxygen tanks used by scuba divers and mountain climbers, plus it could have a huge effect on medical treatments, such as for patients with Chronic obstructive pulmonary disease (COPD), which right now requires them to be hooked up to a large oxygen tank 24 hours a day. What the researchers envision is a small, simple oxygen mask made from oxygen-packed cobalt material that constantly replenishes its supply.

The research has been published in the journal Chemical Science.>>
Art, thank you for posting this. It is a lovely piece of wonderfully nerdy "How things work" info.

And of course you would be reading the journal Chemical Science.

Ann
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Re: APOD: Sharpless 308: Star Bubble (2019 Jan 31)

Post by MarkBour » Fri Feb 01, 2019 7:08 am

Oh yeah, I'm lugging a suitcase of cobalt up the mountain with me so I can breathe better up there.
I guess it's easier than having a Wolf-Rayett star in my pocket, hoping it will make a dolphin-shaped bubble of oxygen for me.
Mark Goldfain