Comments and questions about the
APOD on the main view screen.
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BDanielMayfield
- Don't bring me down
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by BDanielMayfield » Sun Nov 22, 2020 5:57 am
... 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.
This then is proof that not all stellar systems form in groups, some stars can and do form by themselves. Interesting. Is solo system formation rare or common?
Just as zero is not equal to infinity, everything coming from nothing is illogical.
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vdix
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by vdix » Sun Nov 22, 2020 11:00 am
500 light year away in that direction and there are no stars in front of it? That seems unlikely.
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BDanielMayfield
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by BDanielMayfield » Sun Nov 22, 2020 12:54 pm
vdix wrote: ↑Sun Nov 22, 2020 11:00 am
500 light year away in that direction and there are no stars in front of it? That seems unlikely.
But this cloud is very small as these objects go, being "only half a light year across." Something that small even at that distance could easily have no stars between us and it. Space is mostly empty. The average spacing between neighboring star systems around here is, what, about 5 ly or so.
Just as zero is not equal to infinity, everything coming from nothing is illogical.
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BDanielMayfield
- Don't bring me down
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by BDanielMayfield » Sun Nov 22, 2020 1:04 pm
BDanielMayfield wrote: ↑Sun Nov 22, 2020 12:54 pm
vdix wrote: ↑Sun Nov 22, 2020 11:00 am
500 light year away in that direction and there are no stars in front of it? That seems unlikely.
But this cloud is very small as these objects go, being "only half a light year across." Something that small even at that distance could easily have no stars between us and it. Space is mostly empty. The average spacing between neighboring star systems around here is, what, about 5 ly or so.
Plus this from the linked to wikipedia article on Barnard 68:
Barnard 68 is a molecular cloud, dark absorption nebula or Bok globule, towards the southern constellation Ophiuchus and well within our own galaxy at a distance of about 400 light-years, so close that not a single star can be seen between it and the Sun.
Just as zero is not equal to infinity, everything coming from nothing is illogical.
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BDanielMayfield
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by BDanielMayfield » Sun Nov 22, 2020 1:33 pm
Stellar density in solar neighborhood is only 0.004 stars per cubic light year
Stellar density is the average number of stars within a unit volume. It is similar to the stellar mass density, which is the total solar masses (MSun) found within a unit volume. Typically, the volume used by astronomers to describe the stellar density is a cubic parsec (pc3).
In the solar neighborhood, this value can be determined from surveys of nearby stars, combined with estimates of the number of faint stars that may have been missed. The true stellar density near the Sun is estimated as 0.004 stars per cubic light year, or 0.14 stars pc3.
The volume of a cone with a length of 400 LY and a base of 0.25 LY is only about 26 LY
3. The odds of a star being between us and an object as small as Barnard 68 is only 0.004*26 or about 0.104 to 1.
Last edited by
BDanielMayfield on Sun Nov 22, 2020 4:35 pm, edited 1 time in total.
Just as zero is not equal to infinity, everything coming from nothing is illogical.
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orin stepanek
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by orin stepanek » Sun Nov 22, 2020 1:53 pm
Kinda spooky little Twerp!
It's density is so amazing
that it hides all the stars behind it!
It is possible to look right through the cloud in infrared light.
I'd like to see a photo of that; (maybe I missed it!)
Orin
Smile today; tomorrow's another day!
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Chris Peterson
- Abominable Snowman
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Contact:
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by Chris Peterson » Sun Nov 22, 2020 2:26 pm
BDanielMayfield wrote: ↑Sun Nov 22, 2020 5:57 am
... 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.
This then is proof that not all stellar systems form in groups, some stars can and do form by themselves. Interesting. Is solo system formation rare or common?
The number of stars that form in a molecular cloud is determined by the mass of the cloud. This one is very small, at about three solar masses. But there is no suggestion that it will necessarily produce just a single star. That is enough mass to produce several stars, depending on how the material clumps as it collapses.
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E Fish
- Science Officer
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by E Fish » Sun Nov 22, 2020 3:34 pm
orin stepanek wrote: ↑Sun Nov 22, 2020 1:53 pm
barnard68v2_vlt_960.jpg
Kinda spooky little Twerp!
It's density is so amazing
that it hides all the stars behind it!
It is possible to look right through the cloud in infrared light.
I'd like to see a photo of that; (maybe I missed it!)
The ESO has a series of images of Barnard 68 in different wavelengths. B&W but still neat to see.
https://www.eso.org/public/images/eso9934b/
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jiharmer@hotmail.co.uk
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by jiharmer@hotmail.co.uk » Sun Nov 22, 2020 5:06 pm
Haven't we had this picture on APOD before ? Or am I just going completely bonkers ?
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De58te
- Commander
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by De58te » Sun Nov 22, 2020 5:48 pm
jiharmer@hotmail.co.uk wrote: ↑Sun Nov 22, 2020 5:06 pm
Haven't we had this picture on APOD before ? Or am I just going completely bonkers ?
2017, October 08. And the comments there said it was also from 2014, December 14.
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heehaw
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by heehaw » Sun Nov 22, 2020 6:07 pm
De58te wrote: ↑Sun Nov 22, 2020 5:48 pm
jiharmer@hotmail.co.uk wrote: ↑Sun Nov 22, 2020 5:06 pm
Haven't we had this picture on APOD before ? Or am I just going completely bonkers ?
2017, October 08. And the comments there said it was also from 2014, December 14.
I LOVE seeing a great APOD, such as this one, every so often!
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johnnydeep
- Commodore
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by johnnydeep » Sun Nov 22, 2020 6:29 pm
BDanielMayfield wrote: ↑Sun Nov 22, 2020 1:33 pm
Stellar density in solar neighborhood is only 0.004 stars per cubic light year
Stellar density is the average number of stars within a unit volume. It is similar to the stellar mass density, which is the total solar masses (MSun) found within a unit volume. Typically, the volume used by astronomers to describe the stellar density is a cubic parsec (pc3).
In the solar neighborhood, this value can be determined from surveys of nearby stars, combined with estimates of the number of faint stars that may have been missed. The true stellar density near the Sun is estimated as 0.004 stars per cubic light year, or 0.14 stars pc3.
The volume of a cone with a length of 400 LY and a base of 0.25 LY is only about 26 LY
3. The odds of a star being between us and an object as small as Barnard 68 is only 0.004*26 or about 0.104 to 1.
Thanks for that extra math! I too couldn't quite believe there were no stars between us and Barnard 68. BTW, I just double checked your local stellar density figure using numbers from
http://www.atlasoftheuniverse.com/250lys.html, which says there are about 260000 stars within 250 ly, which is 6.54e7 ly
3. That amounts to almost exactly .004 stars / ly
3. What a pleasant coincidence!
--
"To B̬̻̋̚o̞̮̚̚l̘̲̀᷾d̫͓᷅ͩḷ̯᷁ͮȳ͙᷊͠ Go......Beyond The F͇̤i̙̖e̤̟l̡͓d͈̹s̙͚ We Know."{ʲₒʰₙNYᵈₑᵉₚ}
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jiharmer@hotmail.co.uk
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by jiharmer@hotmail.co.uk » Sun Nov 22, 2020 6:38 pm
heehaw wrote: ↑Sun Nov 22, 2020 6:07 pm
De58te wrote: ↑Sun Nov 22, 2020 5:48 pm
jiharmer@hotmail.co.uk wrote: ↑Sun Nov 22, 2020 5:06 pm
Haven't we had this picture on APOD before ? Or am I just going completely bonkers ?
2017, October 08. And the comments there said it was also from 2014, December 14.
I LOVE seeing a great APOD, such as this one, every so often!
Thank you. Good to know that I'm not as crazy as I thought I was !
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BDanielMayfield
- Don't bring me down
- Posts: 2524
- Joined: Thu Aug 02, 2012 11:24 am
- AKA: Bruce
- Location: East Idaho
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by BDanielMayfield » Sun Nov 22, 2020 9:56 pm
johnnydeep wrote: ↑Sun Nov 22, 2020 6:29 pm
BDanielMayfield wrote: ↑Sun Nov 22, 2020 1:33 pm
Stellar density in solar neighborhood is only 0.004 stars per cubic light year
Stellar density is the average number of stars within a unit volume. It is similar to the stellar mass density, which is the total solar masses (MSun) found within a unit volume. Typically, the volume used by astronomers to describe the stellar density is a cubic parsec (pc3).
In the solar neighborhood, this value can be determined from surveys of nearby stars, combined with estimates of the number of faint stars that may have been missed. The true stellar density near the Sun is estimated as 0.004 stars per cubic light year, or 0.14 stars pc3.
The volume of a cone with a length of 400 LY and a base of 0.25 LY is only about 26 LY
3. The odds of a star being between us and an object as small as Barnard 68 is only 0.004*26 or about 0.104 to 1.
Thanks for that extra math! I too couldn't quite believe there were no stars between us and Barnard 68. BTW, I just double checked your local stellar density figure using numbers from
http://www.atlasoftheuniverse.com/250lys.html, which says there are about 260000 stars within 250 ly, which is 6.54e7 ly
3. That amounts to almost exactly .004 stars / ly
3. What a pleasant coincidence!
And I appreciate your appreciation Johnny. The source of my quotation and the figure 0.004 stars per LY was the wikipedia article Stellar Density, which I should have mentioned in my comment. I'd say that the coincidence is that both of us got our math right.
Just as zero is not equal to infinity, everything coming from nothing is illogical.
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BDanielMayfield
- Don't bring me down
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- Joined: Thu Aug 02, 2012 11:24 am
- AKA: Bruce
- Location: East Idaho
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by BDanielMayfield » Sun Nov 22, 2020 10:10 pm
In honor of all who mainly comment on what some object in an APOD looks like,
Perhaps it smells like a barnyard too. (All those aromatic hydrocarbons, etc.)
Just as zero is not equal to infinity, everything coming from nothing is illogical.
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orin stepanek
- Plutopian
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by orin stepanek » Mon Nov 23, 2020 3:07 am
E Fish wrote: ↑Sun Nov 22, 2020 3:34 pm
orin stepanek wrote: ↑Sun Nov 22, 2020 1:53 pm
barnard68v2_vlt_960.jpg
Kinda spooky little Twerp!
It's density is so amazing
that it hides all the stars behind it!
It is possible to look right through the cloud in infrared light.
I'd like to see a photo of that; (maybe I missed it!)
The ESO has a series of images of Barnard 68 in different wavelengths. B&W but still neat to see.
https://www.eso.org/public/images/eso9934b/
10-Q "E Fish" I like!
Orin
Smile today; tomorrow's another day!
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orin stepanek
- Plutopian
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- Joined: Wed Jul 27, 2005 3:41 pm
- Location: Nebraska
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by orin stepanek » Mon Nov 23, 2020 3:12 am
De58te wrote: ↑Sun Nov 22, 2020 5:48 pm
jiharmer@hotmail.co.uk wrote: ↑Sun Nov 22, 2020 5:06 pm
Haven't we had this picture on APOD before ? Or am I just going completely bonkers ?
2017, October 08. And the comments there said it was also from 2014, December 14.
The staff deserves a day off once in a while: so yes, Sundays are repeat days!
Orin
Smile today; tomorrow's another day!
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neufer
- Vacationer at Tralfamadore
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by neufer » Mon Nov 23, 2020 3:15 am
BDanielMayfield wrote: ↑Sun Nov 22, 2020 10:10 pm
In honor of all who mainly comment on what some object in an APOD looks like,
Perhaps it smells like a barnyard too. (All those aromatic hydrocarbons, etc.)
- A remnant of rector Poczobutt's Taurus Poniatovii
https://en.wikipedia.org/wiki/Taurus_Poniatovii wrote:
<<Taurus Poniatovii (Latin for Poniatowski's bull) was a constellation created by the former rector of Vilnius University, Marcin Odlanicki Poczobutt, in 1777 to honor Stanislaus Poniatowski, king of Poland. It consisted of stars that are today considered part of Ophiuchus and Aquila. It is no longer in use. It was wedged in between Ophiuchus, Aquila and Serpens Cauda. A depiction of the constellation can be found on the wall of the Vilnius University Astronomical Observatory.
The stars were picked for the resemblance of their arrangement to the Hyades group which form the "head" of Taurus. Before the definition of Taurus Poniatovii, some of these had been part of the obsolete constellation River Tigris. The brightest of these stars is 72 Oph (3.7 magnitude) in the "horn" of Taurus Poniatovii. The "face" of Taurus Poniatovii is formed by 67 Oph (4.0), 68 Oph (4.4) and 70 Oph (4.0).[1] The five brightest stars belong to loose open cluster Collinder 359 or Melotte 186.
Barn(y)ard's star is also inside the boundaries of this former constellation. Some minor stars (5th and 6th magnitude) now in Aquila formed the "rear" of Taurus Poniatovii.>>
Art Neuendorffer
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Jake
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by Jake » Wed Dec 02, 2020 5:01 pm
Photo from November 22, 2020 is a duplicate from December 19, 2004. You guys also need an updated “I’m not a robot” question, who wants to open new tabs and go back to try and find an editor’s name? I appreciate your times new roman 1995 internet look, it’s nostalgic for sure, but come on it’s 2020.