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PostPosted: Mon, 01-05-17, 22:40 GMT 
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I recently learned of some research reported in late 2015 about some surprises about the local structure of the Milky Way which were discovered in the Hipparcos data:

http://sci.esa.int/hipparcos/56834-anot ... hitecture/

An interactive 3D display is available at http://sci.esa.int/hipparcos/ob-stars-interactive-hr/

Unfortunately, manipulating it is painfully slow on my computer, so I thought I'd try to represent some of the information in Celestia.

Below is a very preliminary result showing the spatial density of all of the B class stars in Celestia's database. Marks are colored red for the lowest density and white for the highest density, with intermediate values in yellow.

It shows at least one feature reported in the article referenced above: there's a trail of B stars between the Sun (in the center) and the Orion Nebula (near the lower edge). I dunno what the clumps toward the upper right might be associated with.

There are some other objects visible in this view. For example, pulsars are white crosses scattered across the image. The different types of symbols aren't really distinguishable at this resolution. I scaled down a 1920x1080 screengrab to 720x405.

Attachment:
ob_densities_small.jpg
ob_densities_small.jpg [ 57.68 KiB | Viewed 703 times ]

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PostPosted: Tue, 02-05-17, 12:43 GMT 
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Thanks a lot, Selden, for communicating these intriguing results/speculations.
My interest in locating the proper "messengers" to tell us about the MilkyWay structure in 2D and 3D is longstanding as you probably remember.

E.g. a summary:
viewtopic.php?f=11&t=875#p14522

Fridger

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PostPosted: Thu, 04-05-17, 20:40 GMT 
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Here's a preliminary version of the Addon. It marks the stars and shows some nearby non-stellar objects.


Attachments:
File comment: 401 KB expands to 2.7 MB
OB_Stars.zip [400.79 KiB]
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PostPosted: Sat, 06-05-17, 15:22 GMT 
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Selden, thanks for sharing! Nice!


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PostPosted: Sat, 06-05-17, 16:22 GMT 
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Selden wrote:
Here's a preliminary version of the Addon. It marks the stars and shows some nearby non-stellar objects.


Yes, thanks.

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PostPosted: Thu, 30-11-17, 21:52 GMT 
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Fascinating paper and addon. I would like to make a representation of Gould's Belt in Celestia, now. What should be best? A graticule of the kind you use for scale?

Guillermo

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PostPosted: Fri, 01-12-17, 3:38 GMT 
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I'm really not sure. Presumably it'd be nice to include some finer scale markings somehow.

I'm not sure if it's in the article mentioned previously, but I've read that Gaia distance measurements of stars in the OB associations are consistent with the Gould Belt not actually existing.

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PostPosted: Fri, 01-12-17, 12:45 GMT 
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Right, Selden, they mention it: the Belt is an effect of perpective of our view of the "streams". Gaia release 2 next year will surely shed some more light on this matter.

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PostPosted: Tue, 05-12-17, 17:18 GMT 
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Very nice addon Selden ... I especially like the graticules!

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PostPosted: Tue, 05-12-17, 20:40 GMT 
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CC,

Thanks for the kind words.

I published that graticule model almost 14 years ago. How time does fly! It's been used by a few people since then.

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PostPosted: Tue, 12-12-17, 14:41 GMT 
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Selden,

There is one update I'd like to suggest for the graticules, and that is to align the innermost 2 or 3 graticules with the Solar System ecliptic, rather than with the galactic plane.
In my mind it would be more useful for those graticules at the approximate scale of the solar-system, to be aligned with it.

I have a feeling you may have already published a standalone (single level) graticule for the solar-system a long time ago which actually was aligned with the ecliptic in this way. (I think it was red).

CC

PS.
Here's my (quick and dirty) patch:
Attachment:
OB_Stars_MOD.zip [672 Bytes]
Not downloaded yet

(overwrites GalacticPC.dsc ... my changes commented)

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PostPosted: Tue, 12-12-17, 20:28 GMT 
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My generic graticule Addon includes three sets of DSO graticule definitions, placing them with ecliptic, equatorial and galactic alignments.

See https://www.classe.cornell.edu/%7Eseb/c ... od-150.zip
at
https://www.classe.cornell.edu/%7Eseb/c ... les.html#2

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