Add 1 MILLION stars in M31 (Andromeda's galaxy) !

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Cham M
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Add 1 MILLION stars in M31 (Andromeda's galaxy) !

Post #1by Cham » 12.08.2016, 19:26

I'm publishing a file of ONE MILLION stars for the Andromeda galaxy (M31) ! :eek:

Warning ! This file will slow down the startup process of Celestia, and also may have an impact in the selection field. However, it is pretty smooth in 3D space (at least on my 6 years old system).

Since all the stars in this file are random, you can easily trim down the file by keeping any number of stars you want, if 1 000 000 stars is too much pressure for your system.

Take note that all the stars in this distribution are very luminous fictious stars, so we could see them in Celestia, at a reasonable distance. Their Absolute Magnitude and Spectral Class are from Celestia's default database, so they are realistic luminous stars. Most of them are on the main sequence branch, on a Hertzsprung-Russell diagram.

This addon could be usefull to make nice pictures of a starry night.

Have fun !

M31-1Million_stars.stc.zip
(29.85 MiB) Downloaded 374 times
(31 MB zip file)

Preview (with stars luminosity option set to max) :
MegaM31.jpg


Added after 9 minutes 12 seconds:
Just for the fun. The Mega stars file above mixes very well with some 3D nebulae. Here are 2 examples to show off :
Neb1.jpg

Neb2.jpg


Added after 14 minutes 15 seconds:
A fictious stellar system, in Andromeda, with the 1 million stars database :
andromeda.jpg
Last edited by Cham on 13.08.2016, 15:18, edited 1 time in total.
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Post #2by john71 » 13.08.2016, 10:27

I know I'm getting boring, but if 1 million star is slowing down Celestia, how can we use the 1 BILLION Gaia star data coming up at 14 september? :cry:

http://sci.esa.int/gaia/58042-mark-your-calendar- ... -release-set-for-14-september/

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Post #3by Cham » 13.08.2016, 12:34

If they release 1 billion stars, we'll have a choice problem. Which star to use from the whole database ?
"Well! I've often seen a cat without a grin", thought Alice; "but a grin without a cat! It's the most curious thing I ever saw in all my life!"

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Post #4by john71 » 13.08.2016, 12:49

I read somewhere, that if the database is organized in octree, this allows it to handle hundreds of billions stars and the interactive choosing of visible ones. Celestia has this ability...

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Post #5by selden » 13.08.2016, 13:02

"Slowing down" is relative. What matters is how much it slows down on your computer.

There are two parts of being slow: slow to load and slow to draw. "Slow to load" can be improved by using a more compact file. "Slow to draw" depends on the efficiency of Celestia's software and the performance of your hardware. Getting a faster CPU and graphics hardware is one way to improve the drawing speed. You also can adjust how much Celestia draws. For example, it'll run more quickly if you reduce the number of objects visible in its window.

Cham's stars are relatively slow to load because they are defined using Celestia's textual STar Catalog files. They use many characters (bytes) to define each star.

Celestia also uses a binary star catalog format which uses the minimum number of bytes needed to define each star. As a result, it loads much more quickly than an STC catalog which defines the same number of stars. Unfortunately, Celestia currently supports the use of only one file of binary star information: stars.dat in the data directory. When you can replace it, the replacement needs to include the Hipparcos catalog, too, if you want to be able to see them.

There are two replacements for stars.dat available on the MotherLode. One defines about 1 million stars and the other defines about 2 million stars. They're available at http://celestiamotherlode.net/catalog/extrasolar_stars.php Search for Star Databases on that page.

There is a perl script available in Celestia's archive on SourceForge which you can use to create your own stars.dat. See https://sourceforge.net/p/celestia/code/HEAD/tree/trunk/celestia/src/tools/stardb/

As I mentioned before, Celestia already organizes its stars using octrees in order to minimize its drawing time and storage. The current limits in the number of stars and objects it can manage are the result of using 32 bit addressing. Some rewriting would be needed for Celestia to be able to take full advantage of 64 bit addressing.
Selden

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Post #6by Goofy » 13.08.2016, 13:08

Thank you, Cham, even if so many stars almost disappear in that huge galaxy.
Bye
Goofy :smile:
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Post #7by john71 » 13.08.2016, 13:13

I think using more binary star sources or 64 bit addressing would be nice...

By the way, as I know the 2 million stars Tycho catalogue is not very accurate. There will be in September a Gaia release of reworked Tycho catalogue of these stars: "In addition, for a subset of data – about 2 million stars in common between the Tycho-2 Catalogue and Gaia – there will be a five-parameter astrometric solution, giving the positions, parallaxes, and proper motions for those objects. This is referred to as the Tycho-Gaia Astrometric Solution (TGAS)."

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Post #8by SVision » 13.08.2016, 14:57

Cham, great job :smile: ! Here is my selection of screenshots of Your add-on . It looks very impressive :eek: My supplement with 500 maksmimum stars (M 110) to the local group of galaxies fade with these dimensions :sad: ...
Image
Image
Image
Yes .Indeed addon is very heavy load on the computer, but it is true noticed Selden it depends on the iron.I would like you to know about this adon. This is the real star? That is, it is a scientific information or is based on this addon generated by stars?
If this is the real star is where you got information about them ?

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Post #9by john71 » 13.08.2016, 14:59

As I know we can't see individual stars in M31.

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Post #10by Cham » 13.08.2016, 15:15

All of these stars are fictious (we don't know much stars of M31, in reality).

The stars in this file were generated randomly, using a mathematical algorithm. However, they have realistic Abs Mag and Spectral Class. As I said in my first message above, all these stars are very luminous fictious stars, mostly on the Main Sequence on a HR diagram.

There is no dwarfs, no pulsars, no white dwarfs in this file, because we couldn't see them in Celestia (unless we are very very close to them, of course).
"Well! I've often seen a cat without a grin", thought Alice; "but a grin without a cat! It's the most curious thing I ever saw in all my life!"

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Post #11by SVision » 13.08.2016, 15:37

john71 wrote:As I know we can't see individual stars in M31.
john71,depending on the size of the telescope and its resolution. For example using the 100-inch (?2.5 meter) Hooker Telescope on symmetrical English yoke mount with Edwin Hubble spent his studies. He also investigated the Cepheids Andromeda and Triangulum galaxies. In modern science in asenale studies have much sensitivity and more powerful tools than those that were available to astronomers in the 20th century. That only is the Hubble Space Telescope and the receiver space telescope named James the Web :wink: .
Cham, you understand . I agree with you. We still know little about the stellar population of the galaxy . By the way. I think that you might be interested in this
This generator globular clusters .If you are interested in it you can contact the author
Another question: Do you mind if I add to your addon real star?

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Post #12by Cham » 13.08.2016, 15:55

SVision,

you can do wathever you want with all of my addons. I'm giving them away for you all to play with Celestia.

So modify them as you wish. I'll be glad if my work (done for my personal little person) could also be usefull to others too.

About stellar generators, I really don't need any from elsewhere. My Mathematica codes can do any kind of stellar distributions, for any galaxy in the local group. I just need to feed them with a few parameters (mostly location and orientation, and number of stars I want).

Added after 2 minutes 19 seconds:
If someone want a stupid mess of 10 millions stars for a small galaxy in the local group, I could do it pretty easily. :lol: :drunk:
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Post #13by SVision » 13.08.2016, 16:16

Cham wrote:you can do wathever you want with all of my addons. I'm giving them away for you all to play with Celestia.
So modify them as you wish. I'll be glad if my work (done for my personal little person) could also be usefull to others too.
Cham wrote:About stellar generators, I really don't need any from elsewhere. My Mathematica codes can do any kind of stellar distributions, for any galaxy in the local group. I just need to feed them with a few parameters (mostly location and orientation, and number of stars I want).
Good Cham :smile: .
Last edited by SVision on 13.08.2016, 19:17, edited 1 time in total.

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Post #14by john71 » 13.08.2016, 18:31

SVision: of course we can see galaxies, what I meant was we cannot see the individual stars in M31, like we can see them in the Milky Way. We cannot measure their distance etc. one by one, because we only see their combined light, not the individual objects.

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Post #15by selden » 13.08.2016, 20:17

John,

We can see some of the stars in M31 as individual objects. While we can't use parallax to measure their individual distances, the distances to some of them (like Cepheid variables) can be measured in other ways.

http://hubblesite.org/newscenter/archive/releases/2015/02/image/a/
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Post #16by john71 » 14.08.2016, 06:20

Selden, thanks, I didn't know that! Cepheid variable stars are amazing!!!


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