SW galaxy size

SW galaxy is described as being "modest" sized galaxy.

-----ANH novel, ch. 6, page 87


"The tridimensional solid screen filled one wall of the vast chamber from floor to ceiling. It showed a million star systems. A tiny portion of the galaxy, but an impressive display nonetheless when exhibited in such a fashion."

Tarkin's speech to Leia from the ANH novel, ch. 7, page 116 :

"This station is the final link in the new-forged Imperial chain which will bind the million systems of the galactic Empire together once and for all."

After Alderaan's destruction, Vader checks the display again. From Chapter 8, page 129:

"Vader stared at the motley array of stars displayed on the conference-room map while Tarkin and Admiral Motti conferred nearby. Interestingly, the first use of the most powerful destructive machine ever constructed had seemingly had no influence at all on that map, which in itself represented only a tiny fraction of this section of one modest-sized galaxy.

It would take a microbreakdown of a portion of this map to reveal a slight reduction in spatial mass, caused by the disappearance of Alderaan. Alderaan, with its many cities, farms, factories, and towns -- and traitors, Vader reminded himself.

Despite his advances and intricate technological methods of annihilation, the actions of mankind remained unnoticeable to an uncaring, unimaginably vast universe." ----------

It is "modest-sized" (larger than small, but smaller than average) and we see from movie that it is spiral galaxy. However, it is NOT described as "modest-sized spiral galaxy".

Typical galaxies range from dwarfs with 10e7 stars, to giants with 10e14 stars. Our galaxy, with 2x10e11 to 4x10e11 stars is considered "large" galaxy. Its approx. volume is 7.85 x 10e12 cubic light years. It is 100 000 ly in diameter, with disk thickness from 2300 to 2600 ly.

So I would assign galaxies this classification:
giant - 10e12 to 10e14 stars
large - 10e11 to 10e12
medium - 10e10 to 10e11
modest - 10e9
small - 10e8
dwarf - 10e7

So Star Wars galaxy should have 10e9 stars, and density of 26 stars per 100 cubic light years, presuming it is similar to Milky Way. With that, we arrive at volume of 260 000 000 cubic light years. So it is only 3.2% of size of our galaxy in all directions - diameter should be 3200 and thickness 32 light years.

However, minimum diameter for spiral galaxy is 10 000 light years, so in end we have 10 000 ly for diameter, and 100 ly thickness. So entire Empire is 6% of Federation's size.

However, there is one interesting quote:

"BAIL ORGANA: It could be a trap.
OBI-WAN: No, I don't think so. The Chancellor will not be able to control the thousands of star systems without keeping the Senate intact."

Which means that Old Republic (and presumably Empire) had "thousands" of inhabited star systems, anywhere from 2 to 19 000. That implies much higher density than Federation has. If we take each world on average having 2 to 5 billion residents (given size of Coruscant, and fact that most Republic and Imperial worlds seemed to be lightly populated, with exception of Coruscant and Alderaan) it could give us 4 to 95 trillion residents, with higher values being more reasonable, if due to size of Coruscant itself.


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