Starship Asterisk*

[quote=pferkul post_id=335779 time=1703104520 user_id=128650]
[quote="Chris Peterson" post_id=335769 time=1703029967 user_id=117706]
[quote=pferkul post_id=335768 time=1703029643 user_id=128650]
Are there any estimates of the mass or average density of the California Nebula, and the average density of its surrounding medium?
[/quote]

The mass is probably that of several tens of Suns. The density is that of a very hard vacuum.
[/quote]

I know the density of interstellar space can vary greatly, but using an "interstellar space" density of one hydrogen atom per cc, then 1000 cubic light years contains about one solar mass. Assume the California Nebula spans 100 light years in diameter. The "interstellar space" mass of this volume is about 1,000 solar masses.

So when we are viewing the California Nebula, are we just seeing slightly concentrated filaments? If the average density of the California nebula was only 1% higher than the surrounding media (i.e., 1.01 H atoms per cc) this would amount to 10 additional solar masses.
[/quote]
I think any background mass is removed when considering the mass of a nebula. Or to put it a little differently, empty space is treated as being truly empty.

[quote="Chris Peterson" post_id=335769 time=1703029967 user_id=117706]
[quote=pferkul post_id=335768 time=1703029643 user_id=128650]
Are there any estimates of the mass or average density of the California Nebula, and the average density of its surrounding medium?
[/quote]

The mass is probably that of several tens of Suns. The density is that of a very hard vacuum.
[/quote]

I know the density of interstellar space can vary greatly, but using an "interstellar space" density of one hydrogen atom per cc, then 1000 cubic light years contains about one solar mass. Assume the California Nebula spans 100 light years in diameter. The "interstellar space" mass of this volume is about 1,000 solar masses.

So when we are viewing the California Nebula, are we just seeing slightly concentrated filaments? If the average density of the California nebula was only 1% higher than the surrounding media (i.e., 1.01 H atoms per cc) this would amount to 10 additional solar masses.

[quote="Fred the Cat" post_id=335776 time=1703094652 user_id=143303]
[quote=johnnydeep post_id=335774 time=1703082854 user_id=132061]
[quote="Chris Peterson" post_id=335769 time=1703029967 user_id=117706]


The mass is probably that of several tens of Suns. The density is that of a very hard vacuum.
[/quote]

And no doubt, the density of the surrounding medium is less dense still!
[/quote]
Are you [url=https://math.ucr.edu/home/baez/vacuum.html] [i]sure[/i][/url]? :|
[/quote]

Yes. We're talking about (non virtual) particle density here not vacuum energy density. Which you already knew. 😊 And even if both were included, surely the total energy density in a complete vacuum would be less than that in a complete vacuum [i][b]plus [/b][/i]some matter.

[quote=johnnydeep post_id=335774 time=1703082854 user_id=132061]
[quote="Chris Peterson" post_id=335769 time=1703029967 user_id=117706]
[quote=pferkul post_id=335768 time=1703029643 user_id=128650]
Are there any estimates of the mass or average density of the California Nebula, and the average density of its surrounding medium?
[/quote]

The mass is probably that of several tens of Suns. The density is that of a very hard vacuum.
[/quote]

And no doubt, the density of the surrounding medium is less dense still!
[/quote]
Are you [url=https://math.ucr.edu/home/baez/vacuum.html] [i]sure[/i][/url]? :|

[quote="Chris Peterson" post_id=335769 time=1703029967 user_id=117706]
[quote=pferkul post_id=335768 time=1703029643 user_id=128650]
Are there any estimates of the mass or average density of the California Nebula, and the average density of its surrounding medium?
[/quote]

The mass is probably that of several tens of Suns. The density is that of a very hard vacuum.
[/quote]

And no doubt, the density of the surrounding medium is less dense still!

[quote=pferkul post_id=335768 time=1703029643 user_id=128650]
Are there any estimates of the mass or average density of the California Nebula, and the average density of its surrounding medium?
[/quote]

The mass is probably that of several tens of Suns. The density is that of a very hard vacuum.

Are there any estimates of the mass or average density of the California Nebula, and the average density of its surrounding medium?

Because I'm the Color Commentator, I'm posting the APOD side by side with another picture of the California Nebula and ionizing star Xi Persei. I like one of them better than the other.


[float=left][img3="The California Nebula and Xi Persei. Credit: Stephen Powell."]https://apod.nasa.gov/apod/image/2312/CalNeb_Powell_960.jpg[/img3][/float][float=right][img3="The California Nebula and Xi Persei. Credit: Trevor Jones."]https://astrobackyard.com/wp-content/uploads/2022/11/california-nebula-through-telescope.jpg[/img3][/float]
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I found a nice widefield image which put the California Nebula front and center:


[float=left][img3="Deep-sky objects in Taurus and Perseus. Credit: Trevor Jones."]https://astrobackyard.com/wp-content/uploads/2019/09/deep-sky-astrophotography-star-tracker.jpg[/img3][/float][float=right][attachment=2]California Nebula and friends Trevor Jones annotated.png[/attachment][/float]
[clear][/clear]


Let's have a closeup of some of the sights, shall we?


[float=left][attachment=1]IC 405 IC 410 and IC 417 Eemil Pietila.png[/attachment][c][size=85][color=#0040FF]IC 405 (right), IC 410 (left) and IC 417 (above left). Credit: Eemil Pietila.[/color][/size][/c][/float] [float=right][attachment=0]IC 348 region in Perseus large Thomas Henne.png[/attachment][c][size=85][color=#0040FF]IC 348 region in Perseus. View the full size! Credit: Thomas Henne.[/color][/size][/c][/float]
[clear][/clear]



There is a treasure trove of beautiful objects in the part of the sky, and there are lovely pictures of these beautiful objects, too! :D

Ann

[url=https://apod.nasa.gov/apod/ap231219.html] [img]https://apod.nasa.gov/apod/calendar/S_231219.jpg[/img] [size=150]NGC 1499: The California Nebula[/size][/url]

[b] Explanation: [/b] Could [url=https://en.wikipedia.org/wiki/Calafia]Queen Calafia[/url]'s mythical island exist in space? Perhaps not, but by chance the outline of this molecular space cloud echoes the outline of the state of [url=https://en.wikipedia.org/wiki/California]California[/url], USA. Our [url=https://apod.nasa.gov/apod/ap140506.html]Sun[/url] has its home within the Milky Way's [url=http://www.atlasoftheuniverse.com/5000lys.html]Orion Arm[/url], only about 1,000 light-years from the [url=https://en.wikipedia.org/wiki/California_Nebula]California Nebula[/url]. Also known as [url=https://spider.seds.org/spider/Misc/n1499.html]NGC 1499[/url], the classic emission nebula is around 100 [url=https://starchild.gsfc.nasa.gov/docs/StarChild/questions/question19.html]light-year[/url]s long. On the [url=https://www.instagram.com/p/C0xJ8JdpPrb/]featured image[/url], the most prominent glow of the California Nebula is the red light characteristic of [url=https://periodic.lanl.gov/1.shtml]hydrogen[/url] atoms recombining with [url=https://apod.nasa.gov/apod/lib/lament.html]long lost[/url] electrons, stripped away ([url=https://energyeducation.ca/wiki/images/3/3d/IONIZATION.png]ionized[/url]) by energetic starlight. The star most likely providing the [url=https://science.nasa.gov/ems/10_ultravioletwaves]energetic starlight[/url] that [url=https://spaceplace.nasa.gov/ion-balloons/en/]ionizes[/url] much of the nebular gas is the bright, hot, bluish [url=https://en.wikipedia.org/wiki/Xi_Persei]Xi Persei[/url] just to the right of the nebula. A regular target for astrophotographers, the California Nebula [url=https://apod.nasa.gov/apod/ap090411.html]can be spotted[/url] with a wide-field telescope under a dark sky toward the constellation of [url=https://en.wikipedia.org/wiki/Perseus_%28constellation%29]Perseus[/url], not far from the [url=https://apod.nasa.gov/apod/ap220405.html]Pleiades[/url].


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