APOD: NGC 1499: The California Nebula (2023 Dec 19)

[APOD Robot]

NGC 1499: The California Nebula

Explanation: Could Queen Calafia'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 California, USA. Our Sun has its home within the Milky Way's Orion Arm, only about 1,000 light-years from the California Nebula. Also known as NGC 1499, the classic emission nebula is around 100 light-years long. On the featured image, the most prominent glow of the California Nebula is the red light characteristic of hydrogen atoms recombining with long lost electrons, stripped away (ionized) by energetic starlight. The star most likely providing the energetic starlight that ionizes much of the nebular gas is the bright, hot, bluish Xi Persei just to the right of the nebula. A regular target for astrophotographers, the California Nebula can be spotted with a wide-field telescope under a dark sky toward the constellation of Perseus, not far from the Pleiades.

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[Ann]

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.

The California Nebula and Xi Persei. Credit: Stephen Powell.

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The California Nebula and Xi Persei. Credit: Trevor Jones.

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I found a nice widefield image which put the California Nebula front and center:

Deep-sky objects in Taurus and Perseus. Credit: Trevor Jones.

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

IC 405 (right), IC 410 (left) and IC 417 (above left). Credit: Eemil Pietila.

IC 348 region in Perseus. View the full size! Credit: Thomas Henne.

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

Ann

[pferkul]

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

[Chris Peterson]

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

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

[johnnydeep]

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

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

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

[Fred the Cat]

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

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

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

Are you sure?

[johnnydeep]

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

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

Are you sure?

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 plus some matter.

[pferkul]

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

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

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.

[Chris Peterson]

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

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

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.

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.