Starship Asterisk*

The Bubble Nebula

Explanation: Blown by the wind from a massive star, this interstellar apparition has a surprisingly familiar shape. Cataloged as NGC 7635, it is also known simply as The Bubble Nebula. Although it looks delicate, the 10 light-year diameter bubble offers evidence of violent processes at work. Above and right of the Bubble's center is a hot, O star, several hundred thousand times more luminous and around 45 times more massive than the Sun. A fierce stellar wind and intense radiation from that star has blasted out the structure of glowing gas against denser material in a surrounding molecular cloud. The intriguing Bubble Nebula lies a mere 11,000 light-years away toward the boastful constellation Cassiopeia. This view of the cosmic bubble is composed of narrowband and broadband image data, capturing details in the emission region while recording a natural looking field of stars.

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Nice picture...
At 45 times the mass of the Sun...why has it not collapsed into a black hole, or blown up? Is it because of age? Still being young, and hot?

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Boomer12k wrote:
At 45 times the mass of the Sun...why has it not collapsed into a black hole, or blown up? Is it because of age? Still being young, and hot?

45 times the mass of the Sun is not an impossible "weight" for a star to carry for a short time. Say, for perhaps five million years or so.

I think that the most massive stars definitely identified contain about 120 times the mass of the Sun. Admittedly I haven't checked it up.
The fact that the star inside the Bubble Nebula is, indeed, blowing a bubble suggests that it is perhaps entering its Wolf-Rayet phase, when the O star starts blowing a ferocious wind. The picture on the left shows another extremely windy O star, HD 148937. The nebulosity seen on two sides of the star is classified as NGC 6164 and NGC 6165. The nebulae have been created by the star, whose hard wind blows gas away from itself. Then the onslaught of ultraviolet photons from the star ionizes the gas that it has blown away from itself. (But another important source of the ionization in this case is that the gas which is blown away by the star slams into the "gas background" further out, the so-called interstellar medium, and this collision between "bodies of gas" produces ionization.)

I think today's APOD looks brilliant, and I really like the mixture of narrowband and RGB imagery.

Boomer12k, your Bubble Nebula images aren't bad, either!

Ann

Nice description of the forces at work that create this strange and beautiful apparition. I was curious as to why Cassiopeia was described as "boastful" in the text. So, yet again, through APOD I've learned something I didn't know that I never knew . .
http://www.hawastsoc.org/deepsky/and/index.html#Myth
Thanks. Great picture!

Ahh! The beautiful bubble nebula!

That's no bubble... it's the face of a snake that's headed straight for us. My guess is Quatzaquatel.

Very neat picture.

It's interesting the star presumably causing this is off center. Is that perhaps because the bubble front involves a shock wave and the speed of "sound" is different in different parts of that region?

Tszabeau wrote:That's no bubble... it's the face of a snake that's headed straight for us. My guess is Quatzaquatel.

I thought that today, when I came back to read comments...it looks like an eel or something coming up behind the bubble....maybe he burped...

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INSIDE the bubble, on the left side, it looks like a guy standing there with a sword....

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nstahl wrote:Very neat picture.

It's interesting the star presumably causing this is off center. Is that perhaps because the bubble front involves a shock wave and the speed of "sound" is different in different parts of that region?

A likely reason is that the "surrounding gas" is thicker in one direction than in other directions. That's why the bubble can expand a lot more in some directions than in others.

Ann

Will that thing ever POP?

moonstruck wrote:
Will that thing ever POP?

Ah SpongeBob ... always in my heart.