by Ann » Thu Sep 29, 2011 9:00 am
Larry van Vleet, I absolutely agree with starstruck. That's a great image of yours, wonderfully deep and sharp.
I also love Manfred Schwarz' image of NGC 7129. It'sa very fine image, and the object, NGC 7129, is truly fascinating. It is mainly a reflection nebula, almost certainly lit up by stars of A and late class B stars. (I don't have my software here, so I can't check it up.) Anyway, stars of class A and late class B produce a lot of blue light, and when they are surrounded by dust, they can produce wonderful reflection nebulae. The best example of a reflection nebula around stars of class A or late class B is of course the Pleaides nebula.
However, the bright blue stars of the Pleaides are somewhat evolved. They are not newborn at all, but instead about a hundred million years old, and the nebula they are immersed in is not the nebula that gave birth to them. Instead, the dust cloud that is lit up by the Pleiades is a "chance encounter" in space! The cluster and the nebula just blundered into one another!
By contrast, the reflection nebula of NGC 7129 really is the nebula that gave birth to the stars. Therefore the stars are very young, probably only ten million years old or even younger. But it seems certain that the brightest blue stars are fully formed. My guess is that these blue stars may contain 2-3 solar masses each and thus be equivalents of Sirius and Vega.
Oh, but a truly fascinating aspect of this star forming region is the small red knots and arcs in the image. These little red structures testify so beautifully to the presence of low-mass star formation. They are caused by jets from low-mass stars that are in the process of forming. During this process, when unborn stars "put on meat" (or mass), they produce jets which light up the surrounding gas and makes it glow red from hydrogen emission. Later, when these low-mass stars are fully formed and have "settled down", they will not emit jets any more, and they will not ionize any hydrogen in their surroundings.
So these red structures are made of glowing hydrogen, ionized by the jets of unborn low-mass stars. How do we know these stars are going to be low of mass? We can know it because the red features are so small, and so completely overshadowed by the bright reflection nebula of stars that are probably at least twice as massive as the Sun, but which are still quite unable to ionize the hydrogen in their surroundings. And that's because they are fully formed and have stopped emitting jets.
If the stars that emit the jets that light up small red emission nebulae had been high-mass stars instead, the entire region would have been aglow with bright red emission nebulosity. But that's the difference between NGC 7129 and the Orion Nebula, for example: The stars that are forming in NGC 7129 are so small. So light-weight. The unborn stars of NGC 7129 can be called baby stars because of their youth, but they are also destined to remain little runts forever.
When I see that little red arc at about four o'clock in Manfred Schwarz' image, I want to say "Aaww! How cute! Cotchie-cotchie-coo, little baby star, you!"
Ann
And I just got myself 1945 posts.
War is over.Larry van Vleet, I absolutely agree with starstruck. That's a great image of yours, wonderfully deep and sharp.
I also love Manfred Schwarz' image of NGC 7129. It'sa very fine image, and the object, NGC 7129, is truly fascinating. It is mainly a reflection nebula, almost certainly lit up by stars of A and late class B stars. (I don't have my software here, so I can't check it up.) Anyway, stars of class A and late class B produce a lot of blue light, and when they are surrounded by dust, they can produce wonderful reflection nebulae. The best example of a reflection nebula around stars of class A or late class B is of course the Pleaides nebula.
However, the bright blue stars of the Pleaides are somewhat evolved. They are not newborn at all, but instead about a hundred million years old, and the nebula they are immersed in is not the nebula that gave birth to them. Instead, the dust cloud that is lit up by the Pleiades is a "chance encounter" in space! The cluster and the nebula just blundered into one another!
By contrast, the reflection nebula of NGC 7129 really is the nebula that gave birth to the stars. Therefore the stars are very young, probably only ten million years old or even younger. But it seems certain that the brightest blue stars are fully formed. My guess is that these blue stars may contain 2-3 solar masses each and thus be equivalents of Sirius and Vega.
Oh, but a truly fascinating aspect of this star forming region is the small red knots and arcs in the image. These little red structures testify so beautifully to the presence of low-mass star formation. They are caused by jets from low-mass stars that are in the process of forming. During this process, when unborn stars "put on meat" (or mass), they produce jets which light up the surrounding gas and makes it glow red from hydrogen emission. Later, when these low-mass stars are fully formed and have "settled down", they will not emit jets any more, and they will not ionize any hydrogen in their surroundings.
So these red structures are made of glowing hydrogen, ionized by the jets of unborn low-mass stars. How do we know these stars are going to be low of mass? We can know it because the red features are so small, and so completely overshadowed by the bright reflection nebula of stars that are probably at least twice as massive as the Sun, but which are still quite unable to ionize the hydrogen in their surroundings. And that's because they are fully formed and have stopped emitting jets.
If the stars that emit the jets that light up small red emission nebulae had been high-mass stars instead, the entire region would have been aglow with bright red emission nebulosity. But that's the difference between NGC 7129 and the Orion Nebula, for example: The stars that are forming in NGC 7129 are so small. So light-weight. The unborn stars of NGC 7129 can be called baby stars because of their youth, but they are also destined to remain little runts forever.
When I see that little red arc at about four o'clock in Manfred Schwarz' image, I want to say "Aaww! How cute! Cotchie-cotchie-coo, little baby star, you!"
Ann
And I just got myself 1945 posts. [url=http://www.youtube.com/watch?v=hb2YSAVHmIE]War is over.[/url]