Starship Asterisk*

by **Guest** » Thu Oct 02, 2014 7:47 pm

Chris Peterson wrote:
MarkBour wrote: the most accurate information comes from measuring the Doppler shifts of specific emission lines. Sometimes both can be used, since Doppler measurements give radial velocities, while optical/astrometric techniques give transverse velocities. Depending on the type of nebula, the two may or may not be the same (with the Bubble, they probably are).

If you have both, that is enough to give you the distance of the nebula (except for the worry about whether they are the same, of course)

by **geckzilla** » Thu Oct 02, 2014 7:46 pm

hoohaw wrote:Just to add to the confusion, take a look at the same nebula in a PREVIOUS apod incarnation: http://apod.nasa.gov/apod/ap131214.html
looks like a mirror image, to me. (Maybe taken from the other side of the Universe?)

Yep, it happens. I don't like it when astrophotographers present things mirrored. I can forgive it when they're not north up but mirroring it adds a lot of unnecessary confusion.

by **hoohaw** » Thu Oct 02, 2014 7:43 pm

Just to add to the confusion, take a look at the same nebula in a PREVIOUS apod incarnation: http://apod.nasa.gov/apod/ap131214.html
looks like a mirror image, to me. (Maybe taken from the other side of the Universe?)

by **starsurfer** » Mon Dec 16, 2013 9:52 am

Galaxian wrote:Hug some one you love. A hug is a great gift, one size fits all and you can return it to the giver, repeatedly.

i whole heartedly agree with this statement!

(seriously there needs to be a love heart smilie!)

by **Chris Peterson** » Sat Dec 14, 2013 11:31 pm

MarkBour wrote:I'm assuming that one of the things that is easy to do with these nebula is to determine the rate of expansion of the bubble.
There are lots of things that appear to be hard to directly observe in astronomy, but that one seems very straightforward.
I mean, we can just image it twice, like 10 years apart, and we should see a significant difference, right?

Yes, but the most accurate information comes from measuring the Doppler shifts of specific emission lines. Sometimes both can be used, since Doppler measurements give radial velocities, while optical/astrometric techniques give transverse velocities. Depending on the type of nebula, the two may or may not be the same (with the Bubble, they probably are).

by **MarkBour** » Sat Dec 14, 2013 11:08 pm

I'm assuming that one of the things that is easy to do with these nebula is to determine the rate of expansion of the bubble.
There are lots of things that appear to be hard to directly observe in astronomy, but that one seems very straightforward.
I mean, we can just image it twice, like 10 years apart, and we should see a significant difference, right?

by **geckzilla** » Sat Dec 14, 2013 9:48 pm

I don't know how you can conflate Sagan's imaginative science fiction with the nebula model. One is all in Sagan's head while the other is an undeniably flawed but fun extrapolation of how a nebula might look if we could zip around it at many times the speed of light to see its structure. Chris is right about it creating bias, too. Once you've seen someone else's take on an object like that it's really hard to see it any other way.

by **Galaxian** » Sat Dec 14, 2013 9:39 pm

Chris Peterson wrote:
Coil_Smoke wrote:Wow, Thanks for posting the link to the 3D imaging of The Bubble nebula.The 3D image is amazinghttp://astroanarchy.blogspot.fi/2013/02 ... ebula.html. There have been so many astronomical images of planetary nebula that could benefit from this process.
Nothing benefits from this technique. It is entirely bogus. An invented 3D model with an astronomical image painted onto it.

If you're at all interested in understanding these sorts of objects, you should avoid these fake 3D "reconstructions", which are more likely to bias your understanding than to clarify anything.

Parting shot: I have seen Professor Sagan on TV explaining how a dandelion seed spacecraft could manoeuvre around the solar system. That was real, I take it? He really owned a dandelion seed spaceship? It wasn't something "bogus". No, it wouldn't have been, Professor Sagan was a professional. They wouldn't fake stuff. Especially not fake 3d "reconstructions". So when he shows us the core of Jupiter we can take it entirely as true and the gospel of a professional Professor that he went there with cameras?

Enough from me and far too much.
Enjoy Christmas, everyone. Hug some one you love. A hug is a great gift, one size fits all and you can return it to the giver, repeatedly.

by **Anthony Barreiro** » Sat Dec 14, 2013 5:21 pm

Chris Peterson wrote:
Coil_Smoke wrote:Wow, Thanks for posting the link to the 3D imaging of The Bubble nebula.The 3D image is amazinghttp://astroanarchy.blogspot.fi/2013/02 ... ebula.html. There have been so many astronomical images of planetary nebula that could benefit from this process.
Nothing benefits from this technique. It is entirely bogus. An invented 3D model with an astronomical image painted onto it.

If you're at all interested in understanding these sorts of objects, you should avoid these fake 3D "reconstructions", which are more likely to bias your understanding than to clarify anything.

Oh darn. I was completely captivated by this animation! But now I know, if I ever travel to the Bubble nebula: check the gps, don't trust the map.

But seriously, for a casual viewer, engaging eye candy, even if it takes liberties that offend the cognoscenti, can be the hook that leads to further study and greater understanding.

by **geckzilla** » Sat Dec 14, 2013 3:43 pm

To be fair, J-P makes it very clear that the 3D model is an artistic reconstruction and a lot of guess work. But I do also think that a lot of people think they are "real" and perhaps more scientific than they are.

My favorite planetary nebula models are simulations. Vincent apparently managed to predict conical structures would be present in the Red Rectangle before Hubble took its images of the thing. Interesting.

by **Chris Peterson** » Sat Dec 14, 2013 3:28 pm

Coil_Smoke wrote:Wow, Thanks for posting the link to the 3D imaging of The Bubble nebula.The 3D image is amazinghttp://astroanarchy.blogspot.fi/2013/02 ... ebula.html. There have been so many astronomical images of planetary nebula that could benefit from this process.

Nothing benefits from this technique. It is entirely bogus. An invented 3D model with an astronomical image painted onto it.

If you're at all interested in understanding these sorts of objects, you should avoid these fake 3D "reconstructions", which are more likely to bias your understanding than to clarify anything.

by **starsurfer** » Sat Dec 14, 2013 12:58 pm

Coil_Smoke wrote:
starsurfer wrote:Ahhh, this is NOT a Wolf Rayet nebula!!

I would also like to say that I love Wolf Rayet nebulae! There really should be a "love heart" smilie!
I had to look that one up. I found this about that. 'Wolf Rayet' star http://imagine.gsfc.nasa.gov/docs/ask_a ... 0603a.html
And this APOD image...

Some people might find my slightly cryptic comment a bit confusing! One thing that annoys me is that many people still describe the Bubble Nebula as a Wolf Rayet nebula when in fact it is produced by an O-type star.
I'm a big fan of Wolf Rayet nebulae, the image you linked to is the southern Wolf Rayet nebula NGC 3199, a false colour image taken by Ken Crawford, which was also on APOD. You can see the original image here: http://www.imagingdeepsky.com/Nebulae/N ... GC3199.htm
I prefer it in true colour with lovely shades of pink and purple, I love this image by Marco Lorenzi: http://www.glitteringlights.com/Images/ ... -7N2VrSJ/A

by **Coil_Smoke** » Sat Dec 14, 2013 9:58 am

starsurfer wrote:Ahhh, this is NOT a Wolf Rayet nebula!!

I would also like to say that I love Wolf Rayet nebulae! There really should be a "love heart" smilie!

I had to look that one up. I found this about that. 'Wolf Rayet' star http://imagine.gsfc.nasa.gov/docs/ask_a ... 0603a.html
And this APOD image...

by **Coil_Smoke** » Sat Dec 14, 2013 9:41 am

Wow, Thanks for posting the link to the 3D imaging of The Bubble nebula.The 3D image is amazinghttp://astroanarchy.blogspot.fi/2013/02 ... ebula.html. There have been so many astronomical images of planetary nebula that could benefit from this process. The web site http://astroanarchy.blogspot.fi/ states there is some trickery involved in developing the video. That due to the vast distance involved there is [currently] no parallax information available generate such an image. Imagine the future of space based optical interferometry. I have always wondered if many apparently "Round" planetary nebula have "Ant Nebula"http://apod.nasa.gov/apod/ap100425.html like structure but are just being viewed end on.

by **starsurfer** » Sat Dec 14, 2013 8:01 am

Ahhh, this is NOT a Wolf Rayet nebula!!

Also narrowband filters are better than narrowband for nebulae (and even galaxies) that contain Ha and OIII emission. I think the best images are the ones that combine narrow (Ha and OIII) and broad (LRGB).

I would also like to say that I love Wolf Rayet nebulae! There really should be a "love heart" smilie!

by **Ann** » Sat Dec 14, 2013 6:24 am

Today's APOD brings out details in the ionized gas around the hot star that can only be revealed through narrowband imaging.

Other things can be revealed through broadband photography. This image gives us a better idea of what the scene would look like to our eyes, if our eyes were many, many times more sensitive to faint light than they are.

Ann

by **Boomer12k** » Sat Dec 14, 2013 5:26 am

My photo is much fainter, and I only get a Crescent shape of part of a bubble, but still an interesting object....guess I need to get some Filters...

Decent picture of it...
The 3d Depiction is interesting....close up, the inner material, if viewed just right, looks like a Man standing in front of, and looking up, at a lit up Orb...

:---[===] *

by **APOD Robot** » Sat Dec 14, 2013 5:06 am

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 natural looking view of the cosmic bubble is composed from narrowband image data, also used to create a 3D model.

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